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December 11, 2013
Women avoiding mercury-laden fish

The blood-mercury levels in women of child-bearing age have decreased substantially since 1999 to 2000, said the EPA in a new report. 

Based on survey data developed by the Centers for Disease Control (CDC), the Agency states that the geometric mean blood total mercury (THg) in 1999 to 2000 was 1.21 times higher than the geometric mean across the subsequent 10 years (2001 to 2010) for women 16 to 49 years of age.  For blood methyl mercury (MeHg), the CDC’s data indicate the geometric mean for the group in 1999 to 2000 was 1.51 times higher than the geometric mean across the subsequent 10 years. 

MeHg, a combination of elemental mercury and organic material, bioaccumulates in aquatic species and presents the highest mercury health risks to people.

NHANES program

EPA’s report is based on information collected by CDC’s National Health and Nutrition Examination Survey (NHANES) program.  The program began in the early 1960s and has been conducted as a series of surveys focusing on different population groups or health topics.  In 1999, the survey became a continuous program that has a changing focus on a variety of health and nutrition measurements to meet emerging needs.  The survey examines a nationally representative sample of about 5,000 persons each year.  These persons are located in counties across the country, 15 of which are visited each year.

Consumed amount unchanged

Exposure to MeHg in people in the United States is almost exclusively through the consumption of fish and shellfish, almost all of which contain traces of mercury.  For most people, the risk from mercury by eating fish and shellfish is not a health concern.  Yet some fish and shellfish contain higher levels of mercury that may harm an unborn baby or young child’s developing nervous system. 
The EPA reports that during the survey period there was very little change in the amount of fish consumed.  The decrease in the ratio of mercury intake to fish consumed suggests that women may have shifted to eating types of fish with lower mercury concentrations.  The report focuses on trends in mercury levels based mostly on consumption of ocean fish, says the EPA.  It does not reflect trends in levels in communities that depend on locally caught fish for subsistence.        

Fish to avoid

Both the EPA and the U.S. Food and Drug Administration have developed public outreach and education regarding mercury in fish, including issuance of advisories on fish consumption in 2001 and 2004.  The agencies note that shark, swordfish, king mackerel, and tilefish have high levels of mercury and should not be consumed by women who may become pregnant, pregnant women, nursing mothers, and young children.  Five of the most commonly eaten fish that are low in mercury are shrimp, canned light tuna, salmon, pollock, and catfish. 

Global air pollutant

Coal-burning power plants are the largest human-caused source of mercury emissions in the United States, accounting for over 50 percent of all domestic human-caused mercury emissions.  However, airborne mercury is also a global pollutant, crossing national boundaries.  The EPA has estimated that about one-quarter of U.S. emissions from coal-burning power plants is deposited within the contiguous United States and the remainder enters the global cycle.

The EPA has undertaken major regulatory actions in an attempt to control mercury releases from power plants.  In June 2013, the Agency proposed new effluent guidelines for steam electric power plants, which currently account for more than half of all toxic pollutants discharged into streams, rivers, and lakes from industrial facilities in the United States.  In February 2012, the EPA issued the mercury air toxics standards for fossil-fuel fired power plants. Compliance with the standards may take up to 4 years.

Trends in Blood Mercury Concentrations and Fish Consumption Among U.S. Women of Childbearing Age, NHANES, 1999-2010

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