The National Research Council, which spent more than 15 months reviewing EPA's draft, agreed with EPA's conclusions. The draft review, which began in 2008, was part of EPA's process of updating information on perc for its Integrated Risk Information System (IRIS), a database of human health effects resulting from exposure to various substances.
Classifying perc as a likely human carcinogen would place it in the second highest of five categories under EPA's cancer assessment guidelines. The highest risk category is “carcinogenic to humans.” Under previous EPA guidelines, perc was considered in between a “possible” and “probable” cancer risk.
The review panel, appointed by the National Academies, consisted of 20 members, mainly from universities. It raised concerns about the approaches the EPA used to evaluate data. The evidence “supports EPA's conclusion that tetrachloroethylene is likely to be a human carcinogen” but the panel debated which type of tetrachloroethylene-related cancer – leukemia, liver tumours, or kidney cancer - provided the strongest data for EPA to calculate its cancer risk estimation. For consistency, the panel recommended that EPA should develop a single model that integrates elements of all three models.
