Newswise — The peer-reviewed journal Environmental Health Perspectives (EHP) announced today that it has accepted for publication a paper that outlines a new method for calculating a safe level of methylmercury consumption for pregnant women.
Mercury exposure during gestation can increase the risk of adverse neurodevelopmental effects. Accurately determining safe amounts of methylmercury intake for pregnant women could therefore help reduce the number of children who may be exposed to unsafe levels. A study in the April 2004 issue of EHP estimated that number at more than 300,000 newborns per year.
The new model uses a complex probability formula to evaluate various parameters that impact the amount of methylmercury that reaches the fetus, and incorporates new data on the ratio of mercury in cord blood relative to maternal blood. It also uses, for the first time, parameters specific to the third trimester of pregnancy in an effort to reduce the uncertainty in the existing equation.
To calculate safe levels of intake by mothers that would lead to acceptable levels of mercury in cord blood, the study author executed 5,000 iterations of a formula that considered the following: *the ratio of cord blood mercury concentration to maternal blood mercury concentration; *the rate at which methylmercury is eliminated from the body; *maternal blood volume; *maternal body weight; *the amount of mercury that is absorbed relative to how much is ingested; and *the amount of mercury that is present in the blood relative to how much is absorbed.
"In the current analysis, I have made a specific effort to identify distributional data which are specific to pregnancy, and, whenever possible, specific to the third trimester of pregnancy," writes study author Alan H. Stern of the New Jersey Department of Environmental Protection. "Appropriate pregnancy-specific data were identified in four of the six parameters in the model. Third-trimester-specific data sets were identified for three of these four."
In the United States, coal-fired power plants are the biggest source of mercury emissions in the air. The mercury eventually gets into the water supply, where bacteria help it transform into methylmercury. Methylmercury accumulates up the food chain, and humans are exposed to methylmercury when they eat certain types of fish.
"While eating fish can have many health benefits, having an accurate model for determining safe levels of ingestion by pregnant women could help reduce the large numbers of children who currently may be exposed to unsafe levels of methylmercury," said Dr. Jim Burkhart, science editor for EHP.
Now that it's been accepted, the paper will go through the editing process and will appear in print this winter. This article is available online at http://ehp.niehs.nih.gov/docs/2004/7417/abstract.html
EHP is published by the National Institute of Environmental Health Sciences, part of the U.S. Department of Health and Human Services. EHP became an Open Access journal in January 2004. More information is available online at http://www.ehponline.org/.
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