EPA tries new tests for toxicity

RESEARCH TRIANGLE PARK -- The health risks of pesticides are fairly well known.

But what about chemicals such as the plastic additives bisphenol A and phthalates that were not designed to be toxic?

For more than 70 percent of compounds on the market, little or no data exist on whether they cause cancer, disrupt reproduction or damage unborn life.

About 40 scientists at the Environmental Protection Agency in Research Triangle Park are working on filling that data gap. Led by Robert Kavlock, director of the EPA's National Center for Computational Toxicology, the group is working on ToxCast, a program to screen chemicals for their potential to harm people and the environment.

Instead of live-animal tests developed more than 40 years ago, ToxCast uses screening technology gleaned from drug research. Computers then turn the results of about 600 ToxCast tests per chemical into quick-to-grasp, three-dimensional maps.

"We look for a fingerprint of the biological activity of the chemical," Kavlock said.

A ToxCast fingerprint can be ready in a few weeks and costs about $25,000, where live-animal testing takes months and can cost $10 million to $12 million per chemical.

"They're spearheading a paradigm shift in toxicology testing," said Dr. Thomas Hartung, professor of evidence-based toxicology and director of the Center for Alternatives to Animal Testing at Johns Hopkins Bloomberg School of Public Health.

Since the EPA formed the National Center for Computational Toxicology five years ago, screening of about 1,000 chemicals has been under way, representing about 10percent of all compounds on the ToxCast list.

But so far, ToxCast fingerprinting has only been used to assess a real-life risk in one instance: the eight dispersants the EPA allowed BP to use on the Gulf of Mexico oil spill last summer. One dispersant, Corexit 9500, had raised particular concerns.

Within four weeks, EPA scientists in RTP, their collaborators at the National Institutes of Health and at contract labs in Durham and Baltimore completed the fingerprinting, said David Dix, a research biologist at the National Center for Computational Toxicology. BP was allowed to continue to use the detergent.

Since then, the Food and Drug Administration also joined the ToxCast effort. Still, it will probably take another five to 10 years before ToxCast fingerprints can be used regularly to predict a chemical's potential harm.

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