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

MERCURY 434
5. POTENTIAL FOR HUMAN EXPOSURE
The FDA currently has advice for consumers posted on the Internet that recommends that pregnant women
and women of childbearing age, who may become pregnant, limit their consumption of shark and swordfish
to no more that one meal per month (FDA 1998). This advice is given because methylmercury levels are
much higher in these fish species than in the more commonly consumed species. Dietary practices
immediately before pregnancy could also have a direct bearing on fetal exposure, particularly during
pregnancy. The FDA states that nursing mothers who follow this advice, do not expose their infants to
increased health risks from methylmercury (FDA 1998). The FDA further advises that persons other than
pregnant women and women of child-bearing age limit their regular consumption of shark and swordfish
(which typically contain methylmercury at approximately 1 ppm) to about 7 ounces per week (about one
serving) to stay below the recommended maximum daily intake for methylmercury. For fish species with
methylmercury levels averaging 0.5 ppm, regular consumption should be limited to 14 ounces (about
2 servings) per week. A summary of mercury concentrations in the top 10 types of fish consumed by the
general U.S. population is presented in Table 5-13. There is a wide degree of variability in the amount of
fish consumed in the diet by various subpopulations within the United States. Various ethnic groups, as
well as recreational and subsistence fishers often eat larger amounts of fish than the general population and
may routinely fish the same waterbodies (EPA 1995k). If these waterbodies are contaminated, these
populations may consume a larger dose of mercury by virtue of the fact that they consume larger amounts
of fish (from >30 g/day for recreational fishers to >100 g/day for subsistence fishers) with higher
concentrations of mercury in their tissues than individuals in the general population that tend to consume
smaller amounts (6.5 g/day) of supermarket-purchased fish that come from a variety of sources. Table 5-14
provides a summary of the amount of fish consumed daily by the general population, as compared to
recreational and subsistence fishers, including some Native American tribal groups. Those individuals that
consume greater than 100 g of fish per day are considered high-end consumers; they consume more than
10 times the amount of fish estimated to be consumed by members of the general population (6.5 g/day)
(EPA 1995k).
Table 5-15 provides an summary of the estimated total number of persons in the U.S. population (excluding
Alaska and Hawaii), the total female population of reproductive age (ages 15–44 years), and the total
population of children (