Blood mercury levels associated with income, ethnicity and coastal areas

A new study reveals that women living in coastal areas and in the Northeast U.S. were more likely than other women to have blood mercury (BHg) concentrations exceeding levels of concern, as reported in the January 2009 issue of the peer-reviewed journal Environmental Health Perspectives (EHP).

Women living near coastal areas had 3-4 times greater risk of exceeding acceptable levels of mercury than women living in inland regions.

Analysis of data from the National Health and Nutrition Examination Survey (NHANES) collected between 1999 and 2004 showed that women living in the Northeast were the most likely to have BHg concentrations above 3.5 micrograms per liter, with 19% of women (approximately one in five) affected. Proportions of women with BHg above this level were lower among women in the South, West and Midwest census regions, respectively.

Ethnic and economic patterns in the distribution of blood mercury levels were also evident. Mercury levels were higher among women in an ethnic group that included Asian, Native American, Alaskan, Pacific Island and Caribbean Island women. Also women with higher income levels had an increased risk of higher blood mercury levels. Women with a household income of $75,000 per year or more were more likely to have elevated BHg levels compared with women with household incomes of $55,000 or less.

Average blood mercury levels, mercury intake from fish and shellfish, and total fish consumption were strongly associated. During this period (1999 through 2004) there was no clear time-trend in the average BHg levels, mercury intake or the frequency of fish consumption. However, there was a decline in the proportion of women with high BHg levels over this six-year period. Among these women estimated mercury exposure from seafood decreased, however, their total consumption of fish and shellfish did not show a clear trend over the six-year period. These patterns suggest a shift in the type of seafood consumed.

Lead study author Kathryn R. Mahaffey and colleagues wrote, "The change in the estimated intake of Hg in seafood among women of childbearing age over the course of the study suggests a pattern of more discerning series of choices in the type of fish eaten, without an overall reduction of fish consumption."

"Evidence of a switch in the type of fish eaten by women of highest risk for adverse reactions to higher blood mercury concentrations is encouraging," said EHP editor-in-chief Hugh A. Tilson, PhD. "This may suggest that the EPA's advisories and educational initiatives to limit consumption of fish and shellfish with high mercury content are succeeding."

Authors include Kathryn R. Mahaffey, Robert P. Clickner, and Rebecca A. Jeffries.

The article is available free of charge at http://www.ehponline.org/members/2008/11674/11674.html.

EHP is published by the National Institute of Environmental Health Sciences (NIEHS), part of the U.S. Department of Health and Human Services. EHP is an Open Access journal. More information is available online at http://www.ehponline.org/. Brogan & Partners Convergence Marketing handles marketing and public relations for the publication, and is responsible for creation and distribution of this press release.