After much delay, the Environmental Protection Agency (“EPA”) has released its findings regarding the non-cancer risks associated with dioxin.1 The findings have been included in the Integrated Risk Information System (“IRIS”), a comprehensive database maintained by EPA. In releasing separately its assessment of the non-cancer portion, EPA disregarded widespread concerns of commenters that releasing the non-cancer portion in advance of completing the cancer reassessment would confuse both the general public and environmental risk managers.
The non-cancer portion of EPA’s dioxin reassessment, Reanalysis of Key Issues Related to Dioxin Toxicity and Response to NAS Comments, Volume 1 (“Reanalysis Volume 1”), is now posted on EPA’s web site with a link to the IRIS site. No time table has been set for release of Volume 2, containing the full dioxin cancer reassessment, but EPA reports that it will be released “as expeditiously as possible.”
MORE STRINGENT EXPOSURE STANDARDS MAY RESULT
This is the first-ever non-cancer toxicity value established by EPA for dioxin, and the most stringent non-cancer intake value ever published by either a United States or international agency. EPA established a Reference Dose (“RfD”) of 0.7 picograms per kilogram bodyweight per day (pg/kg-day) for 2,3,7,8-tetrachlorodibenzo-p-dioxin (“TCDD”), which EPA believes to be the most toxic compound among the polychlorinated dibenzo-p-dioxins (“PCDDs”), polychlorinated dibenzofurans (“PCDFs”), and certain coplanar polychlorinated biphenyls (“cPCBs”). According to EPA’s assessment, the RfD is the amount below which daily exposure to dioxin over the course of a lifetime is not expected to result in non-cancer health effects.
It is expected that the dioxin RfD will serve as the basis for significantly more stringent environmental remediation standards, as well as air and water quality regulations. In fact, the EPA press release for finalization of the assessment stated that the RfD “could be considered” in establishing cleanup standards at dioxin-contaminated Superfund sites, in reviewing the dioxin drinking water standard as part of the EPA’s next five-year review, and in determining whether to propose additional air regulations on dioxin emissions. However, such actions could be problematic and cause greater confusion, given that EPA’s proposed interim Preliminary Remediation Goals (“PRGs”) for dioxin in soils, which are based on a different set of toxicity values, have not been completed.
EPA’s press release also stated that “findings show that generally, over a person’s lifetime, exposures to dioxins do not pose a health risk,” and “EPA and its partner agencies do not recommend avoiding any particular foods because of dioxin.” EPA’s characterization of its findings, however, is inconsistent with the Agency’s stated intent to set stricter environmental limits and remediation standards for past releases at sites in its regulatory programs. EPA’s statement concerning the safety of foods also runs contrary to the risk estimates that emerge from the application of the new RfD to the recently updated United States Department of Agriculture (“USDA”) Dietary Guidelines for Americans. Simply stated, Americans would substantially exceed EPA’s RfD merely by consuming foods in accordance with USDA’s daily dietary recommendations. This result could have the unintended consequence of scaring people away from eating a healthy, balanced diet. Hence, EPA appears to want to have it both ways – a very stringent RfD for its regulatory programs while at the same time reassuring people that they “should continue to eat a balanced diet and follow the 2010 Dietary Guidelines” despite the risk of exceeding the dioxin RfD.
EPA’S METHODOLOGY IN PERFORMING ITS NON-CANCER ASSESSMENT IS CONTROVERSIAL
In addition to the many technical criticisms of commenters on the science on which the non-cancer assessment is based, critics also contend that EPA overreached in extending the application of the TCDD RfD to the other PCDDs, PCDFs, and cPCBs through the use of Toxicity Equivalence Factors (“TEFs”). Under the TEF approach, the toxicity of these other compounds is purportedly correlated to the toxicity of the TCDD reference compound. In the 2010 draft version of the EPA Reanalysis of Key Issues Related to Dioxin Toxicity and Response to NAS Comments, which was released for public comment and review by the EPA Science Advisory Board (“SAB”), TEFs played a minor role and were only discussed in the context of considering the background levels of these other compounds in the scientific studies that EPA had evaluated in its analysis.
However, in the Reanalysis Volume 1, the consideration of TEFs plays a prominent role. EPA’s inclusion of new language in the Executive Summary and in Chapter 1 of the main text greatly expands the application of the non-cancer assessment beyond TCDD to the other so-called dioxin-like compounds (“DLCs”). This new language was not peer-reviewed by the SAB Dioxin Review Panel, an expert panel of scientists knowledgeable about technical issues related to dioxins and risk assessment. Rather, it was interjected by EPA after the SAB review. EPA’s actions are contrary to its stated goal of increased transparency, and are likely to subject the Agency to much criticism, and a possible legal challenge.
EPA’s issuance of the non-cancer portion of its dioxin reassessment likely will significantly impact many aspects of American industry and agriculture. Despite EPA’s finding that “exposures to dioxins do not pose a health risk,” EPA’s establishment of a strict 0.7 pg/kg-day RfD may result in more stringent environmental remediation standards, both when establishing original cleanup levels and when evaluating a site’s progress at its five-year review. Further, EPA’s inclusion of DLCs in the non-cancer assessment subjects the Agency to much criticism and potential legal challenges.