IRIS Assessments Continue for Methanol, MTBE, ETBE, Acrylonitrile

U.S. Environmental Protection Agency (EPA) announced its plan to address the four draft Integrated Risk Information System (IRIS) assessments that were placed on hold in June 2010, pending a review of some of the underlying studies relied on in the assessments. The four assessments were for methanol, methyl tertiary-butyl ether (MTBE), ethyl tertiary-butyl ether (ETBE), and acrylonitrile.

EPA put the assessments on hold because of a report written by the National Toxicology Program (NTP), a program administered by the National Institute of Environmental Health Sciences (NIEHS). The report outlined a review of research completed by the Ramazzini Institute, a lab in Italy that conducts animal testing to evaluate the potential cancer-causing effects of chemicals. The report recommended that further pathology reviews be carried out to resolve differences of opinion between NTP scientists and the Ramazzini Institute in the diagnoses of certain cancers reported in the study.

EPA and NIEHS have decided to jointly sponsor an independent Pathology Working Group (PWG) review, in cooperation with the Ramazzini Institute, of selected studies, including the methanol cancer assessment study. The review has begun and will continue over the next several months. The results will be made public and the cancer assessment for methanol will remain on hold until its completion.

The Ramazzini Institute diagnosed leukemias, lymphomas, or tumors in studies of MTBE and ETBE, and acrylonitrile. Based on other available data, EPA has determined that reliance on Ramazzini Institute study results is not necessary to continue with assessment development for MTBE, ETBE and acrylonitrile, including an assessment of cancer risks. Therefore, work on the assessments for the three chemicals will continue during the PWG review. When the four assessments (methanol, MTBE, ETBE, acrylonitrile) were put on hold in June 2010, two completed and publicly posted assessments (vinyl chloride and 1,1-dichloroethylene) were also identified as relying substantially on Ramazzini data. EPA plans to evaluate the results of the PWG review to inform conclusions about Ramazzini Institute tumor findings for these two assessments.

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