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

MERCURY 224
2. HEALTH EFFECTS
mercury is 0.49 µg/day for infants (aged 6–11 months), 1.3 µg/d for 2-year-old children, 2.9 µg/day for
females aged 25–30 years, and 3.9 µg/day for males 25–30 years of age. Expressed on a per body weight
basis, the intake for all age groups, except for 2-year-old children, was approximately 0.05 µg/kg/day
(Clarkson 1990; Gunderson 1988). More recently, MacIntosh et al. (1996) estimated mean dietary
exposure of 8.2 µg/d (range, 0.37–203.5 µg/day) for females and 8.6 µg/day (range, 0.22–165.7 µg/day)
for males. For an average body weight of 65 kg for women and 70 kg for men, the daily intakes of
mercury would be 0.126 µg/kg/day (range, 5.7–3,131 ng/kg/day) for women and 0.123 µg/kg/day (range,
3.1–2,367 ng/kg/day) for men, respectively. Lack of data about the actual amount of food consumed
accounted for 95% of the total uncertainty for mercury. This was especially true for consumption levels of
canned tuna and other fish (MacIntosh et al. 1996)
The Food and Drug Administration (FDA, 1996) has posted on the Internet advice for consumers
recommending 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. This advice is given
because methylmercury levels are relatively high in these fish species. The FDA’s advice covers both
pregnant women and women of child-bearing age who might become pregnant, since dietary practices
immediately before the pregnancy could have a direct bearing on fetal exposure, particularly during the
first trimester of pregnancy. The FDA also states that nursing women who follow this advice will not
expose their infants to increased health risks from methylmercury (FDA 1996). For the general population
(other than pregnant women and women of child-bearing age), the FDA advises limiting the regular
consumption of shark and swordfish (which typically contain methylmercury at 1 ppm) to about 7 ounces
per week (about one serving). This level of consumption results in methylmercury exposures below the
U.S. FDA acceptable daily intake level for mercury. For fish species with methylmercury levels averaging
0.5 ppm, regular consumption should be limited to 14 ounces per week. Recreational and subsistence
fishers who eat larger amounts of fish than the general population and routinely fish the same waters may
have a higher exposure to methylmercury if these waters are contaminated (EPA 1995). People who
consume greater than 100 grams of fish per day are considered high-end consumers. This is over 10 times
the amount of fish consumed by members of the general population (6.5 g/day) (EPA 1995). No
consumption advice is necessary for the top 10 seafood species, which make up about 80% of the seafood
market: canned tuna, shrimp, pollock, salmon, cod, catfish, clams, flatfish, crabs, and scallops. The
methylmercury in these species are generally less than 0.2 ppm, and few people eat more than the
suggested weekly limit of fish (i.e., 2.2 pounds). More information on exposure to methylmercury and the
levels in fish can be found in Section 5.5, General Population and Occupational Exposures.