| Sponsored by: International
Society of Regulatory |
FOCUS OF THE CONFERENCE
For the past decade, EPA has been attempting to reassess the hazards posed by 2,3,7,8-etrachlorodibenzo-p-dioxin and related compounds (generally, "dioxins"). EPA published a draft dioxin reassessment in 1994. In response to recommendations and concerns expressed by its Science Advisory Board and other commenters, EPA agreed to redraft significant portions of its dioxin reassessment. Recently, EPA released entirely new reassessment chapters concerning dose-response modeling and toxicity equivalence factors (TEFs), and significantly revised health and exposure chapters. EPA also released a new Integrated Summary and Risk Characterization chapter. Despite EPA’s findings that dioxin exposures have decreased precipitously over the last ten years and evidence that exposures will continue to decrease -- all due primarily to effective regulatory programs -- the Agency paints a dire picture concerning the threat "background" dioxin exposures pose to human health. For example, since its 1994 draft of the reassessment, EPA has determined that dioxin is a "known-human carcinogen," that it is a more potent carcinogen and that it may cause significant cancer and non-cancer effects in humans at background levels of exposure. EPA concludes that current background exposures (much of it from food) to dioxin and related compounds pose an upper-bound human cancer risk as high as one in a hundred. If EPA is correct, as many as 64,000 annual cancer deaths in the U.S. and 1,280,000 annual cancer deaths worldwide could be attributed to background dioxin exposures. Many in the scientific community, however, challenge EPA’s conclusions asserting that the Agency failed to fully weigh the science, ignored portions of the scientific evidence and relied upon overly conservative assumptions to draw its conclusions. For example, it has been pointed out that more than 90 percent of EPA’s estimated human background exposures to "dioxins" are exposures to non-TCDD compounds, many of which have not been shown to cause cancer in animals or humans. Further, it has been asserted that human epidemiologic studies fail to demonstrate a cancer or non-cancer hazard to humans at background levels of exposure. Indeed, many higher human exposures (such as some occupational and accidental exposures) have not been clearly shown to cause adverse human effects. |