revised final - Agency for Toxic Substances and Disease Registry ...

MERCURY 469
5. POTENTIAL FOR HUMAN EXPOSURE
protection of high-end fish consumers who routinely and repeatedly consume large quantities of fish from
local bodies of water.
To address this concern, the EPA Office of Water issued guidance to states on sampling and analysis
procedures to use in assessing the health risks from consuming locally caught fish and shellfish. The risk
assessment method proposed by EPA was designed to assist states in developing fish consumption advisories
for recreational and subsistence fishers, including pregnant women, nursing mothers, and children in these
high-end consumption populations (EPA 1995k). Recreational and subsistence fishers consume larger
quantities of fish and shellfish than the general population and frequently fish the same waterbodies
routinely. Because of this, these populations are at greater risk of exposure to mercury and other chemical
contaminants, if the waters they fish are contaminated. The EPA’s Office of Water advises states to use a
screening value of 0.6 ppm mercury (wet weight) in fillets for the general population as a criterion to
evaluate their fishable waters (EPA 1995k). Currently, 1,782 advisories restricting the consumption of
mercury-contaminated fish and shellfish are in effect in 41 states and one U.S. Territory (American Samoa)
(EPA 1998b). The number of mercury advisories currently in effect in each state is shown in Figure 5-7. It
should be noted that mercury is the chemical pollutant responsible in part for over 77% of the fish advisories
issued in the United States (EPA 1998a). It is important to note that 11 states (Connecticut, Indiana, Maine,
Massachusetts, Michigan, Missouri, New Hampshire, New Jersey, North Carolina, Ohio, and Vermont)
currently have state-wide mercury advisories recommending that residents restrict consumption of locally
caught freshwater fish. In addition, 5 states (Alabama, Florida, Louisiana, Massachusetts, and Texas) have
issued statewide coastal mercury advisories for specific marine fish and shellfish species. In two states
(Arizona and Minnesota), wildlife advisories recommending that residents restrict their consumption of
freshwater turtles have been issued.
Subsistence Hunters. Native American populations, such as the Inuit of Alaska and other subsistence
hunters (particularly those living in high latitude areas of the United States), may be exposed to mercury in
wild game (e.g., seals, narwhal, walrus, and other game species or marine mammals). Mercury has been
detected in liver, kidney, and muscle tissues of pilot whales, harp seals, narwhal, and walrus (Meador et al.
1993; Wagemann et al. 1995). Mean total mercury concentrations and methylmercury concentrations were
highest in pilot whale liver tissue: 176 ppm (dry weight) and 8 ppm (dry weight), respectively. In fish,
almost all of the mercury (>95%) body burden is methylmercury (Bloom 1992), but in marine mammals, the
percentage of inorganic mercury is much higher, at least in liver tissue. For example, in Alaskan beluga
whales, mean methylmercury levels were 0.788 ppm (µg/g wet weight), but mean total mercury levels were