NEWS SCIENCE EPA reassessment finds as much as 20 times less cancer risk from PCBs Polychlorinated biphenyls (PCBs) may pose much less cancer risk than previously thought—in some cases 20 times less—according to an EPA draft reassessment to be released as a final report in September. Although banned from production 20 years ago, PCBs persist in air, water, sediment, soil, and food. The World Health Organization estimates that daily PCB consumption in industrialized countries ranges from 5 to 15 micrograms. PCBs also have been found in at least 271 of some 1200 Superfund sites, according to the Agency for Toxic Substances and Disease Registry (ATSDR). Because PCBs are so prevalent, any change in risks associated with them has widespread repercussions. Once finalized, PCB risk numbers will be placed in EPA and ATSDR databases used by risk assessors nationwide to determine Superfund cleanup standards, fish consumption advisories, and other environmental assessments. PCBs comprise 209 chemicals, but previous cancer studies and risk assessments have focused on only one trademarked PCB-mixture: Aroclor 1260. However, the reassessment considers new data from General Electric Co. (GE) studies of four PCB mixtures: Aroclors 1260, 1254, 1242, and 1016. The four compounds make up most PCBs sold before the ban. The new data uphold the view that PCBs cause cancer in animals, but they downgrade the potency of PCBs. EPA's draft reassessment concludes that PCBs may have from two-thirds to onetwentieth the potency claimed in earlier assessments. The toxicity is based largely on the number and location of chlorine atoms on two connected benzene rings. Cancer potency estimates may vary once the draft is finalized, but EPA's basic conclusion was endorsed by a peer review panel in May. The panel also backed EPA's effort to distinguish the risks
of different PCB mixtures. The delineation will help health officials focus on the worst situations, according to the report's author, James Cogliano, chief of EPA's Quantitative Risk Methods Group. If PCBs are found to be less toxic, industry attorneys believe cleanup standards may drop. However, the report addresses only cancer risk, which may limit its significance, according to Nancy Kim, who directs environmental health assessments for the New York State Department of Health. Her opinion was echoed by others who also noted that cleanup costs, state regulations, and ecological impact are among many issues that factor into cleanup decisions. The report's conclusion might shift attention from cleanup to containment, according to biolo-
gist Peter deFur of Virginia Commonwealth University. Kim and deFur are among scientists who reviewed EPA's draft reassessment. "Once PCBs get out, you may not ever be able to clean them up," deFur said. "But if they are contained, it may be less critical to clean them up immediately." DeFur, a former staff scientist with the Environmental Defense Fund, believes the reassessment's results are protective of public health—if risk assessors follow the report's recommendations. The danger, he said, is that risk managers may use the report's flexibility to develop unjustified lower risk calculations. Given that possibility, deFur urged EPA to oversee the application of the results of the reassessment. For example, if a risk assessor consistently selected options that show that a site poses low risk, EPA should review the data on which the analyst based those assumptions or perhaps visit the site, he said. In some cases the reassessment could increase protection, deFur said, noting that health officials have sometimes
Study questions EPA's claims about MTBE A key oxygenate used to cut wintertime vehicle emissions of carbon monoxide appears not to pose a "substantial human health risk," concludes a National Research Council study. However, the report says the most widely used oxygenate, methyl-ferf-butyl ether (MTBE), may not always reduce CO emissions in cold weather. Examining data used by EPA, the report says oxygenated fuels reduce CO in cold weather by as little as zero to as much as 10%. Noting health effects concerns voiced by residents of Alaska, Wisconsin, New Jersey, and Montana, the report says studies cited by government scientists to support MTBE use suffer from poor design, insufficient numbers of people studied, inadequate assessment of exposure, and the subjective nature of the test results. The NRC report examined federal assessments that concluded that shortterm health effects from MTBE are limited to a sensitive subpopulation. However, the NRC review committee said the government appeared to ignore data that consistently showed an increase in short-term health problems among workers exposed to MTBE on the job. In all, the NRC urged that more definitive studies be conducted on the effectiveness in cold weather of the popular additive and the health effects that may result from its use. Toxicological and Performance Aspects of Oxygenated Motor Vehicle Fuels is available from the National Academy Press; call (800) 624-6242. —JEFF JOHNSON
3 3 2 A • VOL. 30, NO. 8, 1996 / ENVIRONMENTAL SCIENCE & TECHNOLOGY / NEWS
