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22 October 2002

New Study Finds Upper-Income Fish Eaters Exposed to Dangerous Levels of Mercury

Study Released Today in Environmental Health Perspectives Finds Levels in Women 10x Suggested, Children 40x

[RESEARCH TRIANGLE PARK, NC] A new study published today in the science journal Environmental Health Perspectives found that individuals whose diet included large amounts of fish had dangerously high levels of mercury in their blood. Fish accumulate methylmercury in their blood, and it cannot be cooked out. Even modestly excessive exposure to mercury has been shown to impair human immune, reproductive, and cardiovascular systems.
In the study, all the patients of a San Francisco Internal Medicine practice who came in for an office visit during a one-year period were evaluated. Of these 720 patients, 123 received further testing based on either their symptoms or their diet. Study participants were mostly middle- to higher-income patients.
Mercury levels in tested blood and hair correlated with fish consumption, particularly swordfish, the study authors concluded. “By abstaining from fish, these high levels of mercury were easily reduced, but it took greater than 21 weeks [to do so] in many individuals.” they write.
Mercury levels in tested women averaged 10 times the levels recommended by the U.S. Environmental Protection Agency and the National Academy of Sciences. Levels in men were close behind, while some of the children tested were found to have levels 40 times those recommended. Nearly 90% of those tested were above the recommended levels.
The study participants were largely professionals, including physicians, scientists, banking professionals, business owners, Internet executives, lawyers, investment brokers, and corporate executives. The group also included retirees and homemakers. Seven children were tested.
The patients studied ate 30 types of fish, all from commercial sources. The highest correlation between diet and mercury levels occurred with swordfish.
The relatively high incomes of the study participants may have related to their dietary choices. Patients regularly indicated eating sushi (ahi, yellowtail, mackerel, salmon, etc.), sashimi, shrimp, prawns, crab, oysters, and scallops, among other seafood.
“One child, a 50-pound, seven-year-old boy, had an initial hair level [14 times recommended levels]. He ate fish most of his life. His current regimen of albacore steaks, Ahi [CAPPED IN ARTICLE?]steaks, canned tuna, and salmon has been consistent for the last four years. In 1999, he ate king mackerel twice a week for 6 months,” the authors noted. “After stopping fish, hair and blood levels began to decline.” After nearly 32 weeks without fish, his blood mercury had returned to acceptable levels.
All study patients with unexplained symptoms or high mercury levels were instructed to either stop all fish for six months or to eat only fish that are known to be low in mercury, such as salmon, tilapia, sole, sardines, and small shellfish.
The study was authored by Jane M. Hightower, M.D., of the California Pacific Medical Center, and Dan Moore, Ph.D., of the Geraldine Brush Cancer Research Institute, both of San Francisco.
EHP is the journal of the National Institute of Environmental Health Sciences, part of the U.S. Department of Health and Human Services. More information is available online at http://www.ehponline.org.

Editor’s note: A full copy of the report is available online here http://ehpnet1.niehs.nih.gov/docs/2003/5837/abstract.html, or by fax or e-mail (PDF format) to working media at no charge. Go to www.ehponline.org/press, contact using phone number listed, or e-mail adams6@niehs.nih.gov.