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Scientific Experts' Recommendations on Dioxin Given Uneven Consideration by EPA

Scott Jensen (703) 741-5834
May 21, 2010

EPA requests input from National Academy of Science, ignores some major recommendations

ARLINGTON, VA (May 21, 2010) – The U.S. Environmental Protection Agency (EPA) today issued its response to a 2006 report by the National Academy of Sciences (NAS) — “Health Risks from Dioxin and Related Compounds: Evaluation of the EPA Reassessment,” which was, in many ways critical of the agency’s draft reassessment. The following statement may be attributed to ACC Assistant General Counsel David Fischer:

“While it’s taken over 3 years, EPA has responded to important recommendations made in 2006 by the NAS expert scientific panel, whose independent guidance EPA had specifically requested. We believe that EPA’s response is a ‘mixed bag.’ While EPA’s review of the expert panel’s recommendations is a step in the right direction, it’s unclear why EPA would ultimately reject critical parts of the review it sought from the NAS.”

 “We’re very troubled that EPA disregarded the NAS’ recommendation by opting for a “linear” dose-response model for cancer. The linear model overestimates cancer risk by assuming that exposure to dioxin at any level presents a health risk. This approach is not supported by what scientists now know about dioxin. In fact, it runs counter to other respected health and environment authorities, as well as to the specific guidance of the NAS, which recommended that EPA use the scientifically justified ‘threshold’ model of risk assessment. A threshold model incorporates the most current science, which has found that exposures below certain thresholds pose no human health risk.

 “On the positive side, EPA deserves credit for following the academy’s recommendation to utilize physiologically-based pharmacokinetic (PBPK) modeling. This biological model is important, because it takes into account real-world factors, such as metabolism and absorption. Utilizing a PBPK model is a significant factor in determining dioxin’s potential effects on the human body and conducting a dose-response assessment.

“Unfortunately, however, while EPA appeared to heed NAS’ recommendation to develop a dioxin reference dose (RfD) using human data, the agency did not use the best available science, and based the RfD on questionable research. As a result, the agency exaggerates health effects expected from normal dietary exposure.

“While we are glad EPA took the time to review the NAS evaluation, we are disappointed the agency will not be giving others a fair opportunity to do the same due to an unreasonably brief public comment period before the Science Advisory Board convenes to review EPA’s response.

Going forward, we hope EPA will reconsider this truncated comment period, so as to provide sufficient time for input from the scientific community.  We also hope the agency will reconsider some of its conclusions, which we believe are unsubstantiated by the weight of scientific evidence.”

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