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  • 1
    Unknown
    Paris : OECD
    Keywords: risk assessment
    Description / Table of Contents: Recent global shocks, such as the 2008 financial crisis, have driven policy makers and industry strategists to re-examine how to prepare for and respond to events that can begin locally and propagate around the world with devastating effects on society and the economy. This report considers how the growing interconnectedness in the global economy could create the conditions and vectors for rapid and widespread disruptions. It looks at examples of hazards and threats that emerge from the financial world, cyberspace, biological systems and even the solar system, to reflect on what strategic capacities are called for to improve assessment, mapping, modelling, response and resilience to such large scale risks.
    Pages: Online-Ressource (137 Seiten)
    ISBN: 9789264114586
    Language: English
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Risk analysis 19 (1999), S. 527-545 
    ISSN: 1539-6924
    Keywords: breast-feeding ; chlorinated compounds ; risk assessment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Exposure to persistent organochlorines in breast milk was estimated probabilistically for Canadian infants. Noncancer health effects were evaluated by comparing the predicted exposure distributions to published guidance values. For chemicals identified as potential human carcinogens, cancer risks were evaluated using standard methodology typically applied in Canada, as well as an alternative method developed under the Canadian Environmental Protection Act. Potential health risks associated with exposure to persistent organochlorines were quantitatively and qualitatively weighed against the benefits of breast-feeding. Current levels of the majority of contaminants identified in Canadian breast milk do not pose unacceptable risks to infants. Benefits of breast-feeding are well documented and qualitatively appear to outweigh potential health concerns associated with organochlorine exposure. Furthermore, the risks of mortality from not breast-feeding estimated by Rogan and colleagues exceed the theoretical cancer risks estimated for infant exposure to potential carcinogens in Canadian breast milk. Although levels of persistent compounds have been declining in Canadian breast milk, potentially significant risks were estimated for exposure to polychlorinated biphenyls, dibenzo-p-dioxins, and dibenzofurans. Follow-up work is suggested that would involve the use of a physiologically based toxicokinetic model with probabilistic inputs to predict dioxin exposure to the infant. A more detailed risk analysis could be carried out by coupling the exposure estimates with a dose–response analysis that accounts for uncertainty.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Risk analysis 19 (1999), S. 689-701 
    ISSN: 1539-6924
    Keywords: risk ; risk perception ; risk assessment ; risk communication ; risk management
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Risk management has become increasingly politicized and contentious. Polarized views, controversy, and conflict have become pervasive. Research has begun to provide a new perspective on this problem by demonstrating the complexity of the concept “risk” and the inadequacies of the traditional view of risk assessment as a purely scientific enterprise. This paper argues that danger is real, but risk is socially constructed. Risk assessment is inherently subjective and represents a blending of science and judgment with important psychological, social, cultural, and political factors. In addition, our social and democratic institutions, remarkable as they are in many respects, breed distrust in the risk arena. Whoever controls the definition of risk controls the rational solution to the problem at hand. If risk is defined one way, then one option will rise to the top as the most cost-effective or the safest or the best. If it is defined another way, perhaps incorporating qualitative characteristics and other contextual factors, one will likely get a different ordering of action solutions. Defining risk is thus an exercise in power. Scientific literacy and public education are important, but they are not central to risk controversies. The public is not irrational. Their judgments about risk are influenced by emotion and affect in a way that is both simple and sophisticated. The same holds true for scientists. Public views are also influenced by worldviews, ideologies, and values; so are scientists' views, particularly when they are working at the limits of their expertise. The limitations of risk science, the importance and difficulty of maintaining trust, and the complex, sociopolitical nature of risk point to the need for a new approach—one that focuses upon introducing more public participation into both risk assessment and risk decision making in order to make the decision process more democratic, improve the relevance and quality of technical analysis, and increase the legitimacy and public acceptance of the resulting decisions.
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  • 4
    Electronic Resource
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    Springer
    Risk analysis 19 (1999), S. 711-726 
    ISSN: 1539-6924
    Keywords: variability ; exposure ; susceptibility ; risk assessment ; pharmacokinetics ; pharmacodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract This paper reviews existing data on the variability in parameters relevant for health risk analyses. We cover both exposure-related parameters and parameters related to individual susceptibility to toxicity. The toxicity/susceptibility data base under construction is part of a longer term research effort to lay the groundwork for quantitative distributional analyses of non-cancer toxic risks. These data are broken down into a variety of parameter types that encompass different portions of the pathway from external exposure to the production of biological responses. The discrete steps in this pathway, as we now conceive them, are: •Contact Rate (Breathing rates per body weight; fish consumption per body weight) •Uptake or Absorption as a Fraction of Intake or Contact Rate •General Systemic Availability Net of First Pass Elimination and Dilution via Distribution Volume (e.g., initial blood concentration per mg/kg of uptake) •Systemic Elimination (half life or clearance) •Active Site Concentration per Systemic Blood or Plasma Concentration •Physiological Parameter Change per Active Site Concentration (expressed as the dose required to make a given percentage change in different people, or the dose required to achieve some proportion of an individual's maximum response to the drug or toxicant) •Functional Reserve Capacity–Change in Baseline Physiological Parameter Needed to Produce a Biological Response or Pass a Criterion of Abnormal Function Comparison of the amounts of variability observed for the different parameter types suggests that appreciable variability is associated with the final step in the process–differences among people in “functional reserve capacity.” This has the implication that relevant information for estimating effective toxic susceptibility distributions may be gleaned by direct studies of the population distributions of key physiological parameters in people that are not exposed to the environmental and occupational toxicants that are thought to perturb those parameters. This is illustrated with some recent observations of the population distributions of Low Density Lipoprotein Cholesterol from the second and third National Health and Nutrition Examination Surveys.
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  • 5
    Electronic Resource
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    Springer
    Risk analysis 19 (1999), S. 763-807 
    ISSN: 1539-6924
    Keywords: risk assessment ; probabilistic risk assessment ; performance assessment ; policy analysis ; history of technology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract This article describes the evolution of the process for assessing the hazards of a geologic disposal system for radioactive waste and, similarly, nuclear power reactors, and the relationship of this process with other assessments of risk, particularly assessments of hazards from manufactured carcinogenic chemicals during use and disposal. This perspective reviews the common history of scientific concepts for risk assessment developed until the 1950s. Computational tools and techniques developed in the late 1950s and early 1960s to analyze the reliability of nuclear weapon delivery systems were adopted in the early 1970s for probabilistic risk assessment of nuclear power reactors, a technology for which behavior was unknown. In turn, these analyses became an important foundation for performance assessment of nuclear waste disposal in the late 1970s. The evaluation of risk to human health and the environment from chemical hazards is built on methods for assessing the dose response of radionuclides in the 1950s. Despite a shared background, however, societal events, often in the form of legislation, have affected the development path for risk assessment for human health, producing dissimilarities between these risk assessments and those for nuclear facilities. An important difference is the regulator's interest in accounting for uncertainty.
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  • 6
    ISSN: 1539-6924
    Keywords: risk perception ; CRESP ; trust ; DOE Savannah River site ; risk assessment ; stakeholder ; economic dependence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Environmental managers are increasingly charged with involving the public in the development and modification of policies regarding risks to human health and the environment. Involving the public in environmental decision making first requires a broad understanding of how and why the public perceives various risks. The Savannah River Stakeholder Study was conducted with the purpose of investigating individual, economic, and social characteristics of risk perceptions among those living near the Savannah River Nuclear Weapons Site. A number of factors were found to impact risk perceptions among those living near the site. One's estimated proximity to the site and relative river location surfaced as strong determinants of risk perceptions among SRS residents. Additionally, living in a quality neighborhood and demonstrating a willingness to accept health risks for economic gain strongly abated heightened risk perceptions.
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  • 7
    ISSN: 1539-6924
    Keywords: risk assessment ; uncertainty ; formaldehyde ; decision analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A call for risk assessment approaches that better characterize and quantify uncertainty has been made by the scientific and regulatory community. This paper responds to that call by demonstrating a distributional approach that draws upon human data to derive potency estimates and to identify and quantify important sources of uncertainty. The approach is rooted in the science of decision analysis and employs an influence diagram, a decision tree, probabilistic weights, and a distribution of point estimates of carcinogenic potency. Its results estimate the likelihood of different carcinogenic risks (potencies) for a chemical under a specific scenario. For this exercise, human data on formaldehyde were employed to demonstrate the approach. Sensitivity analyses were performed to determine the relative impact of specific levels and alternatives on the potency distribution. The resulting potency estimates are compared with the results of an exercise using animal data on formaldehyde. The paper demonstrates that distributional risk assessment is readily adapted to situations in which epidemiologic data serve as the basis for potency estimates. Strengths and weaknesses of the distributional approach are discussed. Areas for further application and research are recommended.
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  • 8
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    Risk analysis 19 (1999), S. 1157-1171 
    ISSN: 1539-6924
    Keywords: risk assessment ; transportation risk ; diesel exhaust ; fugitive dust ; vehicle emissions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract When the transportation risk posed by shipments of hazardous chemical and radioactive materials is being assessed, it is necessary to evaluate the risks associated with both vehicle emissions and cargo-related risks. Diesel exhaust and fugitive dust emissions from vehicles transporting hazardous shipments lead to increased air pollution, which increases the risk of latent fatalities in the affected population along the transport route. The estimated risk from these vehicle-related sources can often be as large or larger than the estimated risk associated with the material being transported. In this paper, data from the U.S. Environmental Protection Agency's Motor Vehicle-Related Air Toxics Study are first used to develop latent cancer fatality estimates per kilometer of travel in rural and urban areas for all diesel truck classes. These unit risk factors are based on studies investigating the carcinogenic nature of diesel exhaust. With the same methodology, the current per-kilometer latent fatality risk factor used in transportation risk assessments for heavy diesel trucks in urban areas is revised and the analysis expanded to provide risk factors for rural areas and all diesel truck classes. These latter fatality estimates may include, but are not limited to, cancer fatalities and are based primarily on the most recent epidemiological data available on mortality rates associated with ambient air PM-10 concentrations.
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  • 9
    ISSN: 1539-6924
    Keywords: municipal waste incineration ; risk assessment ; Monte-Carlo simulation ; time activity patterns
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract During the modernization of the municipal waste incinerator (MWI, maximum capacity of 180,000 tons per year) of Metropolitan Grenoble (405,000 inhabitants), in France, a risk assessment was conducted, based on four tracer pollutants: two volatile organic compounds (benzene and 1, 1, 1 trichloroethane) and two heavy metals (nickel and cadmium, measured in particles). A Gaussian plume dispersion model, applied to maximum emissions measured at the MWI stacks, was used to estimate the distribution of these pollutants in the atmosphere throughout the metropolitan area. A random sample telephone survey (570 subjects) gathered data on time-activity patterns, according to demographic characteristics of the population. Life-long exposure was assessed as a time-weighted average of ambient air concentrations. Inhalation alone was considered because, in the Grenoble urban setting, other routes of exposure are not likely. A Monte Carlo simulation was used to describe probability distributions of exposures and risks. The median of the life-long personal exposures distribution to MWI benzene was 3.2·10−5 μg/m3 (20th and 80th percentiles = 1.5·10−5 and 6.5·10−5 μg/m3), yielding a 2.6·10−10 carcinogenic risk (1.2·10−10–5.4·10−10). For nickel, the corresponding life-time exposure and cancer risk were 1.8·10−4 μg/m3 (0.9.10−4 – 3.6·10−4 μg/m3) and 8.6·10−8 (4.3·10−8–17.3·10−8); for cadmium they were respectively 8.3·10−6 μg/m3 (4.0·10−6–17.6·10−6) and 1.5·10−8 (7.2·10−9–3.1·10−8). Inhalation exposure to cadmium emitted by the MWI represented less than 1% of the WHO Air Quality Guideline (5 ng/m3), while there was a margin of exposure of more than 109 between the NOAEL (150 ppm) and exposure estimates to trichloroethane. Neither dioxins nor mercury, a volatile metal, were measured. This could lessen the attributable life-long risks estimated. The minute (VOCs and cadmium) to moderate (nickel) exposure and risk estimates are in accord with other studies on modern MWIs meeting recent emission regulations, however.
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  • 10
    ISSN: 1539-6924
    Keywords: MeHg ; pharmacokinetics ; PBPK model ; variability ; risk assessment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract An analysis of the uncertainty in guidelines for the ingestion of methylmercury (MeHg) due to human pharmacokinetic variability was conducted using a physiologically based pharmacokinetic (PBPK) model that describes MeHg kinetics in the pregnant human and fetus. Two alternative derivations of an ingestion guideline for MeHg were considered: the U.S. Environmental Protection Agency reference dose (RfD) of 0.1 μg/kg/day derived from studies of an Iraqi grain poisoning episode, and the Agency for Toxic Substances and Disease Registry chronic oral minimal risk level (MRL) of 0.5 μg/kg/day based on studies of a fish-eating population in the Seychelles Islands. Calculation of an ingestion guideline for MeHg from either of these epidemiological studies requires calculation of a dose conversion factor (DCF) relating a hair mercury concentration to a chronic MeHg ingestion rate. To evaluate the uncertainty in this DCF across the population of U.S. women of child-bearing age, Monte Carlo analyses were performed in which distributions for each of the parameters in the PBPK model were randomly sampled 1000 times. The 1st and 5th percentiles of the resulting distribution of DCFs were a factor of 1.8 and 1.5 below the median, respectively. This estimate of variability is consistent with, but somewhat less than, previous analyses performed with empirical, one-compartment pharmacokinetic models. The use of a consistent factor in both guidelines of 1.5 for pharmacokinetic variability in the DCF, and keeping all other aspects of the derivations unchanged, would result in an RfD of 0.2 μg/kg/day and an MRL of 0.3 μg/kg/day.
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  • 11
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    Risk analysis 19 (1999), S. 577-584 
    ISSN: 1539-6924
    Keywords: risk assessment ; exposure point concentration ; bootstrapping ; gamma distribution ; lognormal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The U.S. Environmental Protection Agency (EPA) recommends the use of the one-sided 95% upper confidence limit of the arithmetic mean based on either a normal or lognormal distribution for the contaminant (or exposure point) concentration term in the Superfund risk assessment process. When the data are not normal or lognormal this recommended approach may overestimate the exposure point concentration (EPC) and may lead to unecessary cleanup at a hazardous waste site. The EPA concentration term only seems to perform like alternative EPC methods when the data are well fit by a lognormal distribution. Several alternative methods for calculating the EPC are investigated and compared using soil data collected from three hazardous waste sites in Montana, Utah, and Colorado. For data sets that are well fit by a lognormal distribution, values for the Chebychev inequality or the EPA concentration term may be appropriate EPCs. For data sets where the soil concentration data are well fit by gamma distributions, Wong's method may be used for calculating EPCs. The studentized bootstrap-t and Hall's bootstrap-t transformation are recommended for EPC calculation when all distribution fits are poor. If a data set is well fit by a distribution, parametric bootstrap may provide a suitable EPC.
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  • 12
    ISSN: 1539-6924
    Keywords: regulation ; radioactive waste ; performance assessment ; risk assessment ; regulatory assessment ; bias evaluation ; international collaboration ; underground disposal ; quantitative risk analysis ; public debate ; decision process
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Much has been written about the development and application of quantitative methods for estimating under uncertainty the long-term radiological performance of underground disposal of radioactive wastes. Until recently, interest has been focused almost entirely on the technical challenges regardless of the role of the organization responsible for these analyses. Now the dialogue between regulators, the repository developer or operator, and other interested parties in the decision-making process receives increasing attention, especially in view of some current difficulties in obtaining approvals to construct or operate deep facilities for intermediate or high-level wastes. Consequently, it is timely to consider the options for regulators' review and evaluation of safety submissions, at the various stages in the site selection to repository closure process, and to consider, especially, the role for performance assessment (PA) within the programs of a regulator both before and after delivery of such a submission. The origins and broad character of present regulations in the European Union (EU) and in the OECD countries are outlined and some regulatory PA reviewed. The issues raised are discussed, especially in regard to the interpretation of regulations, the dangers from the desire for simplicity in argument, the use of regulatory PA to review and challenge the PA in the safety case, and the effects of the relationship between proponent and regulator. Finally, a very limited analysis of the role of PA in public hearings is outlined and recommendations are made, together with proposals for improving the mechanisms for international collaboration on technical issues of regulatory concern.
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  • 13
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    Risk analysis 18 (1998), S. 679-688 
    ISSN: 1539-6924
    Keywords: Air quality ; benchmarking ; best available control technology ; contaminant exposure ; risk assessment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Although occupational exposure limits are sought to establish health-based standards, they do not always give a sufficient basis for planning an indoor air climate that is good and comfortable for the occupants in industrial work rooms. This paper considers methodologies by which the desired level, i.e., target level, of air quality in industrial settings can be defined, taking into account feasibility issues. Risk assessment based on health criteria is compared with risk-assessment based on “Best Available Technology” (BAT). Because health-based risk estimates at low concentration regions are rather inaccurate, the technology-based approach is emphasized. The technological approach is based on information on the prevailing concentrations in industrial work environments and the benchmark air quality attained with the best achievable technology. The prevailing contaminant concentrations are obtained from a contaminant exposure databank, and the benchmark air quality by field measurements in industrial work rooms equipped with advanced ventilation and production technology. As an example, the target level assessment has been applied to formaldehyde, total inorganic dust and hexavalent chromium, which are common contaminants in work room air.
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  • 14
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    Risk analysis 19 (1999), S. 23-32 
    ISSN: 1539-6924
    Keywords: Software failures ; software hazard analysis ; safety-critical systems ; risk assessment ; context
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract As the use of digital computers for instrumentation and control of safety-critical systems has increased, there has been a growing debate over the issue of whether probabilistic risk assessment techniques can be applied to these systems. This debate has centered on the issue of whether software failures can be modeled probabilistically. This paper describes a “context-based” approach to software risk assessment that explicitly recognizes the fact that the behavior of software is not probabilistic. The source of the perceived uncertainty in its behavior results from both the input to the software as well as the application and environment in which the software is operating. Failures occur as the result of encountering some context for which the software was not properly designed, as opposed to the software simply failing “randomly.” The paper elaborates on the concept of “error-forcing context” as it applies to software. It also illustrates a methodology which utilizes event trees, fault trees, and the Dynamic Flowgraph Methodology (DFM) to identify “error-forcing contexts” for software in the form of fault tree prime implicants.
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  • 15
    ISSN: 1539-6924
    Keywords: Benchmark ; mercury ; risk assessment ; epidemiology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract This paper presents benchmark (BMD) calculations and additional regression analyses of data from a study in which scores from 26 scholastic and psychological tests administered to 237 6- and 7-year-old New Zealand children were correlated with the mercury concentration in their mothers' hair during pregnancy. The original analyses of five test scores found an association between high prenatal mercury exposure and decreased test performance, using category variables for mercury exposure. Our regression analyses, which utilized the actual hair mercury level, did not find significant associations between mercury and children's test scores. However, this finding was highly influenced by a single child whose mother's mercury hair level (86 mg/kg) was more than four times that of any other mother. When that child was omitted, results were more indicative of a mercury effect and scores on six tests were significantly associated with the mothers' hair mercury level. BMDs calculated from five tests ranged from 32 to 73 mg/kg hair mercury, and corresponding BMDLs (95% lower limits on BMDs) ranged from 17 to 24 mg/kg. When the child with the highest mercury level was omitted, BMDs ranged from 13 to 21 mg/kg, and corresponding BMDLs ranged from 7.4 to 10 mg/kg.
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  • 16
    ISSN: 1539-6924
    Keywords: Remediation ; stakeholders ; deliberation ; risk assessment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The National Research Council has recommended the use of an analytic/deliberative decision-making process in environmental restoration decisions that involve multiple stakeholders. This work investigates the use of the results of risk assessment and multiattribute utility analysis (the “analysis”) in guiding the deliberation. These results include the ranking of proposed remedial action alternatives according to each stakeholder's preferences, as well as the identification of the major reasons for these rankings. The stakeholder preferences are over a number of performance measures that include the traditional risk assessment metrics, e.g., individual worker risk, as well as programmatic, cultural, and cost-related impacts. Based on these results, a number of proposals are prepared for consideration by the stakeholders during the deliberation. These proposals are the starting point for the formulation of actual recommendations by the group. In our case study, these recommendations included new remedial action alternatives that were created by the stakeholders after an extensive discussion of the detailed analytical results.
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  • 17
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    Risk analysis 19 (1999), S. 327-334 
    ISSN: 1539-6924
    Keywords: Biological introductions ; binucleate Rhizoctonia ; biocontrol ; risk assessment ; seedlings ; susceptibility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract This article describes an application of a method for assessing risks associated with the introduction of an organism into a new environment. The test organism was a binucleate Rhizoctonia fungal isolate that has potential for commercial development as a biological control agent for damping-off diseases in bedding plants. A test sample of host plant species was selected using the centrifugal phylogenetic host range principles, but with an emphasis on economic species. The effect of the fungus on the plant was measured for each species and expressed on a logarithmic scale. The effects on weights of shoots and roots per container were not normally distributed, nor were the effects on the number of plants standing (those which survived). Statements about the effect on the number standing and the shoot weight per container involved using the observed (empirical) distribution. This is illustrated with an example. Problems were encountered in defining the population of species at risk, and in deciding how this population should be formally sampled. The limitations of the method are discussed.
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  • 18
    ISSN: 1539-6924
    Keywords: dose-response ; models ; food-borne ; pathogens ; risk assessment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Food-related illness in the United States is estimated to affect over six million people per year and cost the economy several billion dollars. These illnesses and costs could be reduced if minimum infectious doses were established and used as the basis of regulations and monitoring. However, standard methodologies for dose-response assessment are not yet formulated for microbial risk assessment. The objective of this study was to compare dose-response models for food-borne pathogens and determine which models were most appropriate for a range of pathogens. The statistical models proposed in the literature and chosen for comparison purposes were log-normal, log-logistic, exponential, β-Poisson and Weibull-Gamma. These were fit to four data sets also taken from published literature, Shigella flexneri, Shigella dysenteriae,Campylobacter jejuni, and Salmonella typhosa, using the method of maximum likelihood. The Weibull-gamma, the only model with three parameters, was also the only model capable of fitting all the data sets examined using the maximum likelihood estimation for comparisons. Infectious doses were also calculated using each model. Within any given data set, the infectious dose estimated to affect one percent of the population ranged from one order of magnitude to as much as nine orders of magnitude, illustrating the differences in extrapolation of the dose response models. More data are needed to compare models and examine extrapolation from high to low doses for food-borne pathogens.
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  • 19
    ISSN: 1539-6924
    Keywords: ethylene oxide ; risk assessment ; epidemiology ; cancer guidelines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Ethylene oxide (EO) research has significantly increased since the 1980s, when regulatory risk assessments were last completed on the basis of the animal cancer chronic bioassays. In tandem with the new scientific understanding, there have been evolutionary changes in regulatory risk assessment guidelines, that encourage flexibility and greater use of scientific information. The results of an updated meta-analysis of the findings from 10 unique EO study cohorts from five countries, including nearly 33,000 workers, and over 800 cancers are presented, indicating that EO does not cause increased risk of cancers overall or of brain, stomach or pancreatic cancers. The findings for leukemia and non-Hodgkin's lymphoma (NHL) are inconclusive. Two studies with the requisite attributes of size, individual exposure estimates and follow up are the basis for dose-response modeling and added lifetime risk predictions under environmental and occupational exposure scenarios and a variety of plausible alternative assumptions. A point of departure analysis, with various margins of exposure, is also illustrated using human data. The two datasets produce remarkably similar leukemia added risk predictions, orders of magnitude lower than prior animal-based predictions under conservative, default assumptions, with risks on the order of 1 × 10−6 or lower for exposures in the low ppb range. Inconsistent results for “lymphoid” tumors, a non-standard grouping using histologic information from death certificates, are discussed. This assessment demonstrates the applicability of the current risk assessment paradigm to epidemiological data.
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  • 20
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    Risk analysis 19 (1999), S. 1223-1234 
    ISSN: 1539-6924
    Keywords: risk assessment ; standard-setting ; carcinogens ; OSHA ; ACGIH
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract For carcinogens, this paper provides a quantitative examination of the roles of potency and weight-of-evidence (WOE) in setting permissible exposure limits (PELs) at the U.S. Occupational Safety and Health Administration (OSHA) and threshold limit values (TLVs) at the private American Conference of Governmental Industrial Hygienists (ACGIH). On normative grounds, both of these factors should influence choices about the acceptable level of exposures. Our major objective is to examine whether and in what ways these factors have been considered by these organizations. A lesser objective is to identify outliers, which might be candidates for further regulatory scrutiny. Our sample (N=48) includes chemicals for which EPA has estimated a unit risk as a measure of carcinogenic potency and for which OSHA or the ACGIH has a PEL or TLV. Different assessments of the strength of the evidence of carcinogenicity were obtained from EPA, ACGIH, and the International Agency for Research on Cancer. We found that potency alone explains 49% of the variation in PELs and 62% of the variation in TLVs. For the ACGIH, WOE plays a much smaller role than potency. TLVs set by the ACGIH since 1989 appear to be stricter than earlier TLVs. We suggest that this change represents evidence that the ACGIH had responded to criticisms leveled at it in the late 1980s for failing to adopt sufficiently protective standards. The models developed here identify 2-nitropropane, ethylene dibromide, and chromium as having OSHA PELs significantly higher than predicted on the basis of potency and WOE.
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  • 21
    ISSN: 1539-6924
    Keywords: Extreme events ; risk assessment ; risk management ; extreme value theory ; judgmental distributions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract In this paper, we review methods for assessing and managing the risk of extreme events, where “extreme events” are defined to be rare, severe, and outside the normal range of experience of the system in question. First, we discuss several systematic approaches for identifying possible extreme events. We then discuss some issues related to risk assessment of extreme events, including what type of output is needed (e.g., a single probability vs. a probability distribution), and alternatives to the probabilistic approach. Next, we present a number of probabilistic methods. These include: guidelines for eliciting informative probability distributions from experts; maximum entropy distributions; extreme value theory; other approaches for constructing prior distributions (such as reference or noninformative priors); the use of modeling and decomposition to estimate the probability (or distribution) of interest; and bounding methods. Finally, we briefly discuss several approaches for managing the risk of extreme events, and conclude with recommendations and directions for future research.
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  • 22
    ISSN: 1539-6924
    Keywords: Market response ; risk assessment ; airplane accidents ; airline industry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The risk of catastrophic failures, for example in the aviation and aerospace industries, can be approached from different angles (e.g., statistics when they exist, or a detailed probabilistic analysis of the system). Each new accident carries information that has already been included in the experience base or constitutes new evidence that can be used to update a previous assessment of the risk. In this paper, we take a different approach and consider the risk and the updating from the investor's point of view. Based on the market response to past airplane accidents, we examine which ones have created a “surprise response” and which ones are considered part of the risk of the airline business as previously assessed. To do so, we quantify the magnitude and the timing of the observed market response to catastrophic accidents, and we compare it to an estimate of the response that would be expected based on the true actual cost of the accident including direct and indirect costs (“full-cost information” response). First, we develop a method based on stock market data to measure the actual market response to an accident and we construct an estimate of the “full-cost information” response to such an event. We then compare the two figures for the immediate and the long-term response of the market for the affected firm, as well as for the whole industry group to which the firm belongs. As an illustration, we analyze a sample of ten fatal accidents experienced by major US domestic airlines during the last seven years. In four cases, we observed an abnormal market response. In these instances, it seems that the shareholders may have updated their estimates of the probability of a future accident in the affected airlines or more generally of the firm's future business prospects. This market reaction is not always easy to explain much less to anticipate, a fact which management should bear in mind when planning a firm's response to such an event.
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  • 23
    ISSN: 1539-6924
    Keywords: Uncertainty ; variability ; risk assessment ; risk management ; ozone ; clean air act ; social policy ; analysis of benefits and costs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract This paper is a challenge from a pair of lifelong technical specialists in risk assessment for the risk-management community to better define social decision criteria for risk acceptance vs. risk control in relation to the issues of variability and uncertainty. To stimulate discussion, we offer a variety of “straw man” proposals about where we think variability and uncertainty are likely to matter for different types of social policy considerations in the context of a few different kinds of decisions. In particular, we draw on recent presentations of uncertainty and variability data that have been offered by EPA in the context of the consideration of revised ambient air quality standards under the Clean Air Act.
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  • 24
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    Risk analysis 19 (1999), S. 135-152 
    ISSN: 1539-6924
    Keywords: Probability ; uncertainty ; data ; risk assessment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Risk assessors attempting to use probabilistic approaches to describe uncertainty often find themselves in a data-sparse situation: available data are only partially relevant to the parameter of interest, so one needs to adjust empirical distributions, use explicit judgmental distributions, or collect new data. In determining whether or not to collect additional data, whether by measurement or by elicitation of experts, it is useful to consider the expected value of the additional information. The expected value of information depends on the prior distribution used to represent current information; if the prior distribution is too narrow, in many risk-analytic cases the calculated expected value of information will be biased downward. The well-documented tendency toward overconfidence, including the neglect of potential surprise, suggests this bias may be substantial. We examine the expected value of information, including the role of surprise, test for bias in estimating the expected value of information, and suggest procedures to guard against overconfidence and underestimation of the expected value of information when developing prior distributions and when combining distributions obtained from multiple experts. The methods are illustrated with applications to potential carcinogens in food, commercial energy demand, and global climate change.
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  • 25
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    European journal of nutrition 34 (1995), S. 113-117 
    ISSN: 1436-6215
    Keywords: Blei ; Cadmium ; Quecksilber ; Gewürze ; Gewürzzubereitungen ; Wurstwaren ; Lead ; cadmium ; mercury ; spices ; condiments ; meat products
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Summary The lead and cadmium contents of 50 spices and 19 condiments were investigated by means of flameless atomic absorption spectrophotometry. Mercury contents were determined by cold vapor atomic absorption method including amalgamation. The mean concentrations of lead, cadmium, and mercury were 0.470 mg/kg, 0.080 mg/kg, and 0.005 mg/kg, respectively. By using the detected levels of these three heavy metals in model calculations only a small carry-over of lead, cadmium, and mercury in meat products by spices and condiments can be assumed.
    Notes: Zusammenfassung 50 Gewürze und 19 Gewürzzubereitungen wurden mittels flammenloser Atomabsorptionsspektrometrie auf ihren Blei- und Cadmiumgehalt sowie mittels Kaltdampftechnik und nachfolgender Amalgamierung auf ihren Quecksilbergehalt untersucht. Im Mittel wurden hierbei 0,470 mg Blei, 0,080 mg Cadmium und 0,005 mg Quecksilber pro kg Würzmittel gefunden. Anhand von Modellrechnungen wurde ein nur geringer Blei-, Cadmium- und Quecksilbereintrag über Würzmittel in die Wurstsorten Fleischwurst, Leberwurst und Mettwurst aufgezeigt.
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  • 26
    ISSN: 1439-0361
    Keywords: Biocides ; organochlorines ; mercury ; pollution ; river Rhine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung 1994/95 durchgeführte Vergleichsuntersuchungen zur Belastung von Binnenland- und Wattenmeerbrütern des Austernfischers mit den Bioziden DDT, DDE und HCH sowie den Industriechemikalien PCB, HCB und Hg ergaben in Austernfischer-Eiern vom Unteren Niederrhein signifikant höhere Konzentrationen chlororganischer Verbindungen als in Eiern der Wattenmeerinseln Griend (NL) und Mellum (D). Nur Hg wurde in niederrheinischen Eiern in hoch signifikant geringerer Konzentration gefunden als in Eiern von Brutvögel des Wattenmeeres. Austernfischer-Eier von Griend waren bezüglich der meisten analysierten Parameter geringer belastet als Eier von Mellum (Ausnahmen: pp'DDT, Σ PCB). Von den untersuchten Umweltchemikalien war die PCB-Konzentration in allen drei Untersuchungsgebieten am höchsten. Die hohe PCB-Kontamination am Unteren Niederrhein spiegelt die auch heute noch erhebliche Belastung des Flusses mit „Altlasten” wider. Weder die Konzentration der untersuchten Industriechemikalien noch die der Biozide dürften von embryotoxischer Wirkung gewesen sein.
    Notes: Summary Due to the international importance of the Wadden Sea for waders and waterfowl a long-term programme to monitor contamination of birds breeding in the Wadden Sea has been established in the early 1980s. One of the species selected is the Oystercatcher. Comparatively little is known about contamination of birds breeding inland. Therefore, we collected eight eggs of Oystercatchers breeding at the Lower Rhine (district of Kleve) and analysed their contamination with biocides (DDT, DDE, HCH) and industrial chemicals (PCB, HCB, Hg) in comparison to birds breeding on the Wadden Sea islands of Griend (NL) and Mellum (D), where ten eggs were collected in 1994/95. We found distinctive differences between inland and Wadden Sea breeding Oystercatchers. Eggs from the Lower Rhine had significantly higher residues of all organochlorines, whereas concentration of mercury was significantly lower than in those from birds breeding on the Wadden Sea islands. In general, eggs collected on Griend held lower concentrations than those collected on Mellum island, except pp'-DDT and Σ PCB. The high PCB contamination in Ostercatcher eggs from the Lower Rhine nowadays reflects the extreme pollution in the past. However, concentrations of the parameters studied obviously had no embryotoxic effects in Oystercatchers.
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  • 27
    ISSN: 1570-7458
    Keywords: copper ; mercury ; chromatin supraorganization ; survival ; Triatoma infestans ; Hemiptera
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The nuclear phenotypes and survival of the hemipteran,Triatoma infestans (Hemiptera, Reduviidae), were studied in specimens treated with copper sulfate and methylmercury. The objective was to determine whether changes in chromatin supraorganization and insect survival similar to those promoted by other stressing agents could also be induced by heavy metals. At the concentrations used, copper sulfate and methylmercury were toxic to the cells, mainly inducing nuclear degenrration in the Malpighian tubules and being lethal to a large part of the insect population. Although some individual resistance was found, especially in fasted specimens, heavy metals were found to be much more lethal than was, for instance, a thermal shock at 0°C for 12 h. The nuclear phenotypes detected after heavy metal treatment were similar to those reported under other stressing conditions. However, the frequency at which nuclei exhibited aspects of heterochromatin unraveling was much higher than that found in fasted and thermal-shocked specimens, and was independent of the heavy metal type used. If this phenotype represents an attempt to improve opportunities for extensive cell and insect survival, it was not sufficiently effective. In 5th instar nymphs, the effect of CuSO4 on chromatin supraorganization was detected at early steps of spermatogenesis but not in the cells which were at late spermiogenesis when the metal was administered. This is probably due to changes in nuclear protein composition and to the tightly packed state of the DNA-protein complexes occurring at spermiogenesis, which may protect chromatin from damages. However, when CuSO4 was supplied to 4th instar nymphs, it slowed down the spermiogenesis process, possibly due to several factors including Cu2+ binding to DNA phosphates.
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  • 28
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    Fire technology 32 (1996), S. 297-307 
    ISSN: 1572-8099
    Keywords: fire ; safety ; design ; regulations ; performance ; guidelines ; risk assessment ; evaluation ; criteria ; technology transfer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying
    Notes: Abstract Australia is quickly moving toward adopting performance-based regulations for building fire safety. This approach offers owners and designers more flexibility, greater opportunity for innovation, and more cost-effective construction. To help introduce a performance approach, the Fire Code Reform Centre has developedFire Engineering Guidelines, which document an agreed methodology for performance-based design and draws on earlier Australian research and similar developments in a number of countries. The guidelines are the first step in a broader research program to develop a full risk assessment methodology as the basis for fire safety design in Australia.
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  • 29
    ISSN: 1572-8862
    Keywords: Platinum ; mercury ; ruthenium ; heteronuclear ; cluster ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Addition of a THF solution prepared by stirring [CpRu(CO)2]2 over Na/Hg amalgam to a solution of the triplatinum cluster [Pt3(dppm)3(CO)][PF6]2 (1) in THF gives the heteronuclear cluster [Pt3(dppm)3{(μ4-Hg)–RuCp(CO)2}2] [PF6]2 (2) in 40% yield following chromatography. A single crystal X-ray study of 2 reveals structural parameters for the Pt3Hg2 molecular core that are consistent with those of other structurally characterized complexes of this type. 1H, 13C, and 31P NMR spectra of this complex indicate that the structure observed in the solid state is retained in solution.
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  • 30
    ISSN: 1572-8773
    Keywords: mercury ; Na-K-ATPase ; rat liver ; signal transduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Specific binding of Hg to ouabain-sensitive Na-K-ATPase of rat liver plasma membrane was demonstrated with a K of 2.64¥10 and B of 1.6nmole mg protein. The binding of mercury to the enzyme also causes significant inhibition of the enzyme, which is greater than its ouabain sensitivity. In the cytosol Hg binding to reduced glutathione (GSH) is stimulated by GSH-S-transferase (GST), the activity of which was found to be significantly enhanced by 15mM Na and 10mM Hg. It is proposed that the transport of Hg2 inside the cell takes place by increased dissociation of Hg from the membrane due to greater avidity of Hg towards cytosolar GSH binding. The GSH-Hg complex enters the nucleus where it dissociates to bind the metal response element (MRE) of the metallothionein (MT) gene to induce MT transcription.
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  • 31
    ISSN: 1572-8773
    Keywords: lead ; mercury ; metals ; nickel ; radiation effects ; selenium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Effects of Pb2+, Ni2+, Hg2+ and Se4+ on cultured human glioma U-343MG cells were investigated considering uptake, toxicity and, in combination with radiation, clonogenic cell survival. The cells were exposed to 0-100 μm of the metals for a week before the evaluation. The tests showed a tendency to toxicity with 10 μm nickel although not significant (P 〉 0.05). Selenium, lead and mercury exerted a significant toxicity (P 〈 0.05) at 2.5 μm, 10 μm and 1 μm, respectively. To challenge the clonogenic cell survival capacity, the cells were irradiated with60Co photons after being exposed to the highest nontoxic concentration of the different metals. The clonogenic cell survival tests, after irradiation, showed no significant change if the cells were exposed to 5 μm nickel, 0.5 μm selenium or 5 μm lead compared with those not exposed. Mercury, 0.1 μm, gave a relative reduction in survival compared with only irradiated cells of 58 ± 17%. Thus, only mercury affected the radiation-induced damage and/or repair. When exposed to the highest nontoxic concentrations of the different metals, the cultures did not display a significant uptake ratio (metal concentration ratio of exposed cells to control cells) of nickel (3.1 ± 3.3), only a small uptake ratio of selenium (4.0 ± 0.4), while there was a large uptake ratio of both lead (2.6 ± 1.7) x 102 and mercury (1.5 ± 0.2) x 101. The results indicated that nickel was neither especially toxic nor influenced the clonogenic cell survival after irradiation. Mercury was more toxic and also influenced the radiation sensitivity. Lead was taken up strongly but did not influence the radiation sensitivity. Selenium accumulated but gave no detectable effect on the radiation sensitivity.
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  • 32
    ISSN: 1572-8773
    Keywords: 3β-HSD ; fish oocyte ; mercury ; Na-K-ATPase ; steroidogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Both in vitro and in vivo HgCl treatment demonstrated a remarkably high rate of progesterone synthesis accompanied by a low rate of conversion to 17β-estradiol in the oocyte of Channa punctatus. On depuration, however, there was a reversal of the steroidogenic scenario with a low progesterone and high estradiol level. The accumulation of progesterone was positively correlated with the significant increase in 3β-hydroxysteroid dehydrogenase activity in the Hg-treated fish. Thus, it was clear that at the early stage of intoxication Hg does play a role in the induction of 3β-hydroxysteroid dehydrogenase in the oocyte of fish at the spawning stage. The induction of this enzyme was found to be mediated by specific binding of Hg to the plasma membrane Na-K-ATPase (B: 14 nmoles mg protein; K 1.14 x 108 moles) and increase in the specific messenger RNA translating 3β-hydroxysteroid dehydrogenase. It is concluded that inorganic mercury is able to initiate translatable messenger RNA synthesis in fish oocyte at a low degree of intoxication.
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  • 33
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    BioMetals 10 (1997), S. 357-361 
    ISSN: 1572-8773
    Keywords: copper ; exposure ; mercury ; smoking ; zinc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The excretion of mercury, copper and zinc in urine, and mercury in whole blood andplasma, was determined in 40 chloralkali workers exposed to mercury vapour and 40age-matched referents. The Hg concentrations in whole blood, plasma and urine werehigher in the exposed group (35 nmol l, 30 nmol l,and 11.5 nmol mmol creatinine, respectively) in comparison with thereference group (15 nmol l, 6.3 nmol l, and 1.8nmol mmol creatinine, respectively). The urinary copper excretionwas similar in the two groups, while U-Zn excretion was significantly higher (P = 0.04)in the exposed group, median 0.83 mmol mmol creatinine versus 0.76mnmol mmol creatinine in the reference group. In a subgroup of exposedworkers with current U-Hg above 11.5 nmol lmmolcreatinine (20 mg g creatinine) the medianU-Zn was 1.1 mmol mmol creatinine. In both groups smokers had highU-Zn levels than non smokers. When both U-Hg and smoking were taken into account in alinear regression model, there was a significant association between U-Hg and U-Zn inthe combined group of exposed and referents (P = 0.002). This study indicates thatmercury exposure in humans, as in animals, causes increased urinary excretion of zinc.The mechanisms may be induced synthesis of metallothionein in the kidneys, displacementof Zn from preexisting metallothionein by Hg, or a decreased reabsorption of zinc in thekidneys owing to a slight tubular dysfunction.
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  • 34
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    BioMetals 11 (1998), S. 139-143 
    ISSN: 1572-8773
    Keywords: feathers ; pheasant ; mercury ; muscles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Mercury concentrations were determined in muscles and feathers of 58 cock pheasants. Birds were collected from seven different polluted sites in southern Poland in 1987. The mercury concentrations in the muscle ranged from 0.010 to 0.026 mug g dry mass. The significantly highest values were found in muscle samples from Przylasek and Przemysl. The levels found in the flight feathers were higher than in breast feathers. Average concentrations in flight feathers ranged from 0.050 mug g (Przemysl) to 0.240 mug g dry mass (Przylasek). © Rapid Science 1998
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  • 35
    ISSN: 1572-8773
    Keywords: capsule secondary structure ; exopolysaccharide ; bacterial cell surface ; copper ; mercury ; ytterbium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Escherichia coli K1 secretes a homopolymer capsular polysaccharide (CPS) consisting of alpha 2,8 linked N-acetylneuraminic acid (poly α2,8NeuNAc). Typically poly α2,8NeuNAc is arranged in low and high order alpha helices with carboxyl and hydroxyl groups extending from the helices. Several properties of CPS such as antigenicity and metal binding can be influenced by its structural conformation. We examined the influences of metal ions and temperature on the secondary structure of polyαa2,8NeuNAc. Conformation alteration was detected by ultraviolet (UV) spectroscopy and circular dichroism (CD). The majority of metal ions tested had no detectable influence on poly a2,8NeuNAc structure. In contrast, Yb3+., Hg2+, and Cu2+ ions greatly altered the UV and CD spectra, which suggests that these ions had disrupted the alpha helical structure of poly α2,8NeuNAc. These changes were influenced by the metal ion concentration. When poly α2,8NeuNAc was incubated at temperatures ranging from 20 - 60°C, alterations in its UV absorption spectra were also seen. The most significant change occurred between 35 and 40°C. In summary, this study suggests that the higher order structure and function of bacterial CPS may be influenced by environmental factors
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  • 36
    ISSN: 1572-8773
    Keywords: mercury ; urine ; feces ; gastrointestinal absorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The effects of long-term daily intake of mercury on its urinary and fecal excretion, whole-body retention, and blood concentration in male rats were observed. The animals were exposed to mercuric chloride labeled with 203Hg via drinking water for 8 weeks (5, 50 and 500 μ m Hg). 203Hg in urine, feces and blood was quantified. The blood mercury concentration did not keep a linear relationship with the increasing dose. The percentage of the total amount of mercury intake which is excreted by the fecal route in rats exposed to 500 μ m Hg was significantly lower than in those exposed to 5 and 50 μ m. The daily dose percentage of mercury excreted in urine increased with dose size. The results show that the absorption fraction of mercury through the gastrointestinal tract (30–40%) was higher than values previously reported.
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  • 37
    ISSN: 1572-8773
    Keywords: mercury ; kidney ; metallothionein ; oral exposure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The effects of long-term daily intake of low and high levels of mercury on its organ distribution and binding to renal metallothionein (MT) in male rats were studied. The animals were exposed to mercuric chloride labelled with203Hg via drinking water for 8 weeks (5, 50 and 500μ m Hg). The greatest concentration of mercury was found in the kidneys. Similar levels of radioactivity in the buccal cavity and oesophagus were also observed by whole-body autoradiography. In the kidneys, the mercury was accumulated in the outer stripe of the outer zone of the medulla and, to a minor degree, in the renal cortex. Almost 50% the total renal mercury was associated to MT. The binding capacity of the renal MT for mercury tends to saturate with increasing doses, thus this means that the capacity of the kidneys to accumulate mercury is limited.
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  • 38
    ISSN: 1572-9435
    Keywords: grade crossings ; level crossings ; railway safety ; risk assessment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying
    Notes: Abstract This paper describes the application of probabilistic risk assessment techniques to level crossing safety on JR East, the largest of the six private railroads in Japan. The risk of a level crossing accident was defined as the product of the accident rate and the expected consequences per accident. Rail traffic volume, road traffic volume, visibility of the crossing from the road, road gradient, width of the crossing and the type of safety devices at the crossing were shown to influence the accident rate and the collective risk. The mean accident rate at all crossings was 0.74 per million trains. The accident rate was 0.59 per million trains at crossings equipped with barriers, 1.25 at crossings equipped with warning bells and 0.76 at pedestrian crossings. Crossings equipped with obstacle detectors had a lower accident rate (0.12 per million trains) than crossings without detectors (0.43 per million trains). Crossings with visibility less than 20 m had a 50% higher mean accident rate than crossings with visibility greater than 20 m. As the number of tracks increased, the accident rate monotonically increased due to the increased accident exposure. Risk assessment techniques were applied to determine the efficacy of the various level crossing safety devices. In addition to upgrading the safety of crossings, the management techniques stressed the importance of education campaigns in warning the public about the dangers of illegal crossings.
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  • 39
    ISSN: 1572-8773
    Keywords: copper ; mercury ; rat ; tooth fillings ; zinc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The aim of this study was to measure the distribution of mercury, in tissues of rats exposed to amalgam over a two months period. Possible interaction of mercury with copper and zinc in organs was also evaluated. Rats were either exposed to mercury from 4 dental amalgams, or fed the diet containing powdered amalgam during two months. Mercury was measured in the kidney, liver and brain, copper in kidney and brain and zinc in kidney. The results showed significantly higher concentrations of mercury in the kidneys and the brains of rats in both exposed groups compared to control. Even after two months of exposure to mercury brain mercury concentration in rats with amalgam fillings was 8 times higher than in the control and 2 times higher than in rats exposed to amalgam supplemented diet. The highest mercury concentration in the latter group was found in the kidneys and it was 5 times higher than in the control group. We found no significant differences between mercury levels in exposed and control rat's liver. Exposure to mercury from dental amalgams did not alter the concentrations of copper and zinc in the tissues. Histopathological analyses of rats tissues did not show any pathological changes. These results support previously proposed nose-brain transport of mercury released from dental amalgam fillings.
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  • 40
    ISSN: 1436-5073
    Keywords: first-order derivative ; Spectrophotometry ; copper ; mercury ; lead ; dithizone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A first-order derivative spectrophotometric method has been developed for the simultaneous determination of copper, mercury and lead at μg/L levels using dithizone as reagent. The procedure involves the simultaneous extraction of these elements by dithizone in chloroform from weakly alkaline solutions. Linear calibration curves were obtained in the ranges 0.5–10 (Cu), 1–10 (Hg) and 1–10 (Pb) μg present in 40 ml of aqueous phase with detection limits of 5 μg/L (Cu) and 20 μg/L (Hg and Pb). The R.S.D.s for 100 μg/L of copper, mercury and lead were 2.5, 2.6 and 3.1% respectively, for 5 determinations. The method is applicable for the determination of copper and lead in marine sediment samples with good precision and accuracy.
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  • 41
    ISSN: 1436-5073
    Keywords: mercury ; soil ; atomic absorption spectrometry ; microwave digestion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Several decomposition procedures and their influence on the determination of mercury by electrothermal (ET) and cold vapour (CV) atomic absorption spectrometry (AAS) have been studied. Soil samples were decomposed by microwave digestion in closed and open vessels as well as by digestion under reflux according to German standard. The use of different acids (HNO3, HCl or aqua regia) was evaluated and compared in respect to their influence on the determination of mercury by ET AAS and CV AAS. The digestion solutions were analyzed by ET AAS with a palladium modifier and by CV AAS using SnCl2 or NaBH4, as reducing agents. The detection limits obtained with different procedures were also evaluated. For the soil containing 6.25 μg/g of Hg the ET AAS measurements were possible. In the case of lower concentration of mercury the CV AAS determination following the microwave digestion procedure with HCl or aqua regia is recommended. The accuracy of the proposed procedure was confirmed by the determination of total mercury in SRM 2711 Montana Soil.
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  • 42
    ISSN: 1436-5073
    Keywords: mercury ; fish ; collaborative study ; atomic absorption spectrometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract One of the major analytical problem in the analysis of fish tissues for total mercury is the dissolution of the sample. This paper compares two different methods of wet digestion (microwave and closed pressurized vessel), followed by FIAAS as final determination and a Zeeman-solid-sample-AAS determination method without previous mineralization. Six fish samples were selected for this study. The top, the central and the bottom portions of the fish were analyzed separately. The mercury contents in the bottom portions determined by Zeeman-solid-sample-AAS were significantly higher than those obtained by the other two systems. A good correlation was observed among the results of the different techniques.
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  • 43
    ISSN: 1436-5073
    Keywords: mercury ; methylmercury ; ethylmercury ; electrochemical probe ; glucose enzyme probe
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Hg(II), methylmercury and ethylmercury have been determined with an electrochemical glucose probe. Mercury and its compounds inhibit the enzyme invertase which, in presence of its substrate, sucrose, produces glucose. When invertase is in presence of mercury its activity decreases; this causes a decrease of glucose production, which is monitored by the glucose sensor and correlated to the concentration of mercury in solution. Parameters such as pH, enzyme concentration, substrate concentration, and reaction and incubation time were optimized. Results showed that mercury, methylmercury and ethylmercury can be detected directly in aqueous solution in the range 2–10 ng/ml.
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  • 44
    ISSN: 1436-5073
    Keywords: electrothermal atomization atomic absorption spectrometry ; mercury ; sea water ; modifiers ; palladium nitrate ; magnesium nitrate ; reduced palladium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A comparative study of different chemical modifiers in graphite furnace atomic absorption spectrometry for the direct determination of mercury in sea water samples, in synthetic sea water sample of high (72.8%) and low 34.2%) salinity and in aqueous solutions, was carried out. The use of reduced palladium produces better results. The mixture of palladium nitrate and ascorbic acid, gives the best limit of detection (1.9 μgl−1). The use of reduced palladium and magnesium nitrate produced excellent recoveries (close to 100%) in the whole salinity range for all mercury concentration tested. The use of palladium nitrate alone or combined with magnesium nitrate gave good recoveries with respect to a real sea water sample for low salinities. The interference from the major components of sea water were completely removed by using reduced palladium and magnesium nitrate modifiers. Thus, a single calibration curve with synthetic sea water may be applied to the analysis of sea water samples of widely differing salinities.
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  • 45
    ISSN: 1436-5073
    Keywords: microwave digestion ; fish ; mercury ; CVAAS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Food samples digestion, in view to quantify total mercury, is the first step to perform before measuring mercury by cold vapour atomic absorption spectrometry (CVAAS). We have compared two microwave digestion systems, one working at atmospheric pressure (open system) and the other one under pressure (closed system). Results obtained for fish muscle samples by the two methods are in good agreement. However, fat is not digested in the open system, whereas in the closed system no more fat remains in the final solution. During the quantification step, applying the CVAAS technique, we have noticed that the choice and the concentration of the reductant solution is very important to obtain good results. Elaborated methods have been validated using certified reference materials.
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  • 46
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    Microchimica acta 127 (1997), S. 225-228 
    ISSN: 1436-5073
    Keywords: mercury ; ET-AAS ; analysis ; matrix reduction
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    Topics: Chemistry and Pharmacology
    Notes: Abstract ET-AAS is investigated for the analysis of high purity mercury. Two possibilities are proposed: ET-AAS determination of trace analytes in the presence of high mercury concentrations or after matrix separation by reduction. The ET-AAS analysis of high-purity mercury under optimal instrumental parameters permits fast and reproducible determination of 0.03 μgg−1 Al, Cd and Mn; 0.05 μgg−1 Cu, Co, Cr, Fe, Ni and Pb and 0.2 μgg−1 V. Preliminary mercury matrix reductive separation with ascorbic acid allows determination of 0.005 μgg−1 Cd, 0.02 μgg−1 Cu, Cr and Mn, 0.03 μg g−1 Co, Ni and Pb, 0.05 μg g−1 Al and Fe and 0.1 μgg−1 V, but the reproducibility is lower. The main advantage of the second procedure is that it avoids laboratory and instrument pollution with toxic mercury.
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  • 47
    ISSN: 1436-5073
    Keywords: mercury ; flotation spectrometry ; paper industry effluents ; orthogonal array design ; brilliant green
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    Topics: Chemistry and Pharmacology
    Notes: Abstract This paper describes a sensitive spectrophotometric method for the determination of mercury, based on the flotation of a mercury iodide-brilliant green complex with cyclohexane at pH 5 and dissolution of the complex in acetone. The absorbance of the complex is measured at 625 nm. Beer's law is obeyed from 4–500 μg/l of mercury. The method is highly sensitive (ɛ = 5.96 × 105 1 mol−1 cm−1) and selective, as it is free from interferences by almost all cations and anions in the presence of EDTA. Furthermore, a two-level orthogonal array design as a chemometric method has been used for optimization of the various parameters involved. The method has been successfully applied to paper industry effluents.
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    Microchimica acta 130 (1999), S. 209-214 
    ISSN: 1436-5073
    Keywords: mercury ; copper ; acid urease ; ammonium optode
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    Topics: Chemistry and Pharmacology
    Notes: Abstract We report on a quick and simple test based on enzyme inhibition for the detection of mercury and copper using free acid urease coupled to an optical sensor system. Lipophilized Nile Blue was incorporated in plasticized poly(vinyl chloride) (PVC) to produce an ammonium-sensitive layer with a thickness of around 4 μm. The layer was fixed on one side of a disposable cuvette. A solution of buffer, enzyme and heavy metals was placed into the thermostated cell. Enzymatic hydrolysis was started upon addition of urea and the formation of ammonium was monitored. Mercury and copper were the strongest inhibitors; for this reason the inhibitory efficiency of these metals was examined in citrate, acetate and trismaleate buffers. The cuvette test was most sensitive and selective for mercury in a citrate buffer. The limit of detection for mercury(II) ions was as low as 1 μg/L. Copper ions do not interfere because of complexation by citrate. The inhibitory effects of metal combinations on the activity of acid urease and the effects of optimum pH of the enzyme and the transducer on the dynamic range of the cuvette test are presented.
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  • 49
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    Journal of risk and uncertainty 15 (1997), S. 241-257 
    ISSN: 1573-0476
    Keywords: Contingent valuation ; risk assessment ; social distrust
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    Topics: Economics
    Notes: Abstract Distrust of social institutions is becoming an important component of risk communication and policy analysis. To assess the impact of social distrust on decision making, we examine the role of distrust of information sources on the willingness to accept a hazardous waste disposal facility in one's neighborhood. Using a prospective-reference utility model, distrust of information sources is analyzed a possible influence on individual choice in a risk-benefit tradeoff. Using contingent valuation survey data on the siting of a hazardous waste disposal facility, we find that respondents are particularly distrustful of both governmental officials and waste disposal businesses. We find that social distrust increases the perceived risk of a facility and influences the likelihood of accepting a referendum to site a hazardous waste disposal facility. The level of compensation offered in the contingent valuation scenario also is found to influence a respondent's risk perception.
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  • 50
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    Nutrient cycling in agroecosystems 50 (1998), S. 271-276 
    ISSN: 1573-0867
    Keywords: nitrogen ; monitoring ; dairy farming ; simulation models ; risk assessment ; soil variability
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    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract At the ‘De Marke’ experimental farm a dairy farm was set up with the aim of meeting environmental and economic goals. The farm management with respect to nitrogen emphasized reduction of fertilization and a cattle grazing system that should result in nitrate concentrations in the groundwater below the EC-directive level of 11.3 mg l-1 nitrate-N. At six sites in six different fields of ‘De Marke’, these concentrations were monitored for 4 years. A direct comparison with the chosen limit was possible for these sites, but an evaluation of the environmental achievements of the farming system at farm level was also required. This was achieved by using simulation models and additional information about soils and field management. Based on multiple soil profile descriptions, frequency distributions of model output were generated, allowing a risk assessment for the total farm. The probability of exceeding the chosen threshold value of 11.3 mg l-1 nitrate-N during the period of summer 1991- spring 1995 was 63% for the whole farm, with marked differences between years, crops and hydrological conditions.
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  • 51
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    Natural hazards 20 (1999), S. 279-294 
    ISSN: 1573-0840
    Keywords: risk assessment ; groundwater contamination ; vulnerability ; GIS ; hazard ; economic ; value
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract The groundwater contamination risk map of a samplealluvial area was produced by using the IlwisGeographical Information System (GIS) to construct andto overlay thematic maps. The risk map has beenderived from the vulnerability map, the hazard map,where the potential contaminating sources wereidentified, and the socio-economic value of thegroundwater resource, represented by the wells. Thegroundwater quality map allowed thereliability of hazard and risk maps to be tested. The final map shows interesting results and stressesthe need for the GIS to test and improve on thegroundwater contamination risk assessment methods.
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  • 52
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    Journal of thermal analysis and calorimetry 56 (1999), S. 1219-1232 
    ISSN: 1572-8943
    Keywords: environmental monitoring ; indoor environments ; museums and galleries ; risk assessment ; tempera paint dosimeters
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    Topics: Chemistry and Pharmacology
    Notes: Abstract This paper describes the results and conclusions of research directed towards the development and evaluation of a chemical sensor which would provide information on the quality of indoor environments surrounding cultural objects. In our case these objects were paintings housed in major European galleries and the main objective is their preservation through an improved understanding of their microenvironment. The concept was to prepare and expose test tempera paintings which would behave as dosimeters and integrate the environmental response at these locations. Artificial ageing of similar samples was performed to provide a means of calibrating the test paintings. Samples from the test paintings were compared with artificially aged samples and this enabled the sites to be ranked in terms of their suitability for exposure of cultural objects. Additionally, novel methodology involving piezoelectric sensors was designed for monitoring the relative humidity and temperature of the microenvironment of paintings. Dielectric techniques were also used for measuring the effect of relative humidity fluctuations on artists' materials and novel non-invasive dielectric techniques in the microwave region were used for the determination of their moisture content.
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  • 53
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    Environmental and resource economics 11 (1998), S. 489-501 
    ISSN: 1573-1502
    Keywords: cost-benefit analysis ; environmental policy ; precautionary principle ; risk assessment ; sustainable development
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    Topics: Energy, Environment Protection, Nuclear Power Engineering , Economics
    Notes: Abstract Revisions to the European Treaty of Union require some form of environmental appraisal – primarily risk assessment and cost-benefit analysis – of regulatory initiatives by the European Commission. A retrospective look at the emergence of environmental appraisal also shows that, while the Commission has made great advances in introducing cost-benefit or cost-effectiveness appraisals in recent years, past environmental decisions and overall environmental policy have not been informed by systematic appraisal techniques. Nor is it clear what role is now being played by risk assessments. While it is impossible to gauge the extent to which systematic appraisal procedures will save on regulatory and compliance expenditures, some indications are provided of the costs of past neglect of these procedures.
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  • 54
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    Water, air & soil pollution 85 (1995), S. 823-828 
    ISSN: 1573-2932
    Keywords: fish ; mercury ; lake chemistry ; biomagnification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract We determined mercury in fish (perch Perca fluviatilis) from 26 Russian lakes in three regions over four years. The lakes ranged in size from 2 to 395,000 ha, in pH from 4.5 to 10.0, and in color from 3 to 190 hazen. Sixteen lakes were drainage lakes, with permanent outlets, and 10 were seepage lakes, with no permanent inlets or outlets. The lakes were generally located in forested regions with little or no human habitation in the watershed. The three regions were geologically distinct: Precambrian Shield granitic bedrock covered with thin soil; Triassic bedrock covered with thick glacial tills; and Triassic bedrock covered with thin sediments. At each lake water samples were collected and analyzed for pH, add neutralizing capacity (ANC), major cations, and anions. Dissolved mercury species were estimated with a thermodynamic equilibrium model (MINTEQA2). Mercury content of dorsal muscle varied from 0.04 to 1.0 μg/g wet weight, and was linearly related to calculated HgCH3Cl (r20.68, p〈0.001). Lake HgCH3Cl, in turn, was related to lake pH (r2=0.86, p〈0.001). Stepwise multiple regression selected lake HgCH3Cl and color as the factors most highly related to fish mercury content, with the model accounting for 75% of the variation.
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    Water, air & soil pollution 80 (1995), S. 325-335 
    ISSN: 1573-2932
    Keywords: Atmospheric chemistry ; mercury ; plume model
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    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A reactive plume model that includes atmospheric chemical reactions of mercury was developed. The model simulates advective transport with the mean wind flow; horizontal and vertical turbulent diffusion; gas phase; aqueous-phase and particulate chemistry; cloud microphysics; wet deposition and dry deposition. The model was applied to the simulation of clear sky, non-precipitating cloud and precipitating cloud scenarios. No significant mercury chemistry occurs in the absence of droplets. In clouds, Hg(II) is reduced to Hg(0) with more reduction taking place in precipitating clouds than in non-precipitating clouds.
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    Water, air & soil pollution 80 (1995), S. 1209-1216 
    ISSN: 1573-2932
    Keywords: gaseous ; particulate ; mercury ; sampling ; silver ; gold ; denuder
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    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A denuder-based method for sampling and separating gaseous and participate mercury in the air is described. Two different denuder configurations developed in Vilnius, Lithuania (silver) and in Gothenburg, Sweden (gold) are compared. Data were acquired at different sampling locations around the cities of Vilnius and Gothenburg. The concentration of particulate Hg was found to be 0.04 to 0.40 ng m−3 in the Vilnius region, and 0.11 to 0.57 ng m−3 in the Gothenburg region. Intel-calibration results for the silver and gold denuders are presented. The results obtained by the two different denuder configurations and sampling set-ups display satisfactory agreement.
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  • 57
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    Water, air & soil pollution 85 (1995), S. 167-176 
    ISSN: 1573-2932
    Keywords: air pollution ; health effects ; risk assessment
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    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Based on combined information available from air quality monitoring data and long-range transport models, European population exposure to SO2, NO2 and O3 has been estimated. This information has been combined with the results of epidemiological studies assessing strength of association between the exposure and health effects to estimate an impact of the pollution on health in Europe. The analysis indicates that a considerable number of health problems, ranging from mild irritation of the respiratory system to increased mortality, can be attributed to short-term peaks of pollution observed in Europe. Chronic impacts of prolonged elevated SO2 levels on lung function are estimated to occur in close to10 million people in Europe.
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    Water, air & soil pollution 89 (1996), S. 267-275 
    ISSN: 1573-2932
    Keywords: mercury ; forest trees ; biomonitors ; contaminants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The concentration of mercury has been determined in assimilation organs of forest trees from 10 main industrial regions of Slovakia, four mountain forests and one military area and compared with concentration of mercury from 1356 permanent monitoring plots of Slovakia. The mercury concentration ranges for 2 yr old needles of Picea abies Karst. were (in mg kg−1): 1.249–4.402 (Rudnany iron ore mines), 0.013–0.749 (nine other industrial regions), 0.021–0.737 (four mountain forests) and 0.053–0.538 (military area). The mercury content in the soil (0–5 cm) from a mercury smelting plant ranged from 9.9 to 130 mg kg−1, and the moss Pleurozium schreberi contained 3.8–9.1 mg kg−1. The values obtained were compared with the available literature data.
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  • 59
    ISSN: 1573-2932
    Keywords: acid rain ; batch experiment ; Freundlich isotherm ; lysimeter experiment ; mercury ; simulation model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Increasing mercury contents are reported from freshwater systems and fish in northern Europe and North America. Mercury input from soils is a major source with the leaching being affected by increased atmospheric mercury deposition compared to pre-industrial times and by other environmental conditions such as acid rain. The results of a mathematical model-calculation of vertical inorganic Hg(II) leaching in a Scandinavian iron-humus podzol under different atmospheric input rates of mercury are presented. Leaching under background rain conditions was calculated to be considerably stronger than under acid rain conditions. Increasing fractions of deposited soluble or solute atmospheric mercury were leached from the O f(h)-horizon with decreasing soil content of soluble mercury under acid rain conditions; this effect was less pronounced under background rain conditions. The steady state concentrations of soluble mercury of the upper soil horizons were calculated and compared with the actual concentrations of total (= soluble + insoluble mercury) and extractable (= estimate of soluble) mercury measured in these horizons. The results indicate that even if the deposition of airborne mercury to soil is strongly reduced, the total mercury content of the soil decreases only slowly. It may take decades or even centuries before a new steady state concentration of total mercury is established in the soil. The decrease of the mercury concentration in the O f(h)-horizon is probably largely dependent on the turnover of organic matter, binding most of the deposited airborne mercury in an insoluble form. Hence, present day mercury leaching is likely to be dominated by mercury deposited during former times and temporarily retained in an insoluble form in the organic matter.
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  • 60
    ISSN: 1573-2932
    Keywords: mercury ; foodplains ; humic substances ; complexation ; speciation ; mobilization ; risk assessment ; water solubility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The water-mobilizability of mercury from contaminated floodplain soils of the river Elbe in Northern Germany was evaluated by batch extraction experiments. It was shown that only a small amount of the total mercury present (about 1% per extraction) can be mobilized by water. This mercury is transported entirely in the form of a complex bound to humic acids (HA); particulates and fulvic acids (FA) did not seem to contribute to the process. It could not be removed from the HA even at pH 1, indicating an extremely strong complexation e.g. by sulfur-containing ligands. Furthermore, the influence of pH on the mobilization was investigated. It was found that in the range of natural pH-values, there was no observable effect of pH on the mobilization of either mercury or dissolved organic carbon (DOC). This surprising finding is explained by an unexpectedly high buffering capacity of the humics, both in the acidic and in the alkaline region. Only at extreme pH-values there was deviation from this behaviour. In contrast to other heavy metals, the amount of mobilized mercury decreases at pH 〈 3; and at pH 〉 12, an increased mobilization of mercury was observed because the humics are mobilized completely, accompanied by the total amount of mercury bound to them.
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  • 61
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    Water, air & soil pollution 97 (1997), S. 205-207 
    ISSN: 1573-2932
    Keywords: mercury ; gold mining ; ecosystems ; methyl-Hg ; cycling ; global sources
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract As described by Jemelov and Ramel (1995), the Scientific Committee on Problems of the Environment (SCOPE) sponsored an investigation of Hg in ecosystems with special emphasis on tropical regions. In these regions small-scale gold mining activities have occupied about 10 million people worldwide who use Hg for extracting gold.
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  • 62
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    Water, air & soil pollution 97 (1997), S. 257-263 
    ISSN: 1573-2932
    Keywords: mercury ; atmosphere ; rainwater ; marine
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    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Total gaseous mercury (TGM) and rainwater were collected on board of two research vessels (F. S. ALKOR and R.V. BELGICA) positioned 200 km apart in the center of the North Sea during the North Sea Experiment, September 1991. On the F. S. ALKOR (up-wind ship) TGM concentrations ranged from 0.7 to 2.6 ng·m−3 with an average of 1.5 ng m−3 and on the R. V. BELGICA (down-wind ship) TGM ranged from 0.7 to 1.9 ng·m−3 with an average of 1.2 ng·m−3. An average 20% decrease is observed from the up-wind to the down wind ship. which may largely be affected by entrainment into the free troposphere. An overall removal (entrainment) velocity of 0.95 cm·s−1 was calculated for the whole experiment. The average removal velocity was 0.5 cm·s−1 for dry periods and varied between 1 to 5 cm·s−1 during rain events. Rainwater concentrations varied between 5 and 25 ng·1−1. Based on these data an annual wet deposition flux of 1.08 ng Hg cm−2 yr1− was estimated for the North Sea.
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  • 63
    ISSN: 1573-2932
    Keywords: mercury ; methylmercury ; sediment ; polychaete ; Nereis diversicolor ; methylation ; bioaccumulation ; Scheldt estuary
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Total mercury (Hg) and methylmercury (MeHg) concentrations were determined in sediments and in the polychaete worm Nereis diversicolor at 13 stations of a brackish water intertidal mudflat of the Scheldt estuary. Hg and MeHg concentrations in sediments ranged from 144 to 1192 ng g−1 dw and from 0.8 to 6 ng g−1 dw, respectively. Both Hg and MeHg concentrations increased with an increase of organic matter (OM) content and fine grain fraction. In contrast, Hg accumulation by N. diversicolor was significantly (p 〈 0.05) higher at stations with sandy sediments (mean value: 125 ng g−1 dw) than at stations with muddy sediments (mean value, 80 ng g−1), probably because Hg availability for bioaccumulation at muddy stations was reduced by high OM content of the muddy sediments. MeHg accounted for an average of 0.7% of the total Hg in sediments and 18% of the total Hg in N. diversicolor. Seasonal variations significantly affected Hg concentrations in sediments and MeHg in N. diversicolor. Total Hg concentrations in sediments were significantly (p 〈 0.05) higher in autumn and winter than in spring and summer whereas MeHg concentrations were lowest in winter compared to the other seasons. On the other hand, total Hg concentrations in the worms were lowest in spring whereas MeHg concentrations were significantly (p 〈 0.01) higher in spring and summer than in autumn and winter.
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  • 64
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    Water, air & soil pollution 99 (1997), S. 217-223 
    ISSN: 1573-2932
    Keywords: selective leach ; organic ; humic ; fulvic ; analysis ; mercury ; zinc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The international reference lake sediment, LKSD-4, was used to compare Hg, organic C and Zn extracted from its ‘soluble organic’ phase by two commonly used reagents: 0.1 M Na4P2O7 solution at pH 10 and 0.5 M NaOH solution at pH 12. While recoveries of Hg and Zn by 0.1 M Na4P2O7 are not affected by changes in sample weight to reagent volume ratio (W/V) or contact time, those by NaOH show a marked dependency. In general, the NaOH leach extracts more organic C and Hg from LKSD-4 but less Zn. Over the range of conditions studied, the NaOH-based method extracted 4.7–9.8% C, 27–103 ng g−1 Hg and 19–69 μg g−1 Zn from LKSD-4, compared to 2.3–2.8% C, 17–24 ng g−1 Hg and 64–72 μg g−1 Zn by the Na4P2O7 leach. Clearly, different groups of organic substances are being dissolved by these two reagents and therefore a comparison of data from different laboratories becomes meaningless. This paper suggests that more research is needed into the exactNature of metal-organic associations extracted by selective leaches and into associated artifacts of extraction such as readsorption phenomena.
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  • 65
    ISSN: 1573-2959
    Keywords: risk assessment ; chlorinated compound ; environmental ; marine ; exposure ; aquatic toxicity ; monitoring ; trichloroethylene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract This risk assessment on trichloroethylene (TRI) was carried out specifically for the marine environment, according to the methodology laid down in the EU risk assessment Regulation (1488/94) and the Guidance Document of the EU New and Existing Substances Regulation (TGD, 1997). The study consists of the collection and evaluation of data on effects and environmental concentrations from analytical monitoring programs in large rivers and estuaries in the North Sea area. The risk is indicated by the ratio of the "predicted environmental concentrations" (PEC) and the "predicted no effect concentrations" (PNEC) for the marine aquatic environment. In total, 19 studies for fish, 30 studies for invertebrates and 14 studies for algae have been evaluated. Both acute and chronic toxicity studies have been taken into account and the appropriate assessment factors have been used to define a PNEC value of 150 µg/l. Most of the available monitoring data apply to rivers and estuaries and were used to calculate PECs. The most recent data (1991-1995) support a typical PEC of 0.1 µg TRI/l water and a worst case PEC of 3.5 µg TRI/l water. The calculated PEC/PNEC ratios give a safety margin of 40 to 1,500 between the predicted no effect concentration and the exposure concentration. Additional evaluation of environmental fate and bioaccumulation characteristics showed that no concern for food chain accumulation is expected.
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    Environmental monitoring and assessment 59 (1999), S. 225-247 
    ISSN: 1573-2959
    Keywords: cross-cultural ; perceived risk ; risk ; risk analysis ; risk assessment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract This study examines perceived risk data from the U.S., China, Japan, and South Korea. These data are then compared with similar results collected from previous studies. Psychometric scaling scores from Burkino Faso (a West African Country), France, Norway, and Hungary have been analyzed and compared with results from our study. The data reveal certain risk events like nuclear weapons, war, and AIDS to have high perceived risks in all countries. These data also show that many of the events have dissimilar perceived risks in different countries. The conclusions also show some countries have higher over all levels of perceive risk (South Korea) while others like the United States display generally lower values.
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    Environmental geochemistry and health 19 (1997), S. 101-112 
    ISSN: 1573-2983
    Keywords: Air pollution ; mercury ; Idrija mine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Medicine
    Notes: Abstract Idrija mine, the second largest mercury mine in the world, was in use since 1490. More than 107 000 tons of Hg were produced in its five centuries of history until 1990 when production was reduced to a few hundred kilos per year. The average recovery rate of mercury has been estimated to 73%; much of the remaining 27% was dissipated into the environment. In spite of present minimal levels of production, and only a few days of smelter operation per year, a real time survey with a mercury Zeeman analyser in a car showed relatively high mercury concentrations in the air. Amounts of 300--4000 ng Hg m-3 have been found around both the major sources of mercury vapour, the smelter and mine ventilation shaft -- while the amounts at the Old Place, at the City Museum, and near the Nikova-Idrijca confluence are of the order of 50 ng m-3. Polluted air will be transported from those sources to a degree which depends on the weather conditions, mainly the direction and intensity of the wind. The high mercury contents in the air are not only due to anthropogenic sources (smelter and the ventilation shaft, dumps and smelter slag used in construction), but may also partly be natural as in the Pront area, where the outcropping bedrock contains native mercury.
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    Environmental modeling and assessment 4 (1999), S. 165-178 
    ISSN: 1573-2967
    Keywords: exposure assessment ; ground water contamination ; risk assessment ; spatial variability ; geostatistical analysis ; deterministic modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract This paper describes a new methodology for modeling contaminant transport in ground water for (1) better quantifying the magnitude of exposure in a contaminated aquifer, (2) characterizing the spatial and temporal variation of exposure in a heterogeneous aquifer, and (3) providing more tools for characterizing population exposure. This methodology is also applied to a semi-hypothetical case study.
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    Environmental and ecological statistics 3 (1996), S. 81-97 
    ISSN: 1573-3009
    Keywords: gamma distribution ; left censoring ; product limit estimate ; risk assessment ; truncated normal distribution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A frequent assumption in environmental risk assessment is that the underlying distribution of an analyte concentration is lognormal. However, the distribution of a random variable whose log has a t-distribution has infinite mean. Because of the proximity of the standard normal and t-distribution, this suggests that a distribution such as the gamma or truncated normal, with smaller right tail probabilities, might make a better statistical model for mean estimation than the lognormal. In order to assess the effect of departures from lognormality on lognormal-based statistics, we simulated complete lognormal, truncated normal, and gamma data for various sample sizes and coefficients of variation. In these cases, departures from lognormality were not easily detected with the Shapiro-Wilk test. Various lognormal-based estimates and tests were compared with alternate methods based on the ordinary sample mean and standard error. The examples were also considered in the presence of random left censoring with the mean and standard error of the product limit estimate replacing the ordinary sample mean and standard error. The results suggest that in the estimation of or tests about a mean, if the assumption of lognormality is at all suspect, then lognormal-based approaches may not be as good as the alternative methods.
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    Ecotoxicology 5 (1996), S. 59-81 
    ISSN: 1573-3017
    Keywords: pesticides ; synergism ; risk assessment ; wildlife
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Reviews of pesticide usage survey data and vertebrate wildlife and honeybee poisoning incident schemes in the UK show that there is considerable potential for wildlife to be exposed to combinations of agricultural pesticides. According to the published literature the toxicity of many pesticide combinations is at least additive. In some cases pesticide mixtures, particularly those involving insecticides, have been shown to be synergistic, with reported increases in toxicity of up to 100-fold. However, these effects are species, time and dose dependent and are therefore difficult to predict routinely. It is suggested that risk assessments should routinely take additive toxicity into account and those based on synergism should be targeted at those mixtures for which a further defined increase in toxicity would result in a high-risk classification. In order to support this risk assessment approach there is a need to develop and validate a standard in vivo test in order to confirm the interaction in those cases where additive or synergistic toxicity results in a high-risk classification.
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    Ecotoxicology 5 (1996), S. 139-144 
    ISSN: 1573-3017
    Keywords: ED point ; NOEL ; risk assessment ; pesticides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: The availability and use of ED point and NOEL values in ecotoxicological data submitted to the UK Pesticides Safety Directorate is explored. In first tier data normally submitted for pesticide registration, ED points such as EC/LC/LD50s are commonly available from acute laboratory toxicity studies conducted using birds, small mammals, fish, aquatic invertebrates, plants, honeybees and earthworms. These ED points are subsequently used for hazard classification of the pesticide and in toxicity: exposure ratio (TER) calculations required during the acute risk assessment. Although NOELs can often be available from the same first tier data, they are generally not used. However, NOELs commonly available from higher tier chronic toxicity studies such as chronic fish, Daphnia reproduction and avian reproduction studies, are used in TER calculations to assess chronic risk. The statistical limitations of the NOEL are recognized and the regulatory implications of replacing the NOEL with an alternative ED point are discussed.
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  • 72
    ISSN: 1573-3017
    Keywords: fish ; mercury ; natural selection ; allozyme ; population
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Measurements of the differential tolerance between enzyme genotypes and shifts in allozyme frequencies in populations from contaminated habitats have prompted the use of allozymes as markers of population-level toxicant effects. However, such studies often do not consider other factors that influence allele frequencies, including natural clines, migration, the intensity and specificity of selection and toxicant-induced genetic bottlenecks. In addition, selection components other than survival are not included. Consequently, the associated conclusions remain speculative. To assess this approach rigorously, a simulation study was conducted with the mosquitofish (Gambusia holbrooki) GPI-2 locus. Laboratory studies have shown the GPI-238/38 homozygote at this locus to be less tolerant than other genotypes during acute exposure to mercury. The GPI-2100/100 genotype has also been shown to have a reproductive disadvantage at lower mercury concentrations. Simple and then more complex models were used to quantify the relative effects of viability selection, random genetic drift and migration on the GPI-238 allele frequency. Simulations were also performed to assess the contribution of sexual and fecundity selection. A simple population model suggested that viability selection plays a greater role than does mortality-driven, genetic drift in the decrease of the sensitive allele under the conditions of this study. A more complex, stochastic model indicated that no significant mortality-driven drift was taking place in this system. In both models, migration mitigated the effect of selection. Sexual and fecundity selection had little effect on the allele frequencies in these simulations. We conclude that, provided the system under study is clearly understood, shifts in allele frequency can indicate the population-level effects of pollutants.
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  • 73
    ISSN: 1573-4919
    Keywords: mercury ; rat kidney ; mitochondria ; oxidative phosphorylation ; FoF1-ATPase ; ATP synthesis ; ATP hydrolysis ; oxidative stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The effects of Hg(II) on bioenergetic and oxidative status of rat renal cortex mitochondria were evaluated both in vitro, and in vivo 1 and 24 h after treatment of animals with 5 mg HgCl2/kg ip. The parameters assessed were mitochondrial respiration, ATP synthesis and hydrolysis, glutathione content, lipid peroxidation, protein oxidation, and activity of antioxidant enzymes. At low concentration (5 µM) and during a short incubation time, Hg(II) uncoupled oxidative phosphorylation while at slightly higher concentration or longer incubation time the ion impaired the respiratory chain. The rate of ATP synthesis and the phosphorylation potential of mitochondria were depressed, although inhibition of ATP synthesis did not exceed 50%. In vivo, respiration and ATP synthesis were not affected 1 h post-treatment, but were markedly depressed 24 h later. ATP hydrolysis by submitochondrial particle FoF1-ATPase was inhibited (also by no more than 50%) both in vitro, and in vivo 1 and 24 h post-treatment. Hg(II) induced maximum ATPase inhibition at about 1 uM concentration but did not have a strong inhibitory effect in the presence of Triton X-100. Oxidative stress was not observed in mitochondria 1 h post-treatment. However, 24 h later Hg(II) reduced the GSH/GSSG ratio and increased mitochondrial lipid peroxidation and protein oxidation, as well as inhibited GSH-peroxidase and GSSG-reductase activities. These results suggest that the following sequence of events may be involved in Hg(II) toxicity in the kidney: (1) inhibition of FoFl-ATPase, (2) uncoupling of oxidative phosphorylation, (3) oxidative stress-associated impairment of the respiratory chain, and (4) inhibition of ATP synthesis.
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  • 74
    ISSN: 1573-9368
    Keywords: transgenic oilseed rape (Brassica napus) ; risk assessment ; honey bee (Apis mellifera) ; foraging behaviour ; nectar secretion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The impact of genetically modified oilseed rape (Brassica napus L.) on the foraging behaviour of honey bees (Apis mellifera L.) was evaluated on two different lines transformed to express constitutively heterologous chitinase in somatic tissue for enhanced disease resistance. Experiments were conducted in confinement in an indoor flight room with controlled conditions and in an outdoor flight cage with conditions more representative of the open environment. Foraging behaviour was analysed by observations of general bee behaviour (total number of visits) and of individual bee behaviour (using a video camera coupled with a special software program to process the data). The plants were analysed in terms of nectar quantity and quality (nectar volume and sugar content). The results showed no effects on bee foraging behaviour due to the modification of the genome of these plants by the introduction of a chitinase gene even though some differences between lines were found in the nectar. The methods applied in this original approach for the evaluation of the impact of genetically modified oilseed rape were shown to be sufficiently sensitive to detect changes in bee behaviour resulting from differences between plants.
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  • 75
    ISSN: 1573-9368
    Keywords: Pathogen-derived resistance ; cucumber mosaic virus ; environmental safety issues ; virus-vector specificity ; heterologous encapsidation ; recombination ; aphid- mediated virus spread ; field experiments ; risk assessment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Transgenic melon and squash containing the coat protein (CP) gene of the aphid transmissible strain WL of cucumber mosaic cucumovirus (CMV) were grown under field conditions to determine if they would assist the spread of the aphid non-transmissible strain C of CMV, possibly through heterologous encapsidation and recombination. Transgenic melon were susceptible to CMV strain C whereas transgenic squash were resistant although the latter occasionally developed chlorotic blotches on lower leaves. Transgenic squash line ZW-20, one of the parents of commercialized cultivar Freedom II, which expresses the CP genes of the aphid transmissible strains FL of zucchini yellow mosaic (ZYMV) and watermelon mosaic virus 2 (WMV 2) potyviruses was also tested. Line ZW-20 is resistant to ZYMV and WMV 2 but is susceptible to CMV. Field experiments conducted over two consecutive years showed that aphid-vectored spread of CMV strain C did not occur from any of the CMV strain C-challenge inoculated transgenic plants to any of the uninoculated CMV-susceptible non- transgenic plants. Although CMV was detected in 3% (22/764) of the uninoculated plants, several assays including ELISA, RT- PCR-RFLP, identification of CP amino acid at position 168, and aphid transmission tests demonstrated that these CMV isolates were distinct from strain C. Instead, they were non-targeted CMV isolates that came from outside the field plots. This is the first report on field experiments designed to determine the potential of transgenic plants expressing CP genes for triggering changes in virus-vector specificity. Our results indicate that transgenic plants expressing CP genes of aphid transmissible strains of CMV, ZYMV, and WMV 2 are unlikely to mediate the spread of aphid non-transmissible strains of CMV. This finding is of practical relevance because transgenic crops expressing the three CP genes are targeted for commercial release, and because CMV is economically important, has a wide host range, and is widespread worldwide.
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  • 76
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    Russian chemical bulletin 44 (1995), S. 724-729 
    ISSN: 1573-9171
    Keywords: carboranes ; mercury ; mercuration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The mercuration of substituted R2C2B10H9X-9 type carboranes (where R=m-H, X= Cl, Br, I, Me; R=o-H, X=Me) was studied. It was found that mercury atoms add to the boron atoms in position 10 ofmeta-carboranes and in position 12 ofortho-carboranes,i.e., to the boron atoms adjacent to the boron atom bonded to the X substituent. Symmetrical (R2C2B10H8X)2Hg type derivatives were obtained. It was shown that they can be used as starting materials in transmetallation reactions.
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  • 77
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    Russian chemical bulletin 45 (1996), S. 1194-1199 
    ISSN: 1573-9171
    Keywords: hardness ; chemical hardness ; mercury ; gold ; exchange equilibria ; 19F NMR spectra
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract 19F NMR spectroscopy was used to study the exchange reactions involving 4-fluorothiophenoxides, 4-nitrophenoxides, chlorides, and acetates of arylmercury and triphenylphosphinegold. The analysis of the data on equilibrium constants allows one to obtain information on the comparative chemical hardness of ArHg+ and Ph3PAu+ cations. The increase in the electron-donating ability of aryl ligands enhances the chemical hardness of ArHg+ cations, their influence being best described by σ0 constants of substituted phenyl groups.
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  • 78
    ISSN: 1573-9368
    Keywords: plant microbiology ; genetically engineered plants ; risk assessment ; Bacillus thuringiensis toxin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The environmental release of genetically engineered (transgenic) plants may be accompanied by ecological effects including changes in the plant-associated microflora. A field release of transgnic potato plants that produce the insecticidal endotoxin ofBacillus thuringiensis var.tenebrionis (Btt) was monitored for changes in total bacterial and fungal populations, fungal species diversity and abundance, and plant pathogen levels. The microflora on three phenological stages of leaves (green, yellow and brown) were compared over the growing season (sample days 0, 21, 42, 63 and 98) for transgenic potato plants, commercial Russet Burbank potato plants treated with systemic insecticide (Di-Syston) and commercial Russet Burbank potato plants treated with microbialBtt (M-Trak). In addition, plant and soil assays were performed to assess disease incidence ofFusarium spp.,Pythium spp.,Verticillium dahliae, potato leaf roll virus (PLRV) and potato virus Y (PVY). Few significant differences in phylloplane microflora among the plant types were observed and none of the differences were persisent. Total bacterial populations on brown leaves on sample day 21 and on green leaves on sample day 42 were significantly higher on the transgenic potato plants. Total fungal populations on gree leaves on sample day 63 were significantly different among the three plant types; lowest levels were on the commerical potato plants treated with systemic insecticide and highest levels were on the commercial potato plants treated with microbialBtt. Differences in fungal species assemblages and diversity were correlated with sampling dates, but relatively consistent among treatments.Alternaria alternata, a common saprophyte on leaves and in soil and leaf litter, was the most commonly isolated fungus species for all the plant treatments. Rhizosphere populations of the soilborne pathogensPythium spp.,Fusarium spp. andV. dahliae did not differ between the transgenic potato plants and the commercial potato plants treated with systemic insecticide. The incidence of tuber infection at the end of the growing season by the plant pathogenV. dahliae was highest for the transgenic potato plants but this difference was related to longer viability of the transgenic potato plants. This difference in longevity between the transgenic potato plants and the commercial + systemic insecticide potato plants also made comparison of the incidence of PVY and PLRV problematic. Our results indicate that under field conditions the microflora of transgenicBtt-producing potato plants differed minimally from that of chemically and microbially treated commerical potato plants.
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  • 79
    ISSN: 1573-5125
    Keywords: phytoplankton ; specific growth rate ; XAD-4 ; XAD-8 ; risk assessment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Laboratory incubation experiments were used to study the effect of reduced concentrations of organic micropollutants in water from the rivers Rhine and Meuse on the specific growth rate of the river phytoplankton community. Before incubation, part of the water sampled was treated with XAD-4 and XAD-8 resins to absorb dissolved organic compounds. Four dilutions were made by mixing untreated water with XAD-treated water in the ratios 100:0 (control), 70:30, 40:60 and 0:100. The phytoplankton specific growth rate increased significantly with the increased fraction treated with XAD in all but one incubation experiment. In these experiments, the specific growth rate was on average 9% higher in the fraction in which 100% was treated with XAD than in the controls. In the Rhine and Meuse river water, phytoplankton growth seemed to be inhibited by organic compounds. This inhibition was ascribed to the presence of dissolved organic micropollutants. Removing organic micropollutants using XAD resins to study the toxic effects of these compounds on field phytoplankton communities can be concluded to be a promising tool for risk assessment of micropollutants but needs to be supported by additional methodological research.
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  • 80
    ISSN: 1573-5125
    Keywords: growth ; Azolla ; eutrophication ; mercury ; India
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The growth ofAzolla was stimulated in different water bodies in Burdwan. It depended on the PO4−P contents of the media. Biomass, chlorophyll and tissue phosphorus content ofAzolla were positively correlated with PO4−P of the different water bodies while chlorophyll content of the fern was positively correlated with conductivity. We concluded that the water bodies of Burdwan can be utilised as sites for large scale multiplication ofAzolla for fertilization purposes in rice cultivation, despite the presence of mercury.
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  • 81
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    Aquatic ecology 29 (1995), S. 291-296 
    ISSN: 1573-5125
    Keywords: mercury ; seasonal inputs ; sediments ; Ria de Aveiro
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Water, suspended particulate matter (SPM) and sediments were collected from the Esteiro de Estarreja (Ria de Aveiro, Portugal), which receives considerable quantities of waste mercury from a chlor-alkali plant. Dissolved and particulate Hg concentrations in the effluent ranged between 4 –167 μg I−1 and 141–3144 μg g−1, respectively, at pH values of 〉10. The effluent plume undergoes significant chemical changes during advection downestuary. The evidence suggested that adsorption of dissolved Hg onto organic-rich SPM was an important process. A maximum sediment Hg concentration of 500 μg g−1 was found about 1.5 km from the discharge, as a result of the settling of Hg-rich SPM. Downestuary Hg concentrations in sediments decline to about 100 μg g−1 at the mouth of the Esteiro. The particle-water interactions are discussed in terms of the transport of dissolved and particulate Hg into the Ria de Aveiro.
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  • 82
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    Biological invasions 1 (1999), S. 89-96 
    ISSN: 1573-1464
    Keywords: base-rate effect ; decision theory ; exotic organisms ; GMO ; loss structure ; quarantine ; risk assessment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Organisms generally become pests at a low rate. As a consequence of this low ‘base-rate probability’, the large majority of organisms rejected in any random sample of potential introductions would probably be harmless, despite the fairly high accuracy of some recently proposed risk assessment systems for exotic introductions. Here we distinguish between a system's accuracy (the proportion of a group of known pest species that would be correctly identified as pests) and reliability (the rate of false positives and false negatives produced once the base-rate is taken into account). We next adapt a decision theory analysis of earthquake prediction to explore when we would be best advised to ignore the recommendations of a screening system for exotic introductions. In one scenario, we show that a pest risk assessment system with an accuracy of 85% would be better ignored, unless the damage caused by introducing a pest is eight times or more that caused by not introducing a harmless organism that is potentially useful. Furthermore, because of the base-rate effect, in certain situations it may be more efficient to focus on identifying potential invaders from amongst already naturalized species than from amongst species at the importation stage.
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  • 83
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    Natural resources research 8 (1999), S. 111-122 
    ISSN: 1573-8981
    Keywords: Risk ; mineral exploration ; decision-making ; mineral economics ; mineral resources ; risk assessment ; Bayes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Successful mineral exploration strategy requires identification of some of the risk sources and considering them in the decision-making process so that controllable risk can be reduced. Risk is defined as chance of failure or loss. Exploration is an economic activity involving risk and uncertainty, so risk also must be defined in an economic context. Risk reduction can be addressed in three fundamental ways: (1) increasing the number of examinations; (2) increasing success probabilities; and (3) changing success probabilities per test by learning. These provide the framework for examining exploration risk. First, the number of prospects examined is increased, such as by joint venturing, thereby reducing chance of gambler's ruin. Second, success probability is increased by exploring for deposit types more likely to be economic, such as those with a high proportion of world-class deposits. For example, in looking for 100+ ton (〉3 million oz) Au deposits, porphyry Cu-Au, or epithermal quartz alunite Au types require examining fewer deposits than Comstock epithermal vein and most other deposit types. For porphyry copper exploration, a strong positive relationship between area of sulfide minerals and deposits' contained Cu can be used to reduce exploration risk by only examining large sulfide systems. In some situations, success probabilities can be increased by examining certain geologic environments. Only 8% of kuroko massive sulfide deposits are world class, but success chances can be increased to about 15% by looking in settings containing sediments and rhyolitic rocks. It is possible to reduce risk of loss during mining by sequentially developing and expanding a mine—thus reducing capital exposed at early stages and reducing present value of risked capital. Because this strategy is easier to apply in some deposit types than in others, the strategy can affect deposit types sought. Third, risk is reduced by using prior information and by changing the independence of trials assumption, that is, by learning. Bayes' formula is used to change the probability of existence of the deposit sought on the basis of successive exploration stages. Perhaps the most important way to reduce exploration risk is to employ personnel with the appropriate experience and yet who are learning.
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  • 84
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    Hydrobiologia 312 (1995), S. 87-92 
    ISSN: 1573-5117
    Keywords: hazard evaluation ; ecotoxicology ; risk assessment ; Pellston series ; toxicity testing ; ecological hazards
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A series of workshops held in the 1970s and 1980s, beginning at the University of Michigan Biological Station near Pellston, Michigan (and thus called the Pellston Series), focused on identifying the basic tenets of ecological hazard/risk assessment. The purpose of this discussion, produced roughly two decades after the first Pellston workshop, is to examine the impacts of this series on the development of the ecological hazard/risk assessment process, to explore some barriers hindering the development of this process, and suggest some new directions and challenges yet unaddressed by any of the workshop series. Probably the most important factor identified since the series of workshops began is persuasive circumstantial evidence that the learning process proceeds at different rates for individuals and institutions both in the government and private sectors, including academe. Evidence presently available suggests that individuals are frequently two or three decades ahead of institutions, and some individuals have already rejected paradigms generally accepted by the profession and are developing new ones. The major contribution of the workshops to the profession was connecting toxicity with environmental fate and transformation of chemicals and thus, bioavailability. Astonishingly, before the first Pellston workshop, this now-obvious connection did not play a dominant role in the peer-reviewed professional literature or in government documents, although the indefatigable investigator could find some minor indications that some professionals were aware of the importance of these relationships. Major suggestions for new directions and challenges focus on: (1) an emphasis on ecosystem health or condition rather than on mere absence of deleterious effects; (2) entering the information age requires that the type of information discussed here be integrated with and related to the broader array of other types of information used in making decisions at the societal or system level — failure to do so will mean that hazard/risk information will have little or no impact; (3) restoration ecology must emerge as a field of considerable importance because inevitably some estimates of hazard/risk will be inaccurate and damage will be done to ecosystems, which must then be repaired; (4) for all of this to function, environmental literacy must be markedly improved over its present level.
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  • 85
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    Hydrobiologia 321 (1996), S. 35-45 
    ISSN: 1573-5117
    Keywords: mercury ; methylmercury ; sediments ; seasonality ; mercury resistant bacteria colonies ; broads
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The environmental factors governing the distribution and behaviour of total and methylmercury within mercury contaminated shallow lakes, associated with the River Yare, Norfolk, UK, have been assessed in situ through the use of sediment cores. These were analysed for microbial and chemical changes on both a temporal and spatial scale. The distribution of total mercury proved to be site dependent and related to the hydrology, sediment transport dynamics, the degree of sediment disturbance and distance from the contamination source. The core profiles revealed a subsurface peak in total mercury with maximum concentrations residing at depths of 12 and 36 cm, depending upon location, with enrichment extending down to depths in excess of 88 cm. This vertical distribution was deemed to reflect historical emission in the late 1960s and early 1970s rather than post depositional migration effects. The distribution of methylmercury was distinct from that of its inorganic counterpart since it also displayed temporal variability with highest concentrations occurring in the spring and summer. Maximum concentrations also prevailed in the uppermost 12 cm of sediment, with peak loadings at or just below the sediment/water interface and detectable levels being restricted to the upper 36 cm. The temporal and spatial behaviour of methylmercury appeared to reflect variations in redox potential, the availability of the Hg2+ ion and the nature of microbial populations.
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  • 86
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    Mathematical geology 31 (1999), S. 471-485 
    ISSN: 1573-8868
    Keywords: recoverable reserves ; conditional simulations ; Monte Carlo simulations ; risk assessment ; gold
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract The aim of this paper is to present a fast method based on bootstrapping, for simulating recoverable reserves for input to financial Monte Carlo simulations. In mining, the three parameters defining recoverable reserves are the cutoff grade, z, the ore tonnage above cutoff, T, and the metal quantity above cutoff, Q. After introducing the concept of 3-dimensional QTz curves, the statistical technique called bootstrapping is reviewed and applied to a set of South African gold grades. As selective mining is carried out on blocks not points, these curves have to be calculated for blocks. The QTz curves obtained by bootstrapping are compared to those obtained by conditionally simulating the same deposit. The procedure has been extended to incorporate geologists' ideas of the likely size of the ore volume. Lastly, the recoverable reserves obtained by bootstrapping are compared with those obtained by traditional risk analysis (base case ± 10% or 20%).
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  • 87
    ISSN: 1573-904X
    Keywords: percutaneous absorption ; stratum corneum ; risk assessment ; volatile solvents ; ATR-FTIR ; acetone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. Simple, safe and quick in vivo methods for estimating chemical uptake into the stratum corneum (SC) from volatile and non-volatile solvents are invaluable to health risk assessors. This study compares the human in vivo SC uptake of a model compound (4-cyanophenol) from water and acetone using quantitative attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. Methods. Small areas on the ventral forearms of human volunteers were treated with 4-cyanophenol (CP) dissolved either in water or acetone. After the skin was cleansed of remaining surface CP, SC samples were taken by a standard tape-stripping method. CP concentration profiles across the SC were quantitated by direct measurement of the permeant on the individual tape-strips using ATR-FTIR. Results. Increasing the duration of exposure to CP aqueous solutions resulted in increasing CP uptake into the SC; the kinetics of uptake correlated well with predictive diffusion equations. Increasing the 'dose' of CP in acetone also resulted in increasing uptake into the SC, but uptake eventually plateaued at a maximum level. The amount of CP taken up into the SC from acetone was 2 to 8-fold greater than that from water following similar short-time exposures. Conclusions. These safe, simple experimental methods provide practical and predictive assessments of chemical uptake into human SC in vivo.
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  • 88
    ISSN: 1573-5060
    Keywords: Beta vulgaris ; BNYVV ; herbicide resistance ; overwintering ; risk assessment ; sugar beet ; transgenic plants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The potential impact of transgenic crops on community ecology will depend on the distribution and establishment of the new transgenic traits, on the sexual transfer of their new genes to the environment (Bartsch & Pohl-Orf, 1996) and on the potential ecological impact of the transgenic trait. Flowering and pollen dispersal is important for outcrossing of the genetically engineered trait. For a biennial plant, like the cultivars of Beta vulgaris L., overwintering is normally necessary to become generative and to produce pollen and seeds (Abe et al., 1997), which usually does not happen with sugar beet as a field crop harvested in autumn (Longden 1989). The starting point for the project was a transgenic sugar beet, Beta vulgaris L. subsp. vulgaris (Lange et al., 1998), with rhizomania and herbicide ( Basta®, Liberty®) resistance. Cold tolerance is one of the most important factors for survival of sugar beet in Central- and North-Europe. Among other ways, spreading of transgenic traits into weed beet (Boudry et al., 1993) or wild beet can occur if genetically engineered – biennial – plants survive the winter, flower in spring and spread their pollen. Field experiments were performed with transgenic breeding lines and their hybrids, transgenic and non-transgenic hybrids with Swiss chard and three conventional beet cultivars to evaluate winter survival rates at seven different field sites. We could show that survival of sugar beet – transgenic as well as conventional ones – in Germany and at the Dutch border is possible. Survival rates were well correlated with temperature data and were unexpectedly high. Differences between sugar beet hybrids and breeding lines could be detected but not within different breeding lines or hybrids. There were no differences detectable between transgenic and non-transgenic plants. The data are crucial for the risk assessment of the release of transgenic sugar beet and are the basis for further experiments towards outcrossing and establishment.
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  • 89
    ISSN: 1573-5060
    Keywords: Beta vulgaris ; BNYVV ; herbicide resistance ; hybridization ; risk assessment ; transgenic plants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary An increasing number of genetically engineered cultivars of several crops is being experimentally released into the environment. In future, crops with new transgenic traits will probably play an important role in agricultural practice. The long-term effect of transgenes on community ecology will depend on the distribution and establishment of transgenic plants in the wild, on the sexual transfer of their new genes to the environment and on the potential ecological impact of the transgenic trait. The starting point was the use of transgenic sugar beet lines, Beta vulgaris subspec. vulgaris var. altissima DÖLL (Helm 1957), with transgenes coding for rhizomania and herbicide (BASTA®) resistance. The first two questions to answer were: Can the transgenes be transferred via pollen to wild beets, Beta vulgaris subspec. maritima (L.) ARCANG. or cultivated relatives such as red beet or spinach beet and are they expressed in the hybrids? Can transgenes be monitored in young Beta vulgaris-hybrids? The experimental transfer of transgenes was conducted in 1993 at a field location in northern Germany. The beets were hand-pollinated with transgenic pollen. In a non destructive biotest, the hybrid seedlings were tested for herbicide resistance. Transgenic plants showed no noxious phenotypic effects whereas control plants developed leaf necroses. All herbicide resistant hybrids within the biotest were assumed to be transgenic.
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  • 90
    ISSN: 1573-5036
    Keywords: mercury ; plant-uptake ; selenite ; selenate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Pot culture experiments containing sand and soil, at two levels of mercury (2 and 5 μg mL-1) added through irrigation with increasing supplementation of selenium (selenite and selenate) led to a decrease in the uptake of mercury by tomato (Lycopersicum esculentum) plant. Both the forms of selenium (selenite and selenate) were found to be equally effective in reducing the mercury accumulation by plants. The observed reduction pattern of mercury accumulation in plant tissues has been discussed on the basis of the formation of insoluble HgSe complex in soil-root environment.
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  • 91
    ISSN: 1573-5095
    Keywords: forest ; risk assessment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Damage to conifer seedlings caused by the pine weevil, Hylobius abietis, was estimated within eighty-two forest sites in Northern Ireland. A wide range of environmental variables were compared with the variation in damage between study sites using multiple logistic regression. Although 45 explanatory variables were considered only four were identified as significant within the final model. The four variables were the size of the planted area, the age of the planting, whether the majority of seedlings were self-seeded or planted, and if the site had been previously planted or was a newly planted area. The identification of these four variables indicates that it is possible to build a model identifying areas at risk to weevil damage. Further, although three of the factors have been recognised as significant influences on weevil damage for some time, they still remain important variables within British Isles forestry, suggesting that there is further scope for more precise targeting of weevil control measures.
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  • 92
    ISSN: 1573-5141
    Keywords: sediment pollution ; macrozoobenthos ; bioassays ; accumulation ; sediment quality triad ; risk assessment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The quality of sediment was assessed in 46 sites in the delta of the rivers Rhine and Meuse (The Netherlands) by means of physical-chemical analysis, field observations on the macrobenthic community structure, accumulation studies and bioassays using Chironomus riparius, Daphnia magna and Photobacterium phosphoreum. The results of chemical analyses were classified using national criteria for sediment quality. Results of field studies and bioassays were classified using criteria derived from research in reference areas or based on data from literature. Risk assessment was carried out according to the sediment quality triad and by means of multi criteria analysis (MCA). The Triad approach was used to demonstrate causal relations between effects on the macrozoobenthos community structure, effects demonstrated in bioassays and sediment pollution. This was done by making a comparison of sediment contamination levels with toxicity data from literature for the test organisms of the bioassays. Using the MCA method, for each site a numerical value was derived for total environmental risk in the present situation, based on observed effects. In this way, a relative risk ranking of all sites was realized. The MCA values for the present situation were also compared with MCA scores based on estimated risks after remediation in 1995, in order to set priorities for sites where remediation is expected to cause a significant reduction in environmental risk. In most of the 46 sites studied so far, the macrofauna community was poorly developed, judged by a low number of benthic species, low abundances and a high dominance of species regarded as relatively tolerant to chemical pollution. In bioassays high sediment toxicity was demonstrated for 24 sites. Using the sediment quality triad approach, 25 sites were identified as areas where pollution can be held responsible for the effects observed in the field. From a comparison of contaminant concentrations in different types of food with maximum tolerable risk levels, and the application of a bioaccumulation model it was concluded that the sediment pollution also implies high risks for plant-, benthos- or fish-eating birds (secondary poisoning of top predators). In the Nieuwe Merwede highest MCA risk scores were found for shallow parts where highly polluted sediments are found. It is concluded that the sediment quality triad and the MCA provide additional information which can be used to establish priorities for remedial action. Based on an ecotoxicological evaluation of the improved quality of new sediments that will be deposited after removal of the polluted sediments in the Nieuwe Merwede, it is concluded that in this upstream part of the Rhine delta remedial action will be effective.
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  • 93
    ISSN: 1573-515X
    Keywords: mercury ; methylmercury ; sulfate reduction ; sulfide ; wetlands
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Methylmercury (MeHg) concentrations and production rates were examined along with sulfur biogeochemistry in Everglades sediments in March, July and December, 1995, as part of a large, multi-investigator study, the Aquatic Cycling of Mercury in the Everglades (ACME) project. The sites examined constitute a trophic gradient, generated from agricultural runoff, across the Everglades Nutrient Removal (ENR) Area, which is a re-constructed wetland, and Water Conservation Areas (WCA) 2A, 2B and 3 in the northern Everglades. MeHg concentrations and %MeHg (MeHg as a percent of total Hg) were lowest in the more eutrophic areas and highest in the more pristine areas in the south. MeHg concentrations ranged from 〈0.1 ng gdw-1 sediment in the ENR to 5 ng gdw-1 in WCA3 sediments; and MeHg constituted 〈0.2% of total Hg (HgT) in ENR, but up to about 2% in two sites in WCA2B and WCA3. Methylation rates in surficial sediments, estimated using tracer-level injections of203 Hg(II) into intact sediment cores, ranged from 0 to 0.12 d-1, or about 1 to 10 ng g-1 d-1when the per day values are multiplied by the ambient total Hg concentration. Methylation was generally maximal at or within centimeters of the sediment surface, and was never observed in water overlying cores. The spatial pattern of MeHg production generally matched that of MeHg concentration. The coincident distributions of MeHg and its production suggest that in situ production controls concentration, and that MeHg concentration can be used as an analog for MeHg production. In addition, the spatial pattern of MeHg in Everglades sediments matches that in biota, suggesting that MeHg bioaccumulation may be predominantly a function of the de novo methylation rate in surficial sediments. Sulfate concentrations in surficial pore waters (up to 400 µm), microbial sulfate-reduction rates (up to 800 nm cc-1 d-1) and resultant pore water sulfide concentrations (up to 300 µm) at the eutrophic northern sites were all high relative to most freshwater systems. All declined to the south, and sulfate concentrations in WCA2B and in central WCA3 resembled those in oligotrophic lakes (50–100 µm). MeHg concentration and production were inversely related to sulfate reduction rate and pore water sulfide. Control of MeHg production in the northern Everglades appears to mimic that in an estuary, where sulfate concentrations are high and where sulfide produced by microbial sulfate reduction inhibits MeHg production.
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  • 94
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    Biogeochemistry 40 (1998), S. 279-291 
    ISSN: 1573-515X
    Keywords: mercury ; methylmercury ; rivers ; sewage ; suspended sediments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The purpose of this study was to investigate the effect of sewage treatment on total mercury (THg) and methylmercury (MeHg) concentrations in domestic effluents and the contribution of urban sewage treatment facilities to THg and MeHg in rivers. We determined the concentrations of THg and MeHg in unfiltered samples of untreated and treated domestic sewage from the three treatment facilities and receiving river water within the City of Winnipeg. The concentrations of THg in the Red and Assiniboine rivers ranged from 3–31 ng/L. THg was related positively to suspended sediment concentrations in the rivers. The concentrations of MeHg in these rivers were usually 0.2–0.3 ng/L. THg concentrations in raw sewage varied widely, from 2–150 ng/L. Treatment removed an average of 88% of this mercury. MeHg concentrations in raw sewage were 0.5–4.3 ng/L, however, after treatment at two treatment facilities, MeHg was greatly reduced, usually to 0.1–0.4 ng/L. Most treated sewage, therefore, had MeHg concentrations that were similar to levels in the receiving rivers and the effect of discharged effluent was usually a change of about 2% or less on concentrations in the rivers. However, one of the facilities (the West End plant) was discharging higher concentrations of MeHg, up to 2 ng/L, causing calculated increases of up to 11% in the concentration of MeHg in the Assiniboine River.
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  • 95
    ISSN: 1573-515X
    Keywords: atmospheric deposition ; catchment output ; Fenno-Scandia ; mercury cycling ; methylmercury ; mercury
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The input and output flux data of total Hg (THg) and methylmercury (MeHg) from three catchments located in different geographical regions in Sweden and one catchment in southern Finland were compared to elucidate the role of current atmospheric Hg/MeHg deposition with regard to waterborne Hg/MeHg output. There was a negative co-variaton between the open field THg inputs and the ratio of THg output to open field input. The highest ratio (and lowest input) occurring in N. Sweden and S. Finland, while the lowest output ratio (and highest inputs) occurred in southwest Sweden. A much larger variation was found in the ratio of output to open field input for MeHg (14 to 160%). Examinations of MeHg input/output data in relation to catchment charateristics suggest that riparian peat, mires and wet organic soil contributed to the large MeHg output from certain catchments, probably due to in situ production of MeHg. This finding is consistent with other studies which have found that catchment characteristics such as wetland area, flow pathways, seasonal temperature and water flow are important in controlling the output of MeHg. These catchment characteristics govern the fate of the contemporary input of Hg and MeHg as well as the mobilization of the soil pools.
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  • 96
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    Biogeochemistry 40 (1998), S. 235-247 
    ISSN: 1573-515X
    Keywords: fish ; invertebrates ; ligands ; mercury ; methylmercury ; phytoplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract To understand the accumulation of inorganic mercury and methylmercury at the base of the estuarine food chain, phytoplankton (Thalassiosira weissflogii) uptake and mercury speciation experiments were conducted. Complexation of methylmercury as methylmercury-bisulfide decreased the phytoplankton uptake rate while the uptake rate of the methylmercury-cysteine and -thiourea complexes increased with increasing complexation by these ligands. Furthermore, our results indicated that while different ligands influenced inorganic mercury/methylmercury uptake by phytoplankton cells, the ligand complex had no major influence on either where the mercury was sequestered within the phytoplankton cell nor the assimilation efficiency of the mercury by copepods. The assimilation efficiency of inorganic mercury/methylmercury by copepods and amphipods feeding on algal cells was compared and both organisms assimilated methylmercury much more efficiently; the relative assimilation efficiency of methylmercury to inorganic mercury was 2.0 for copepods and 2.8 for amphipods. The relative assimilation is somewhat concentration dependent as experiments showed that as exposure concentration increased, a greater percentage of methylmercury was found in the cytoplasm of phytoplankton cells, resulting in a higher concentration in the copepods feeding on these cells. Additionally, food quality influenced assimilation by invertebrates. During decay of a T. weissflogii culture, which served as food for the invertebrates, copepods were increasingly less able to assimilate the methylmercury from the food, while even at advanced stages of decay, amphipods were able to assimilate mercury from their food to a high degree. Finally, fish feeding on copepods assimilated methylmercury more efficiently than inorganic mercury owing to the larger fraction of methylmercury found in the soft tissues of the copepods.
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  • 97
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    Biogeochemistry 40 (1998), S. 115-123 
    ISSN: 1573-515X
    Keywords: CVAFS ; foliage ; mercury ; microwave digestion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract A microwave technique for digesting foliage samples was developed and evaluated for quantifying low levels of Hg by cold vapor atomic fluorescence spectroscopy, CVAFS. The method meets three criteria: (1) to digest all sample material completely and consistently, (2) to reduce sample digestion time to less than one hour, and (3) to maintain a low analytical blank. Mean recovery of NIST standards was 90±6%. Samples that were analyzed by this technique and by Instrumental Neutron Activation Analysis compared within 15%. This method also compared within 15% of hot acid digestion methods on samples prepared and analyzed by CVAFS at different laboratories in the First International Mercury in Foliage Intercomparison of Methods (FIM)2. The largest source of variability in all of the interlaboratory comparisons was sample inhomogeneity rather than analytical error.
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  • 98
    ISSN: 1573-5117
    Keywords: mercury ; contamination ; water-sediment ; bacteria ; resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In Brazil mercury is used indiscriminately at prospecting sites for gold extraction, with a consequent enormous discharge of this metal into the aquatic ecosystem. Mercury concentration was investigated in 1995, 1996 and 1997 in the sediments of ten sites along the Carmo stream, MG, Brazil, almost all of them located in prospecting areas. Analysis of mercury in the sediments of all sampling sites showed that the levels were above the tolerable limit (0.1μg g−1), except for sites P4 (1997), P6 (1995) and P9 (1995 and 1997). The results showed wide mercury contamination in an environment not limited to the active or inactive prospecting areas, but also including sites outside these areas but downstream from them. There was a high incidence of bacteria resistant to mercury in the aquatic communities of the sites under study, ranging from 27.3 to 77.1%, except for P1 (an ecological station upstream from the sites under study) in which all bacteria isolated from water were sensitive. Furthermore, the fall in mercury concentration in the sediment at site P5 was not as marked as at other sites, with a frequency of resistant bacteria of only 27.3%, possibly indicating a slower detoxification. The statistical analysis (Pearson’s correlation = − 0,527) showed that the hypothesis about negative correlation between the incidence of bacterial resistance and the total mercury concentration in this environment is supported. Hence, all these data denote a moderate association between the distribution of resistant bacteria and the presence of mercury compounds.
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  • 99
    ISSN: 1573-515X
    Keywords: binary variables ; fish ; impoundment ; indicator variables ; James Bay ; mercury ; polynomial regression ; Québec ; reservoirs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Mercury levels in fish in reservoirs and natural lakes have been monitored on a regular basis since 1978 at the La Grande hydroelectric complex located in the James Bay region of Québec, Canada. The main analytical tools historically used were analysis of covariance (ANCOVA), linear regression of the mercury-to-length relationship and Student-Newman-Keuls (SNK) multiple comparisons of mean mercury levels. Inadequacy of linear regression (mercury-to-length relationships are often curvilinear) and difficulties in comparing mean mercury levels when regressions differ lead us to use polynomial regression with indicator variables. For comparisons between years, polynomial regression models relate mercury levels to length (L), length squared (L2), binary (dummy) indicator variables (Bn), each representing a sampled year, and the products of each of these explanatory variables (L × B1, L2 × B1, L × B2, etc.). Optimal transformations of the mercury levels (for normality and homogeneity) were found by the Box-Cox procedure. The models so obtained formed a partially nested series corresponding to four situations: (a) all years are well represented by a single polynomial model; (b) the year-models are of the same shape, but the means may differ; (c) the means are the same, but the year-models differ in shape; (d) both the means and shapes may differ among years. Since year-specific models came from the general one, rigorous statistical comparisons are possible between models. Polynomial regression with indicator variables allows rigorous statistical comparisons of mercury-to-length relationships among years, even when the shape of the relationships differ. It is simple to obtain accurate estimates of mercury levels at standardized length, and multiple comparisons of these estimations are simple to perform. The method can also be applied to spatial analysis (comparison of sampling stations), or to the comparison of different biological forms of the same species (dwarf and normal lake whitefish).
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  • 100
    ISSN: 1573-515X
    Keywords: atmospheric deposition ; beaver impoundment ; mercury ; methylmercury ; wetlands
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The biogeochemistry of Hg was evaluated in a small wetland in the Adirondack region of New York. Concentrations of total Hg (HgT) in streamwater draining the wetland showed little temporal variation. The annual areal watershed flux of HgT (2.2 µg/m2-yr) was considerably smaller than regional inputs of atmospheric deposition of HgT, indicating that the terrestrial environment is a net sink for atmospheric deposition of HgT. Drainage inputs of HgT were conservatively transported through the beaver impoundment. The annual flux of total methyl mercury (CH3Hg+ T was greater than literature values of atmospheric deposition suggesting that the watershed is a net source of CH3Hg+ T . Stream concentrations of CH3Hg+ T increased during low-flow summer conditions in a riparian wetland, and particularly at the outlet of the beaver impoundment. Net production of CH3Hg+ T occurred in the beaver impoundment (0.45 µg/m2-yr). Rates of net methylation for the beaver impoundment were comparable to values reported in the literature for wetlands.
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