| Sponsored by: International
Society of Regulatory |
WELCOME TO THE CONFERENCE: HISTORICAL
PERSPECTIVES ON THE DIOXIN ISSUES Terry F. Quill, Esq. On behalf of the International Society of Regulatory Toxicology and Pharmacology, I would like to welcome you. I am Terry Quill. I am a partner in the law firm of Duane, Morris and Heckscher and a member of the ISRTP Council. As an attorney and toxicologist, I have been working on legal, regulatory and technical issues related to dioxin for nearly fifteen years (which, I am sure, is not nearly as long as some of you have been involved with dioxin).
Background EPA conducted its first dioxin risk assessment in 1984. That assessment concerned 2,3,7,8-TCDD. Based on the results of animal studies (the well-known Kociba rat study and a NTP mouse study) EPA calculated an upper-bound one-in-a-million cancer risk dose (RSD) of .006 pg/kg-day. The Agency regulated based on that number. By the late 1980's, many people believed that EPA’s risk-specific dose was too stringent. Many felt that the human evidence did not support the RSD, many thought that the animal studies didn’t support EPA’s RSD, the histology slides from the Kociba study were reanalyzed -- resulting in further support for increasing EPA’s RSD. Indeed, a dioxin working group at EPA proposed raising the RSD. EPA asked its SAB whether new data required EPA to raise its RSD. The SAB concluded that new data were not sufficient to require EPA to raise its RSD (the SAB was not asked what the RSD should be). The SAB also concluded that available data did not necessarily support the current RSD. They recognized that EPA’s dioxin risk estimate was in large part a policy determination. The state was set to reanalyze the risks associated with exposures to TCDD. In 1991, then Administrator Reilly directed the Agency to undertake a dioxin reassessment. In 1994, after extensive consultation with expert panels and opportunities for public comment, the Agency published a reassessment that exceeded 2000 pages. EPA maintained, for the most part, the same RSD. The big difference was that EPA now included within the scope of the reassessment various dioxin and furan congeners and suggested including certain PCBs. This action resulted in a greatly increased exposure estimate and resulted in EPA’s claim that background exposures are at or slightly above a level that would cause adverse effects in humans. Although some supported EPA’s tougher stance, others questioned EPA’s science, use of assumptions and, most significantly, its characterization of dioxin risk. EPA’s SAB also questioned portions of the reassessment and advised the Agency to make some substantial changes. The SAB asked to see EPA’s revised risk characterization, and its revised discussions of toxicity equivalents and dose-response modeling. Perhaps expecting timely revisions and little change to other portions of the reassessment, the SAB did not anticipate the need to re-review the other portions of the reassessment. This past June, five years after the SAB peer review, EPA finally released its revised risk characterization, dose-response and TEF chapters. The Agency also made substantial additions and changes to its other reassessment chapters. This time EPA changed the cancer classification for TCDD from "probable human carcinogen" to "carcinogenic to humans." Based on calculations from a single epidemiological study, EPA also increased its estimated cancer potency for dioxin 100-fold. EPA concluded that the upper-bound cancer risk related to background dioxin exposures was as great as one in one hundred (some have estimated that this comes out to 64,000 annual cancer deaths in the U.S. alone). Finally, EPA concluded that most of our background exposure comes from our food supply. This past July, EPA sought peer review of two of its new chapters -- the risk characterization and TEF chapters. Many of the peer reviewers questioned, among other things, EPA’s cancer classification as well as its potency estimate. Just two days ago, EPA published a notice in the Federal Register (65 Fed Reg 59186) announcing the availability of revised chapters, an upcoming SAB review of the three new chapters (Nov. 1-2), and the close of the comment period (Nov. 17). So, for those of you planning to submit written comments to the SAB, you have a week or two. Unfortunately, EPA did not provide a red-lined version of its revised chapters. One apparent change is EPA’s re-adjustment of its dioxin potency. It appears that the RSD is back up to .001 pg/kg-day, not all that much off of the 1984 value of .006. The big difference is still the estimate for background exposures. Finally, it is important to note that while EPA has been reassessing dioxin, it also has been stringently regulating dioxin releases. For example, due in part to EPA’s regulatory activities, dioxins have been eliminated from pulp mill effluents and emissions from incinerators have improved dramatically. EPA acknowledges this in its draft reassessment. It also acknowledges that environmental and tissue dioxin levels have dramatically decreased. Indeed, we are now looking at things such as back yard burning, residential wood burning and landfill fires as relatively more significant dioxin sources. Well, one might say that we have won the battle -- we’ve controlled major industrial sources of dioxin to the extent that levels in the environmental and human tissues are decreasing. Levels in humans and the environment will continue to decrease. So why does anyone care about the dioxin reassessment? Well, from a legal perspective, I could see it being used to support toxic tort actions and regulatory activities designed to chase that last molecule at contaminated sites. I can only imagine how some might try to use the reassessment for determining residual risks under the Clean Air Act. For these reasons, I think we need a clearer picture of the risk posed by dioxin. Toxic tort actions aside, I believe the significance of the reassessment will depend upon future Agency philosophy and in how that philosophy will influence risk management decisions. For example, will we choose to chase the last molecule of dioxin at any cost or will we make risk management decisions after balancing health risks and benefits with societal costs? Some of these issues may be discussed this afternoon. Purpose A primary purpose of this meeting is to provide a forum for a number of scientists and policy experts who have valuable expertise in dioxin and dioxin-related issues. EPA has provided limited opportunity for open, public scientific debate of its revised chapters -- which stands in stark contrast to the opportunities provided in 1994. In fact, it now seems that this meeting may be the only such forum available before the SAB meeting and before the close of the comment period (by the way, it is my understanding that EPA wants to publish a final document early next year). As you can see by the meeting announcement, we have attempted to be a bit provocative and hope for a lively discussion. In addition to science issues, the revised reassessment also raises important implications for food and public health policy. The risk characterization suggests that current exposures (which come primarily from our food) pose a significant hazard. We hope to address some of these issues in our afternoon sessions. Of course, there are also other important issues that we are likely not to touch upon, such as the potential effect of the reassessment on sectors of the economy and on international trade of food products. It is unclear whether EPA or any government agency has addressed these issues. I do want to acknowledge (and I think it is clear from the agenda) that in this meeting we are not likely to capture all points of view concerning dioxin. Certainly, EPA’s views (particularly concerning the science) are clearly stated in its risk assessment documents and the Agency has been providing numerous informational briefings to a variety of groups. I direct you to EPA’s Web Site (www.epa.gov/ncea/dioxin). As I mentioned, a purpose of this meeting is to provide others an opportunity to discuss the reassessment and its implications. Unfortunately, because of time and funding constraints, we were unable to plan and expand this meeting to debate various views. Finally, as I mentioned, one purpose of this meeting is to help us start thinking about important public health policy issues related to managing dioxin risks. After EPA publishes its final dioxin reassessment, I believe it will be important to continue the policy dialogue with EPA, FDA, USDA, other government and other interested groups. Perhaps this is something ISRTP could consider for a future meeting. |