SAB review of dioxin risk reassessment delayed until at least end of year The long-running EPA dioxin reassessment has been delayed again, and a second review by the EPA Science Advisory Board (SAB) will be put off until the end of the year. The six-month delay, EPA officials say, is the result of the turmoil of the federal shutdowns, coupled with a lengthy peer review process. More than a dozen university, private, and state risk experts are helping EPA rewrite parts of the dose-response chapter and all of the risk characterization chapter, which summarizes the reassessment's data and discusses the options to control the risks posed by exposures to dioxin and related compounds. Last September, the SAB Executive Committee specifically criticized these sections and urged EPA to modify these two chapters of the nine-chapter document. They also called on EPA to rely more strongly on outside peer reviews {ES&T, November 1995, 492A). Consequently, throughout this latest review, EPA has involved non-EPA scientists. In September, some 30 scientists representing industry, civic, environmental, and other perspectives are scheduled to review the final modified sections, according to William Farland, director of EPA's National Center for Environmental Assessment. The latest version will include much more tissue-burden data linking the amount of dioxin in cells with adverse effects, said George Lucier, director of the National Institute of Environmental Health Sciences Environmental Toxicological Program. In a review last year, some SAB members and members of a panel SAB created to review the draft criticized EPA for failing to prove its conclusion that adverse health effects, especially noncancer effects, may be occurring at or near current dioxin exposure levels. The revised reassessment, Lucier said, will include more specific information on noncancer health risks. The data continue to show that current dioxin body-burdens are close to exposures associated with adverse health effects, said Lucier. And these findings, he
Beef consumption as a source of dioxin exposure will be addressed in the EPA reassessment with the addition of new analyses of beef samples.
predicted, may lead to increased pressure on EPA to set a national strategy to reduce dioxin levels. The revised reassessment will also present options risk assessors can use to determine risks, including a "margin of exposure" approach similar to that used by the World Health Organization. The option comes in response to industry criticisms that EPA's approach to estimating dioxin's risks, particularly carcinogenic risks, was too conservative. In several other areas, EPA is less clear on how it will incorporate new health and exposure data into the reassessment. For example, the agency is wrestling with how it should address new research findings that show adverse behavioral, immune system, and thyroid effects in children exposed to dioxin in breast milk, Farland said. Such effects appeared at dioxin levels typical of urban environments, but the biological changes may be observable but not adverse. "We don't want to overinterpret what these indicators may mean," Farland said. "Their significance is uncertain. We will do our best job to lay out perspectives." Additional dietary information also will be included in the reassessment. For example, analyses of 63 beef samples show a threefold decrease in the level of dioxin originally thought present,
3 3 8 A • VOL. 30, NO. 8, 1996 / ENVIRONMENTAL SCIENCE & TECHNOLOGY / NEWS
Farland said. Although the decrease may appear significant, Farland described it as "slight" and "not unexpected given the kinds of controls that have been put on dioxin." The new beef estimate, however, continues to have the uncertainties associated with small sample size, Farland noted. Testing costs prevented the agency from analyzing more food or blood serum samples, he said, noting that dioxin tests cost from $1200 to $2000 each. EPA plans to analyze pork, poultry, and milk samples, but much of this data will not be available until after SAB's review. The agency does, however, have new fish consumption data that could help risk assessors better calculate exposure levels for populations whose diet is rich in fish. "This becomes particularly important for community-based assessments where you want to make sure you are not dealing with a group at special risk," Farland explained.
The latest version will include more tissueburden data, linking the amount of dioxin with adverse effects. The reassessment's exposure chapters will also include new emissions and effluent data from 180 facilities including pulp and paper mills, cement kilns, and solid waste incinerators, said David Cleverly, co-author of the reassessment's exposure sections. In response to criticisms that EPA data failed to credit improved control technologies that have reduced dioxin emissions, the agency will partition emissions and effluent figures by time—pre- and post-1990—and by industry, type of facility, and pollution control technology. Several scientists involved in the five-year-long reassessment stressed that, overall, the revisions should present clearer information for risk managers and public officials to use in weighing regulatory options to protect the public. —PAT PHIBBS
