Objectives: We evaluated the effectiveness of biomonitoring as an intervention against methylmercury exposure.
Methods: During 2004, the Wisconsin Department of Health Services assessed fish consumption and methylmercury exposure among 2,031 men and women who responded to a statewide press release. People whose hair mercury levels exceeded 1 microgram per gram (microg/g) were advised to reduce their intake of large, predatory fish. Others were informed that mercury exposure was not an issue for them and were encouraged to continue to eat fish as part of a healthy diet. In 2008, follow-up questionnaires and hair sampling kits were mailed to all 2004 study participants.
Results: Completed surveys and hair samples were received from 1,139 individuals. While overall fish intake for this group increased slightly, from 8,561 to 8,785 servings per month between 2004 and 2008, the intake rate was significantly reduced among people whose 2004 hair mercury levels were >1 microg/g, and 30% of the cohort reported eating different types of fish or smaller fish in 2008. The number of people who had a hair mercury level >1 microg/g fell from 300 in 2004 to 206 in 2008.
Conclusions: Hair mercury analysis and explanatory result letters appear to have had a long-term effect on methylmercury exposure and the selection of fish. These findings support the public health benefit of methylmercury screening in conjunction with results-based education among frequent consumers of commercial and sport-caught fish.