Methylmercury exposure in Wisconsin: A case study series

Many popular varieties of commercially sold fish, including tilefish, seabass, shark, and swordfish, contain enough mercury so that eating them once or twice a month can lead to high mercury body burdens. Wisconsin has issued mercury-based sport-fish consumption advice to people of all ages since 1985. Wisconsin's advisory was revised in 2000 to address all inland waters and again in 2004 to integrate information about sport-caught fish with advice for commercially sold fish. Because of the increased popularity of fish as a source of dietary protein, a significant percentage of the US population may be at risk of methylmercury-induced health problems. Although several studies have assessed mercury exposure among children and women of child-bearing age, very little is known about mercury body burdens among men or postmenopausal women. This article describes fish consumption and mercury exposure among 14 people who consumed fish twice a week or more and 1 person who ate no fish. Steady-state blood mercury levels available for 10 adults and 1 child ranged from <5 to 58 microg/L and correlated well with dietary mercury intake estimates. Three of these individuals reported vague, subclinical symptoms such as mental confusion, sleep difficulty, balance problems, or visual disturbances, which improved after their mercury levels returned to normal.