EPA hears critics of perc draft
Drycleaning industry representatives criticized the Environmental Protection
Agency’s new draft risk assessment for perchloroethylene during a one-day “listening session” held by the agency in August.
Addressed in the new draft are potential cancer and non-cancer human health
effects that may result from perc exposure. The draft is part of EPA’s process to update information on perc for the Integrated Risk Information
System (IRIS), which is used in risk assessments, decision-making and
regulatory activities.
The EPA document suggests that perc should be considered a likely human carcinogen, which would
place it in the second highest of five categories under EPA’s cancer assessment guidelines. If adopted, this ranking would represent an
elevation of EPA’s current official evaluation which places perc between a “possible” and “probable” cancer risk.
Paul Dugard, a toxicologist and director of scientific affairs for the Halogenated Solvents Industry Alliance, told EPA that “The draft IRIS document contains numerous examples of misreported results and
contrived and conservative interpretations.” The result, he said, is a series of harsh conclusions “that are not supported by the evidence” and that are “not founded in accepted scientific practices or… EPA’s stated policies.”
HSIA counsel W. Caffey Norman said the assessment “seems to take at face value studies that show an association between
perchloroethylene and adverse effects and to disregard studies that show no
such effects.”
Norman noted that the draft gives equal or more weight to community drinking
water studies with poorly characterized exposures that suggest a cancer link
than it does to the conclusions of independent reviewers that say human studies
do not constitute evidence for an increased risk of cancer resulting from
exposure to perc.
He contrasted the conclusions of the EPA draft with a perc assessment recently
approved by the European Commission’s (EC) Scientific Committee of Health and Environmental Risks of the Health and
Consumer Protection Directorate General which concluded that “no increases in risks from exposure to [perc] for any specific type of cancer,
including risks from liver and renal cancers, have been observed.”
Norman also expressed concern that EPA discounted the results from an
examination of existing worker populations, funded by HSIA and the Danish
Medical Research Council and completed in 2006.
Norman expressed dismay that the EPA “could discount such a carefully designed study, based on ‘potential biases,’ while emphasizing the results of lesser quality community drinking water
studies of mixed solvent exposure.”
Focusing on the draft’s evaluation of the animal data, Dugard commented that EPA’s use of the occurrence of mononuclear cell leukemia in laboratory rats as a
basis for quantitative risk assessment in humans is inappropriate. EPA’s data indicate that the model the agency used overestimates perchloroethylene
metabolism at low doses, in some cases by more than ten-fold, he pointed out.
EPA held the “listening session” so the public could offer preliminary thoughts on the draft assessment. The
written comment period ended Sept. 24.
Next comes a peer review by a panel convened by the National Academy of
Sciences. That is expected to take 15 months.
