risks vary with dose, said Drinkwater. These new mechanistic criteria could lead to "good science slowing down the regulatory process," said toxicologist William Pease of the University of California at Berkeley School of Public Health. NTP currently funds about 10 rodent bioassays each year; requiring mechanistic studies as well could lead to "more science on fewer compounds," said Pease. Pease said that the same problem could face EPA with its new guidelines, arguing that there was no incentive in most cases for the regulated community to generate mechanistic data. Yet the new guidelines lead the Agency to require an almost complete scientific picture of a substance's carcinogenicity before taking regulatory action, said Pease. "If we begin to limit exposure [based on partial data], there would be incentives to explore the science." "EPA seems to be moving in the right direction," countered Roger McClellan, president of the Chemical Industry Institute of Toxicology. McClellan said that EPAs new guidelines would lead to a more realistic analysis of cancer risks and could begin to address what he sees as overregulation of some substances. McClellan, however, would like to see more changes in the biennial report guidelines. He criticized NTP's decision to continue classifying carcinogens under the labels "known to be a human carcinogen" or "reasonably anticipated to be a human carcinogen." McClellan said the classification system "perpetuates a simplistic system that identifies good versus bad chemicals." McClellan, an NTP science board member, and others had pushed NTP to add categories. Other science board members pointed out that two category labels were written into the cancer report's congressional authorization. —ALAN NEWMAN
EPA particulate matter health effects document criticized
A
n EPA draft assessment of health risks from airborne particulate matter has been strongly criticized by a key Agency advisory committee that claims the document fails to establish a scientific basis for setting new regulations on particulates. The Clean Air Scientific Advisory Committee (CASAC) also asked to review the document a second time after EPA revises it, but a court order may prevent the panel from taking another look. The committee reviewed EPA's draft document on Air Quality Criteria for Particulate Matter in early August. Normally, the panel would have a second or even third opportunity to review any such criteria document, which provides the scientific foundation for a proposed regulation. But a court action by the American Lung Association against EPA has accelerated the rule-making process, so that the agency is required to publish its final particulate matter rule by next year. To meet that schedule, the court limited CASAC to one review each of the document and the staff position paper due in November, which will set the final guidelines for a revised particulate standard. The panel's criticisms echoed those of other skeptics about the reported health effects of particulates (ES&T, August 1995, p. 360A). In an August 31 letter to EPA Administrator Carol Browner summarizing the CASAC review, committee chair George Wolff of General Motors Corp. wrote that the document "has not adequately demonstrated several important linkages that are crucial in relating particulate matter to mortality and/or morbidity." For example, the panel questioned whether exposures estimated from fixed-site monitors,
the kind of data used in the epidemiological studies, truly reflect personal exposure to airborne particles. The EPA document cites 14 examples of the personal exposure data and the fixed-site monitor data showing "no relationship or a poor relationship" and only one example showing "an excellent correlation," but that was the one EPA chose to embrace. "One positive result out of 15 studies is not a strong case for the relationship," wrote Wolff. The panel also found that the document did not establish a convincing link between mortality/ morbidity and any one component of air pollution. Although a reanalysis of particulate health effect data for Philadelphia conducted by the Health Effects Institute and others generally supports a correlation between increased mortality and increased particulates, Wolfe wrote, "the findings do not clearly indicate that the increased mortality associated with increasing indexes of air pollution can be assigned to either [Total Suspended Particulates] or S0 2 alone." These deficiencies raise the committee's concern that EPA is developing its particulate regulations too quickly. "It appears that EPA is leaning toward PM2 5 [particles
