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

MERCURY 468
5. POTENTIAL FOR HUMAN EXPOSURE
methylmercury body burden. Because mercury is associated primarily with muscle tissue in the body of a
fish, rather than with fatty deposits, trimming and skinning of mercury-contaminated fish does not reduce the
mercury content of the fillet portion, as is the case for PCBs, dioxins, and other organochlorine pesticides
(Armbuster et al. 1988; Gutenmann and Lisk 1991).
Several recent studies have documented higher fish consumption rates among subsistence fishers, some of
which are Native American populations. In 1990, there were an estimated 1,959,234 Native Americans in
the United States, including 1,878,285 American Indians, 57,152 Eskimos, and 23,797 Aleuts (Paisano
1998). Approximately 218,320 Native Americans were living on ten reservations and tribal lands, and these
people accounted for half of all Native Americans living on reservations. Therefore, approximately 440,000
Native Americans live on reservations. The median family income in 1990 for Native Americans was
$21,750, about 65% of the $35,225 median income of all U.S. families. In addition 27% of all Native
Americans are living in poverty, compared with 10% of the general population. In a study of 11 Alaskan
communities, Nobmann et al. (1992) reported an average daily fish consumption rate of 109 g/day. This
average consumption rate for subsistence fishers is more than 16.8 times the mean fish consumption rate of
6.5 g/day estimated for the general population (EPA 1995k). A recent study of fish consumption patterns
among the Umatilla, Nez Perce, Yakama, and Warm Springs tribes of the Columbia River Basin in
Washington and Oregon (CRITFC 1994) found that adults in these tribes consume an average of 59 g/day
and that the 95th percentile of fishers consume 170 g/day of fish. The mean consumption rate for the four
tribes is more than nine times the mean fish consumption rate estimated for the general population (EPA
1995k). Furthermore, the consumption rate for Native American children (5 years and younger) from these
four tribes was 20 g/day (a rate over 3 times that for adults in the general population) (see Section 5.6).
In order to reduce methylmercury exposure from consumption of mercury-contaminated fish and shellfish,
consumption advisories are issued by states recommending that individuals restrict their consumption of
specific fish and shellfish species from certain waterbodies where mercury concentrations in fish and
shellfish tissues exceed the human health level of concern. This level of concern is set by individual state
agencies, but several states use the FDA action level of 1 ppm to issue advisories recommending no
consumption or restricting consumption of contaminated fish and shellfish from certain waterbody types
(e.g., lakes and/or rivers). The FDA value was designed to protect consumers from the health risks
associated with consumption of fish and shellfish that are shipped in interstate commerce and that are
purchased in commercial markets. The FDA action level was not intended to be used as a criterion for the