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Doi: 10.1080/10473289.2011.599281 The objective of this study was to estimate the contribution of a facility that processes steel production slag into raw material for cement production to local outdoor particle [...]

In the current U.S. Environmental Protection Agency reference dose (RfD) for methytmercury, the one-compartment pharmacokinetic model is used to convert fetal cord blood mercury (Hg) concentration to a maternal intake [...]

Abstract Background Toenail-Hg levels are being used as a marker of methylmercury (MeHg) exposure in efforts to associate exposure with effects such as cardiovascular disease. There is a need to correlate this marker with more established biomarkers that presently underlie existing dose–response relationships in order to compare these relationships across studies. Methods As part of the Arsenic Mercury Intake Biometric Study, toenail clippings were collected at three time points over a period of one year amongst females from within the population of Japanese living near Puget Sound in Washington State (US). Variability in temporal intra-individual toenail-Hg levels was examined and chronologically matched hair and toenail samples were compared to more accurately define the toxicokinetic variability of Hg levels observed between the two compartments. Results Mean toenail-Hg values (n=43) for the 1st, 2nd and 3rd visits were 0.60, 0.60 and 0.56 ng/mg. Correlations were as follows: r=0.92 between 1st and 2nd clinic visits, r=0.75 between 1st and 3rd visits and r=0.87 between 2nd and 3rd visits. With few exceptions, toenail-Hg values from any visit were within 50-150% of the individual’s mean toenail-Hg level. Nearly all participants had less than a two-fold change in toenail-Hg levels across the study period. A regression model of the relationship between toenail-Hg and hair-Hg (n = 41) levels representing the same time period of exposure, gave a slope (Hg ng/mg) of 2.79 for hair relative to toenail (r=0.954). Conclusions A chronologically matched hair-Hg to toenail-Hg ratio has been identified within a population that consumes fish regularly and in quantity. Intra-individual variation in toenail-Hg levels was less than two-fold and may represent dietary-based fluctuations in body burden for individuals consuming various fish species with different contaminant levels. The chronologically matched ratio will be useful for relating MeHg exposure and dose–response derived from toenail-Hg measurements to those derived from hair-Hg measurements in other studies, and may be useful in future investigations as an indicator of stable MeHg body burden within a population.

Abstract Background The most prominent non-occupational source of exposure to methylmercury is the consumption of fish. In this study we examine a fish consuming population to determine the extent of temporal exposure and investigate the extent to which single time estimates of methylmercury exposure based on blood-Hg concentration can provide reliable estimates of longer-term average exposure. Methods Blood-mercury levels were obtained from a portion of the Arsenic Mercury Intake Biometric Study (AMIBS) cohort. Specifically, 56 Japanese women residing in the Puget Sound area of Washington State, US were sampled on three occasions across a one-year period. Results An average of 135 days separated samples, with mean blood-mercury levels for the visits being 5.1, 6.6 and 5.0 μg/l and geometric means being 2.7, 4.5 and 3.1 μg/l. The blood-mercury levels in this group exceed national averages with geometric means for two of the visits being between the 90th and 95th percentiles of nationally observed levels and the lowest geometric mean being between the 75th and 90th percentile. Group means were not significantly different across sampling periods suggesting that exposure of combined subjects remained relatively constant. Comparing intra-individual results over time did not reveal a strong correlation among visits (r = 0.19, 0.50, 0.63 between 1st and 2nd, 2nd and 3rd, and 1st and 3rd sample results, respectively). In comparing blood-mercury levels across two sampling interval combinations (1st and 2nd, 2nd and 3rd, and 1st and 3rd visits, respectively), 58% (n = 34), 53% (n = 31) and 29% (n = 17) of the individuals had at least a 100% difference in blood-Hg levels. Conclusions Point estimates of blood-mercury, when compared with three sample averages, may not reflect temporal variability and individual exposures estimated on the basis of single blood samples should be treated with caution as indicators of long-term exposure. Reliance on single blood samples can make predicting ongoing methylmercury exposure highly speculative due to the large intra-individual variability.

Abstract Historically, concerns with fish consumption have addressed risks from contaminants (e.g., methylmercury (MeHg), and PCBs). More recently public health concerns have widened in appreciation of the specific benefits of fish consumption such as those arising from polyunsaturated fatty acids (PUFAs) in fish oil. Fish contains varying levels of PUFAs and MeHg. Since both address the same health outcomes (in opposite directions) and occur together in fish, great care must be exercised in providing public health guidance. Mozaffarian and Rimm in a recent article (JAMA. 2006, 296:1885–99) have made a strong case for the beneficial effects of PUFAs in reducing the risk of coronary heart disease, but at the same time, have also broadly discounted the increased risks of coronary heart disease posed by MeHg in fish, stating that "... among adults... the benefits of fish intake exceed the potential risks." This conclusion appears to be based on an inaccurate and insufficiently critical analysis of the literature. This literature is re-examined in light of their conclusions, and the available and appropriate public health options are considered.

Abstract In 2000, the National Research Council (NRC), an arm of the National Academy of Sciences, released a report entitled, "Toxicological Effects of Methylmercury." The overall conclusion of that report was that, at levels of exposure in some fish- and marine mammal-consuming communities (including those in the Faroe Islands and New Zealand), subtle but significant adverse effects on neuropsychological development were occurring as a result of in utero exposure. Since the release of that report, there has been continuing discussion of the public health relevance of current levels of exposure to Methylmercury. Much of this discussion has been linked to the release of the most recent longitudinal update of the Seychelles Island study. It has recently been posited that these findings supercede those of the NRC committee, and that based on the Seychelles findings, there is little or no risk of adverse neurodevelopmental effects at current levels of exposure. In this commentary, members of the NRC committee address the conclusions from the NRC report in light of the recent Seychelles data. We conclude that no evidence has emerged since the publication of the NRC report that alters the findings of that report.

Golding et al. (2013) described regression analysis of dietary contributions to maternal blood mercury levels, nested within the Avon Longitudinal Study of Parents and Children (ALSPAC). Fish intake explained only [...]

Historically, concerns with fish consumption have addressed risks from contaminants (e.g., methylmercury (MeHg), and PCBs). More recently public health concerns have widened in appreciation of the specific benefits of fish consumption such as those arising from polyunsaturated fatty acids (PUFAs) in fish oil. Fish contains varying levels of PUFAs and MeHg. Since both address the same health outcomes (in opposite directions) and occur together in fish, great care must be exercised in providing public health guidance. Mozaffarian and Rimm in a recent article (JAMA. 2006, 296:1885-99) have made a strong case for the beneficial effects of PUFAs in reducing the risk of coronary heart disease, but at the same time, have also broadly discounted the increased risks of coronary heart disease posed by MeHg in fish, stating that "... among adults... the benefits of fish intake exceed the potential risks." This conclusion appears to be based on an inaccurate and insufficiently critical analysis of the literature. This literature is re-examined in light of their conclusions, and the available and appropriate public health options are considered. [ABSTRACT FROM AUTHOR]

Presents a letter to the editor commenting on benefits of fish consumption.

In 2000, the National Research Council (NRC), an arm of the National Academy of Sciences, released a report entitled, "Toxicological Effects of Methylmercury." The overall conclusion of that report was that, at levels of exposure in some fish- and marine mammal-consuming communities (including those in the Faroe Islands and New Zealand), subtle but significant adverse effects on neuropsychological development were occurring as a result of in utero exposure. Since the release of that report, there has been continuing discussion of the public health relevance of current levels of exposure to Methylmercury. Much of this discussion has been linked to the release of the most recent longitudinal update of the Seychelles Island study. It has recently been posited that these findings supercede those of the NRC committee, and that based on the Seychelles findings, there is little or no risk of adverse neurodevelopmental effects at current levels of exposure. In this commentary, members of the NRC committee address the conclusions from the NRC report in light of the recent Seychelles data. We conclude that no evidence has emerged since the publication of the NRC report that alters the findings of that report. [ABSTRACT FROM AUTHOR]

While default uncertainty factor (UF) adjustments have been proposed for pharmacokinetic variability in the derivation of Reference Doses (RfDs), few attempts have been made to derive chemical-specific UFs for such variability. In recent epidemiologic data on the neuro-developmental effects of MeHg, Hg concentration in either hair or blood is the point-of-departure for RfD derivation. The application of a pharmacokinetic model to derive an intake dose from the measured biomarker concentration allows examination of the inter-individual variability in the relationship between intake dose and biomarker concentration through specification of the variability in model parameters. Three independent studies of this variability, using different models and/or different parameter values, are compared. While differences in central tendency estimates give different predictions of the intake dose corresponding to a given biomarker concentration, normalization of the central tendency estimate resulted in strong agreement among the studies. Starting with Hg concentration in hair or blood, and dividing a central tendency estimate of the corresponding intake dose by a UF of 2 to 3, accounts for 95 to 99% of the variability in the relationship between intake dose and biomarker concentration. This variability, however, encompasses only a portion of the maternal ingestion-to-fetal brain pathway. It is therefore likely that this UF underestimates the overall pharmacokinetic variability in this pathway. [ABSTRACT FROM AUTHOR]

The increase in systolic blood pressure in males appears to be the most sensitive adult endpoint appropriate for deriving a health risk-based target level of lead (Pb) in soil. Because the response of blood pressure to blood Pb concentration (PbB) has no apparent threshold, traditional approaches based on the application of a Reference Dose (RfD) are not applicable. An alternative approach is presented based on a model which predicts the population shift in systolic blood pressure from ingestion of Pb contaminated soil as a simultaneous function of exposure to Pb in soil, the baseline distribution of blood Pb concentration in the population and the baseline distribution of systolic pressure in the population. This model is analyzed using Monte Carlo analysis to predict the population distribution of systolic pressure resulting from Pb exposure. Based on this analysis, it is predicted that for adult males 18-65 years old, exposure to 1000 ppm Pb in soil will result in an increase of approximately 1 mm Hg systolic pressure, an increase in the incidence of systolic hypertension (i.e., systolic pressure >140 mm Hg) of approximately 1% and an increase in PbB of 1-3 µg/dl. Based on the proposition that these adverse effects can be considered de minimis, 1000 ppm Pb in soil is proposed as a target soil concentration for adult exposure. Available data do not appear to be adequate to predict the newborn PbB level which would result from exposure to this soil level during pregnancy. [ABSTRACT FROM AUTHOR]

Inability to define either a clear toxicologic threshold or a stochastic all-or-nothing (cancer-type) response model for the noncarcinogenic effects of lead (Pb) in young children has posed difficulties for derivation of risk-based target levels of Pb in residential soil. Approaches based on empirical relationships between Pb levels in blood (PbB) and Pb in soil suffer from inability to specify the numerous variables which mediate between these two quantities. Approaches based on achieving a toxicologically de minimis target PbB level (e.g., 10 µg/dl) are subject to large uncertainty in estimating the distribution of existing PbB levels in a specific exposed population and in estimating the relative contribution from nonsoil sources of Pb. The multisource contribution to the distribution of PbB makes this approach unsuited for determination of a target Pb level in a single medium. An alternative approach is presented based on achieving a de minimis contribution to PbB (ΔPbB) from soil. Contributions to Pb exposure from outdoor soil and indoor soil-derived dust (ISDD) are modeled and appropriate values are suggested for input parameters. This analysis predicts that chronic exposure of young children to 200 µg Pb/g (ppm) in residential soil will result in a ΔPbB of 2 µg Pb/dl blood. This concentration of Pb in soil may provide an appropriate target level for residential soil when other significant sources of Pb exposure are present. In other eases, this approach can be used to predict a soil concentration of Pb corresponding to an appropriate non-de minimis ΔPbB. [ABSTRACT FROM AUTHOR]

Presents a letter to the editor in response to the article "Urinary Excretion of Chromium Following Ingestion of Chromite-Ore Processing Residues in Humans: Implications for Biomonitoring," by M.L. Gargas in the October 1994 issue of the periodical "Risk Analysis."

The recent article by Costa and Klein (2006) contains several inaccuracies about the federal drinking water standard for chromium. The federal drinking water standard for chromium is 100 ppb, not 50 ppb as stated by Costa and Klein, and it is based on non-carcinogenic effects, not a one in one million cancer risk level. The question of whether or not hexavalent chromium is carcinogenic via the oral route is the focus of much current interest and has major implications for regulation of chromium in drinking water and soil. The chronic drinking water study of hexavalent chromium currently being conducted by the National Toxicology Program will provide further information that will be useful in addressing this question. [ABSTRACT FROM AUTHOR]