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PBDEs in breast milk: levels higher in United States than in Europe.

The commercial flame retardants that manufacturers add to electrical appliances and building materials undoubtedly save lives. However, mounting evidence shows that these chemicals--which bioaccumulate in the tissues of fish, animals, and humans--can be toxic and potentially carcinogenic. Of particular concern are poly-brominated diphenyl ethers (PBDEs), a class of chemicals that make up roughly 37% of the worldwide market for flame retardants. In the current issue, researchers led by Arnold Schecter of the University of Texas Health Sciences Center in Dallas provide the first published data set of PBDEs in breast milk samples obtained from women in the United States, revealing that U.S. women have the highest PBDE concentrations detected in the world to date [EHP 111:1723-1729].

Schechter and colleagues analyzed a total of 47 samples from white, black, and Hispanic nursing mothers aged 20-41. Of these, 24 were obtained from the Austin Mother's Milk Bank, a Texas-based nonprofit organization, and 23 were obtained from the University of Texas Southwestern Medical Center in Dallas. The researchers confined their analyses to 13 PBDE chemical structures known as congeners.

The researchers found every sample to be contaminated with PBDEs to some extent. Further, their results indicate that PBDE concentrations in these breast milk samples were 10-100 times higher than those detected in breast milk from women who lived in Europe, and in fact were the highest detected in the world. The lowest concentration in an individual U.S. sample, expressed as the sum of all detected congeners in breast milk lipids, was 6.2 parts per billion (ppb), and the highest was 419.0 ppb. The median was 34.0 ppb, and the mean was 73.9 ppb. Neither the duration of lactation nor the number of children each mother had ever nursed was associated with PBDE levels in breast milk.

Schecter and colleagues do not recommend that mothers not nurse, but do suggest that the detection of these compounds in breast milk raises concerns for nursing infants, who are more susceptible than adults to the effects of exogenous chemicals. Toxicity data for PBDEs are rare, but limited studies in animals have linked the chemicals to possible endocrine, hepatic, reproductive, and neurodevelopmental effects, in addition to cancer.

It is unclear how humans are exposed to these compounds. Possible sources include ingestion of contaminated food and inhalation of airborne PBDEs at home or in occupational settings within the electronics and computer industries, the authors say. However, Schecter and colleagues also found high levels in women with no known occupational exposure. These findings suggest the need for studies that investigate animal fat as a primary source of exposure within the U.S. population, the authors write.

Based on their established toxicity, two classes of PBDEs--penta-BDEs and octa-BDEs--will be officially banned by the European Union in 2004, although most European manufacturers have already voluntarily ceased production of these chemicals. Large quantities of deca-BDEs are still produced in both the United States and Europe. These compounds, being large and bulky, cross the cell membrane with difficulty, rendering them less toxic than their penta- and octa-brominated counterparts. However, deca-BDEs may degrade in the environment to lesser-brominated forms, thus creating another potential source of human exposure. Schecter and colleagues suggest that more data are needed to determine the levels and distribution of PBDEs in the environment, routes of intake, and health effects.
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Title Annotation:Science Selections
Author:Schmidt, Charles W.
Publication:Environmental Health Perspectives
Date:Nov 1, 2003
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