Blood mercury levels in young children and childbearing-aged women--United States, 1999-2002.

Exposure to high levels of mercury (Hg) can cause neurologic and kidney disorders. Because methylated Hg (methyl-Hg) in the aquatic environment accumulates in animal tissues up the food chain, persons in the United States can be exposed by eating freshwater fish, seafood, and shellfish. Exposure of childbearing-aged women is of particular concern because of the potential adverse neurologic effects of Hg in fetuses. To determine levels of total blood Hg in childbearing-aged women and in children aged 1-5 years in the United States, CDC's National Health and Nutrition Examination Survey (NHANES) began measuring blood Hg levels in these populations in 1999. This report summarizes NHANES results for 1999-2002 and updates previously published information. The findings confirmed that blood Hg levels in young children and women of childbearing age usually are below levels of concern. However, approximately 6% of childbearing-aged women had levels at or above a reference dose, an estimated level assumed to be without appreciable harm (> or =5.8 microg/L). Women who are pregnant or who intend to become pregnant should follow federal and state advisories on consumption of fish.