An Exposure Assessment for Methylmercury from Seafood for Consumers in the United States

Abstract

An exposure model was developed to relate seafood consumption to levels of methylmercury (reported as mercury) in blood and hair in the U.S. population, and two subpopulations defined as children aged 2-5 and women aged 18-45. Seafood consumption was initially modeled using short-term (three-day) U.S.-consumption surveys that recorded the amount of fish eaten per meal. Since longer exposure periods include more eaters with a lower daily mean intake, the consumption distribution was adjusted by broadening the distribution to include more eaters and reducing the distribution mean to keep total population intake constant. The estimate for the total number of eaters was based on long-term purchase diaries. Levels of mercury in canned tuna, swordfish, and shark were based on FDA survey data. The distribution of mercury levels in other species was based on reported mean levels, with the frequency of consumption of each species based on market share. The shape distribution for the given mean was based on the range of variation encountered among shark, tuna, and swordfish. These distributions were integrated with a simulation that estimated average daily intake over a 360-day period, with 10,000 simulated individuals and 1,000 uncertainty iterations. The results of this simulation were then used as an input to a second simulation that modeled levels of mercury in blood and hair. The relationship between dietary intake and blood mercury in a population was modeled from data obtained from a 90-day study with controlled seafood intake. The relationship between blood and hair mercury in a population was modeled from data obtained from several sources. The biomarker simulation employed 2,000 simulated individuals and 1,000 uncertainty iterations. These results were then compared to the recent National Health and Nutrition Examination Survey (NHANES) that tabulated blood and hair mercury levels in a cross-section of the U.S. population. The output of the model and NHANES results were similar for both children and adult women, with predicted mercury biomarker concentrations within a factor of two or less of NHANES biomarker results. However, the model tended to underpredict blood levels for women and overpredict blood and hair levels for children.

Bioaccumulation of trace elements in pelagic fish from the Western Indian Ocean

“…A great deal of publications on marine fish report only Hg levels because this metal is of particular concern for human health (e.g. Carrington and Bolger, 2002;Marcotrigiano and Storelli, 2003;Gochfeld, 2004, 2005;Rasmussen et al, 2006). Inorganic mercury occurring naturally or from pollution is converted to methyl-mercury (MeHg) by microorganisms and is biomagnified up the food chain.…”

Reconstructing population exposures to environmental chemicals from biomarkers: Challenges and opportunities

“…For example, in the case of a long half-life chemical such as methylmercury, it has been illustrated that by merging fish consumption surveys, dietary intake models, and national fish methylmercury data, reasonable agreement between biomarkers and data can be reached (Carrington and Bolger, 2002).…”

Methylmercury, Fish Consumption, and the Precautionary Principle

“…28 Average Exposures to MeHg. At a consumption-weighted average MeHg concentration in fish of 0.15 ppm, 22 a consumption rate of 19 g/day, and a median body weight of 71.4 kg, 4,5 the corresponding population-average MeHg exposure rate would be ϳ0.039 g/kg/day, which is below the EPA-recommended limit of 0.1 g/kg/day. This estimate is also consistent with the data of Stern et al…”

“…These rates are consistent with a previous analysis. 4,5 However, although a recent survey indicated that 87.5% of the U.S. population eats fish at least once over the course of a year, 22 older data 23 suggest that in the early 1970s, 40 -50% of the population reported eating fish "seldom or never", which would increase the effective rate of consumption by "users" to ϳ27 g/day at that time. These estimates are also reasonably consistent with those of Stern et al 24 for New Jersey; their data indicate a mean portion size of 168 g and a median consumption rate of ϳ1.3 meals/week, yielding a median per capita consumption rate of ϳ30 g/day.…”

“…The data in Table 2 suggest that a population threshold for Hg effects may exist around the mean level of the Seychelles cohort, i.e., ϳ7 ppm in hair, which is similar to a previous WHO advisory level. 44 According to the analysis of Carrington and Bolger, 22 only ϳ0.2% of U.S. females 16 -49 of age would exceed this threshold. By contrast, ϳ8% of the female population exceeds a hair level of 1.1 ppm, which corresponds to the EPA's reference dose for MeHg.…”