Chronologically matched toenail-Hg to hair-Hg ratio: temporal analysis within the Japanese community (U.S.).

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.

Single blood-Hg samples can result in exposure misclassification: temporal monitoring within the Japanese community (United States).

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.

Which fish should I eat? Perspectives influencing fish consumption choices.

BACKGROUND: Diverse perspectives have influenced fish consumption choices. OBJECTIVES: We summarized the issue of fish consumption choice from toxicological, nutritional, ecological, and economic points of view; identified areas of overlap and disagreement among these viewpoints; and reviewed effects of previous fish consumption advisories. METHODS: We reviewed published scientific literature, public health guidelines, and advisories related to fish consumption, focusing on advisories targeted at U.S. populations. However, our conclusions apply to groups having similar fish consumption patterns. DISCUSSION: There are many possible combinations of matters related to fish consumption, but few, if any, fish consumption patterns optimize all domains. Fish provides a rich source of protein and other nutrients, but because of contamination by methylmercury and other toxicants, higher fish intake often leads to greater toxicant exposure. Furthermore, stocks of wild fish are not adequate to meet the nutrient demands of the growing world population, and fish consumption choices also have a broad economic impact on the fishing industry. Most guidance does not account for ecological and economic impacts of different fish consumption choices. CONCLUSION: Despite the relative lack of information integrating the health, ecological, and economic impacts of different fish choices, clear and simple guidance is necessary to effect desired changes. Thus, more comprehensive advice can be developed to describe the multiple impacts of fish consumption. In addition, policy and fishery management interventions will be necessary to ensure long-term availability of fish as an important source of human nutrition.

Balancing the benefits of n-3 polyunsaturated fatty acids and the risks of methylmercury exposure from fish consumption.

Fish and shellfish are widely available foods that provide important nutrients, particularly n-3 polyunsaturated fatty acids (n-3 PUFAs), to many populations globally. These nutrients, especially docosahexaenoic acid, confer benefits to brain and visual system development in infants and reduce risks of certain forms of heart disease in adults. However, fish and shellfish can also be a major source of methylmercury (MeHg), a known neurotoxicant that is particularly harmful to fetal brain development. This review documents the latest knowledge on the risks and benefits of seafood consumption for perinatal development of infants. It is possible to choose fish species that are both high in n-3 PUFAs and low in MeHg. A framework for providing dietary advice for women of childbearing age on how to maximize the dietary intake of n-3 PUFAs while minimizing MeHg exposures is suggested.

Evaluation of the cardiovascular effects of methylmercury exposures: current evidence supports development of a dose-response function for regulatory benefits analysis.

BACKGROUND: The U.S. Environmental Protection Agency (U.S. EPA) has estimated the neurological benefits of reductions in prenatal methylmercury (MeHg) exposure in past assessments of rules controlling mercury (Hg) emissions. A growing body of evidence suggests that MeHg exposure can also lead to increased risks of adverse cardiovascular impacts in exposed populations. DATA EXTRACTION: The U.S. EPA assembled the authors of this article to participate in a workshop, where we reviewed the current science concerning cardiovascular health effects of MeHg exposure via fish and seafood consumption and provided recommendations concerning whether cardiovascular health effects should be included in future Hg regulatory impact analyses. DATA SYNTHESIS: We found the body of evidence exploring the link between MeHg and acute myocardial infarction (MI) to be sufficiently strong to support its inclusion in future benefits analyses, based both on direct epidemiological evidence of an MeHg-MI link and on MeHg's association with intermediary impacts that contribute to MI risk. Although additional research in this area would be beneficial to further clarify key characteristics of this relationship and the biological mechanisms that underlie it, we consider the current epidemiological literature sufficiently robust to support the development of a dose- response function. CONCLUSIONS: We recommend the development of a dose- response function relating MeHg exposures with MIs for use in regulatory benefits analyses of future rules targeting Hg air emissions.

Arsenic exposure within the Korean community (United States) based on dietary behavior and arsenic levels in hair, urine, air, and water.

BACKGROUND: Determining arsenic exposure in groups based on geographic location, dietary behaviors, or lifestyles is important, as even moderate exposures may lead to health concerns. OBJECTIVES/METHODS: The Korean community in Washington State, represents a group warranting investigation, as they consume foods (e.g., shellfish, rice, finfish, and seaweed) known to contain arsenic. As part of the Arsenic Mercury Intake Biometric Study, we examined the arsenic levels in hair and urine along with the diets of 108 women of childbearing age from within this community. Arsenic levels in indoor air and drinking water were also investigated, and shellfish commonly consumed were collected and analyzed for total and speciated arsenic. RESULTS: The six shellfish species analyzed (n = 667) contain total arsenic (range, 1-5 microg/g) but are a small source of inorganic arsenic (range, 0.01-0.12 microg/g). Six percent of the individuals may have elevated urinary inorganic arsenic levels (> 10 microg/L) due to diet. Seaweed, rice, shellfish, and finfish are principal sources for total arsenic intake/excretion based on mass balance estimates. Rice consumption (163 g/person/day) may be a significant source of inorganic arsenic. Air and water are not significant sources of exposure. Hair is a poor biometric for examining arsenic levels at low to moderate exposures. CONCLUSIONS: We conclude that a portion of this community may have dietary inorganic arsenic exposure resulting in urine levels exceeding 10 microg/L. Although their exposure is below that associated with populations exposed to high levels of arsenic from drinking water (> 100 microg/L), their exposure may be among the highest in the United States.

Longitudinal mercury monitoring within the Japanese and Korean communities (United States): implications for exposure determination and public health protection.

BACKGROUND: Estimates of exposure to toxicants are predominantly obtained from single time-point data. Fish consumption guidance based on these data may be incomplete, as recommendations are unlikely to consider impact from factors such as intraindividual variability, seasonal differences in consumption behavior, and species consumed. OBJECTIVES/METHODS: We studied populations of Korean (n = 108) and Japanese (n = 106) women living in the Puget Sound area in Washington State to estimate mercury exposure based on fish intake and hair Hg levels at two and three time points, respectively. Our goals were to examine changes in hair Hg levels, fish intake behavior, and Hg body burden over time; and to determine if data from multiple time points could improve guidance. RESULTS/CONCLUSION: More than 50 fish species were consumed, with eight species representing approximately three-fourths of fish consumed by the Japanese and 10 species representing approximately four-fifths of fish intake by the Koreans. Fish species responsible for most Hg intake did not change over time; < 10 species accounted for most of the Hg body burden in each population. Longitudinal variability of hair Hg levels changed slowly across the study period. Japanese with hair Hg levels > 1.2 ppm (mean, 2.2 ppm) consumed approximately 150% more fish than those with levels < or = 1.2 ppm (mean, 0.7 ppm). However, because many participants consumed substantial amounts of fish while having hair-Hg levels < or = 1.2 ppm, the nutritional benefits offered from fish consumption should be obtainable without exceeding the RfD. We observed a 100% difference in fish intake between open-ended and 2-week recall fish consumption surveys. Open-ended survey data better represent Hg intake as determined from hair Hg levels. Single time-point fish intake data appear to be adequate for deriving guidance, but caution is warranted, as study is required to determine the significance of the different outcomes observed using the two survey time frames.

Fish intake guidelines: incorporating n-3 fatty acid intake and contaminant exposure in the Korean and Japanese communities.

BACKGROUND: Fish consumption advisories are developed to prevent overexposure to various contaminants. Recently, discussion has centered on the need to consider the benefits of fish consumption alongside possible risks when providing guidance. OBJECTIVE: As part of the Arsenic Mercury Intake Biometric Study involving the Japanese and Korean communities living in Washington State, we obtained fish and nutrient intake data. Japanese and Korean women of childbearing age (n = 214) participated in this longitudinal study. We used these data, along with hair-mercury data to determine the need for both the nutritional benefits and concern about contaminants to be included when providing guidance. DESIGN: We examined the intake of 2 n-3 long-chain fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), found in fish and associated with a variety of beneficial health effects. Intakes of these lipids were used as surrogates to characterize the beneficial effect from fish consumption, and the intake of mercury was used to establish the risk from consumption. RESULTS: These 2 populations provided an ideal basis from which to examine this issue because their fish consumption rates were identical and higher than national rates, but their mercury intakes vary substantially because of different consumption behaviors. Results indicate that basing fish consumption guidelines on contaminant concentrations alone can have the unintended consequence of causing a portion of the population to have inadequate intake of required nutrients. CONCLUSION: Public health goals may be better served if nutritional elements and contaminant concerns are quantitatively incorporated into fish consumption guidelines.

Mercury exposure from fish consumption within the Japanese and Korean communities.

Public health guidance pertaining to fish consumption requires that we be cognizant of the health concerns associated with eating contaminated fish and the nutritional benefits obtained from fish consumption. In doing so, a need exists for an improved understanding of the extent of contamination within various fish species consumed by populations of concern and the extent of exposure to contamination by these populations. As part of the Arsenic Mercury Intake Biometric Study involving the Japanese and Korean communities, it was possible to obtain fish intake data, determine mercury (Hg) fish tissue concentrations for various species consumed, and examine hair for Hg levels of study participants. This longitudinal study (n = 214) included 106 Japanese and 108 Korean women of childbearing age. Hair Hg levels for the two populations and weight-normalized, species-specific, individual-consumption pattern data that estimated Hg intake levels were compared with published National Health and Nutrition Examination Survey (NHANES) data. Sensitivity analyses and population-specific probabilistic assessments of exposure were conducted. The estimated Hg intake levels for the Japanese (0.09 microg/kg/d) and Koreans (0.05 microg/kg/d) were above the NHANES estimates (0.02 microg/kg/d), as were the hair Hg levels (1.23, 0.61, 0.2 ppm, respectively). Results indicate that (1) there are significant differences between the fish-species-consumption behavior of these two populations; (2) even when fish-consumption rates are equal between two populations, Hg intakes between them can vary significantly; and (3) these population and Hg intake differences present public health challenges when attempting to provide fish consumption guidance.

An examination of the trade-offs in public health resulting from the use of default exposure assumptions in fish consumption advisories.

Efforts to provide for public health protection from environmental contaminants in fish have resulted in various advisories or recommendations with regard to fish consumption from local, state, and federal agencies. These advisories are based on measured levels of contaminants in fish that are combined with values for body weight and portion size to produce an estimate of an "acceptable" consumption frequency (e.g., eat no more than once per month). Because values for body weight and portion size are generally generic default values, they do not necessarily relate to a specific population or to any individual in that population. Thus, the use of default values may result in underprotection or overprotection in any given case. Given the benefits of fish consumption and the risks from overexposure to various toxicants, vigilance is required by custodians of public health to ensure that populations are protected while being cautious not to over- or underprotect them. In this analysis, we examine the "acceptable" consumption limits derived for fish species/groups consumed by three specific populations and determine the extent of public health protection afforded by these limits. To accomplish this, the "acceptable" consumption frequencies are derived based, in part, on default assumptions and are compared to intakes calculated from empirically derived species-specific individual consumption and demographic data. Sensitivity analyses and population-specific probabilistic assessments of exposure are conducted to identify those values and/or assumptions which might significantly influence the resulting fish consumption advisories. Three populations were chosen for study based on their ability to represent populations of greatest concern: those most sensitive and/or those most exposed. We conclude from this investigation that consumption pattern data, contaminant data and body weight data together can be used to make fish consumption advisories more focused and, therefore, less likely to be under- or overprotective.

The importance of weight-normalized exposure data when issuing fish advisories for protection of public health.

Public health protection from environmental contaminants requires an understanding of the extent of contamination and of the extent of exposure to the contamination. My argument here is that weight-normalized, species-specific, individual-consumption pattern data are vital for determining exposure levels used to ascertain health protection measures and impacts from consuming contaminated fish. This study demonstrates the importance of adequate consumption pattern data for determining exposure distributions used for public health protection by examining three populations exposed to methylmercury through fish consumption: one recreational angler population and two Native-American populations. I compared exposure distributions derived from empirically derived species-specific, individual-consumption data from the three populations and exposure distributions derived, in part, from summary statistics for populations. In so doing, I conducted sensitivity analyses and population-specific probabilistic assessments of exposure. Although the goals of present-day accepted practices--using exposure distributions derived partly from point-estimate-based consumption and body-weight values--are laudable, results presented here indicate that weight-adjusted intake values for a population of concern are warranted when determining exposure distributions and should not be neglected in a health assessment instigated by available data on contaminant concentrations. If individual intake data are unobtainable, raw data from similar populations or tabulated values providing contaminant intake normalized for body weight may be viable alternatives to default values, and can be used to adequately protect public health. Without weight-normalized consumption pattern data to determine exposure, health assessment conclusions can mislead the public and have diminishing protective value.