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Winter 2009 Vol. 8 Number 3

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©Imagemore/Getty Images Phthalates

A Window to Better Risk Assessment at EPA

A group of chemicals known as phthalates has been raising health concerns over the last several years. Found in a variety of consumer products, some phthalates have already been restricted from cosmetics in the European Union, as well as from children's toys in the United States and European Union.

Although few human studies have been conducted to investigate whether phthalates pose a threat to health, animal studies -- particularly with rats -- show that phthalates disrupt male reproductive development, leading to outcomes such as infertility and reproductive tract malformations. The lab research has also shown that the age of the animals at the time of exposure is critical to the severity of the effects; animals exposed in utero suffered the most complications.

Given that humans encounter multiple exposures to phthalates and that exposure to different phthalates leads to similar outcomes in lab animals, the U.S. Environmental Protection Agency should pursue a cumulative risk assessment, says a new report from the National Research Council. Furthermore, the assessment should not only include phthalates but also other chemicals that could produce similar effects on male reproductive development.

"If a cumulative risk assessment focuses solely on phthalates and excludes other chemicals, it would be artificial and could seriously underestimate risk," said Deborah Cory-Slechta, chair of the committee that wrote the report. "We need to examine how all these chemicals work together collectively and not individually."

Currently when conducting cumulative risk assessments, EPA often considers only chemicals that are similar in makeup, on the assumption that they have the same chain of reactions that lead to a final health outcome. However, that practice ignores how exposures to different chemicals may result in the same health effect. The committee called on EPA to change its strategy and apply the recommended approach for phthalates to any cumulative risk assessment. For instance, when looking at what could lead to cognitive deficits consistent with IQ reduction in children, EPA could evaluate the risk of combined exposures to lead, methylmercury, and polychlorinated biphenyls and not just examine each chemical individually.

The committee emphasized that it may be challenging for EPA to evaluate the multiplicity of human exposures resulting in common health outcomes, but it is feasible. Such a shift in approach would entail substantial efforts by EPA to define and set priorities among the most prominent adverse health effects of toxins, but it directly reflects EPA's mission to protect human health.   -- Jennifer Walsh

Phthalates and Cumulative Risk Assessment: The Tasks Ahead. Committee on the Health Risks of Phthalates, Board on Environmental Studies and Toxicology, Division on Earth and Life Studies (2008, 208 pp.; ISBN 0-309-12841-2; available from the National Academies Press, tel. 1-800-624-6242; $46.00 plus $4.50 shipping for single copies).

The committee was chaired by Deborah Cory-Slechta, professor, department of environmental medicine, University of Rochester School of Medicine and Dentistry, Rochester, N.Y. The study was funded by the U.S. Environmental Protection Agency.

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Copyright 2009 by the National Academy of Sciences