US EPA - Mercury Study Report to Congress - Vol. IV - An Assessment of Exposure to Mercury in the United States
Section 112(n)(1)(B) of the Clean Air Act (CAA), as amended in 1990, requires the U.S. Environmental Protection Agency (U.S. EPA) to submit a study on atmospheric mercury emissions to Congress. The sources of emissions that must be studied include electric utility steam generating units, municipal waste combustion units and other sources, including area sources. Congress directed that the Mercury Study evaluate many aspects of mercury emissions, including the rate and mass of emissions, health and environmental effects, technologies to control such emissions, and the costs of such controls.
In response to this mandate, U.S. EPA has prepared an eight-volume Mercury Study Report to Congress. This document is the exposure assessment (Volume IV) of the Mercury Study Report to Congress. The exposure assessment is one component of the risk assessment of U.S. anthropogenic mercury emissions. The analysis in this volume builds on the fate and transport data compiled in Volume III of the study. This exposure assessment considers both inhalation and ingestion exposure routes. For mercury emitted to the atmosphere, ingestion is an indirect route of exposure that results from mercury deposition onto soil, water bodies and plants and uptake through the food chain. The analyses in this volume are integrated with information relating to human and wildlife health impacts of mercury in the Risk Characterization Volume (Volume VII) of the Report.
National Assessment of Mercury Exposure from Fish Consumption
A current assessment of U.S. general population methylmercury exposure through the consumption of fish is provided in this volume. This assessment was conducted to provide an estimate of mercury exposure through the consumption of fish to the general U.S. population. It is not a sitespecific assessment but rather a national assessment. This assessment utilizes data from the Continuing Surveys of Food Intake by Individuals (CSFII 89-91, CSFII 1994, CSFII 1995) and the third National Heath and Nutrition Examination Survey (NHANES III) to estimate a range of fish consumption rates among U.S. fish eaters. Both per capita and per user (only individuals who reported fish consumption) were considered. For each fish-eater, the number of fish meals, the quantities and species of fish consumed and the self-reported body weights were used to estimate mercury exposure on a body weight basis. The constitution of the survey population was weighted to reflect the actual U.S. population. Results of smaller surveys on "high-end" fish consumers are also included.
These estimates of fish consumption rates were combined with fish species-specific mean values for measured mercury concentrations. The fish mercury concentration data were obtained from the National Marine Fisheries Service, Bahnick et al., (1994), and Lowe et al., (1985). Through the application of specific fish preparation factors (USDA, 1995), estimates of the range of methylmercury exposure from the consumption of fish were prepared for the fish-consuming segment of the U.S. population. Per kilogram body weight estimates of methylmercury exposure were determined by dividing the total daily methylmercury exposure from this pathway by the self-reported body weights.
Estimates of month-long patterns of fish and shellfish consumption were based on the data reporting frequency of fish/shellfish consumption obtained in the third National Health and Nutrition Examination Survey (NHANES III) conducted between 1988 and 1994. Combining these frequency data with other information on respondents in NHANES III (i.e., 24-hour recall data and self-reported body weight of subjects), and mean mercury concentrations in fish/shellfish, these projected month-long estimates of fish/shellfish consumption describe moderate-term mercury exposures for the general United States population.