Issue Date: September 12, 2011
Acrylonitrile, a major commodity chemical, is a building block for a vast array of polymer-based goods, from auto parts to carpeting to latex-free gloves used in health care.
But acrylonitrile is also likely to be carcinogenic to humans, says the Environmental Protection Agency. This is based on studies in laboratory rodents, according to the agency.
The general public could be exposed to this chemical by consuming food or water that comes in contact with plastic products or other polymers that contain residual acrylonitrile, according to an EPA draft assessment of the substance. People living near chemical plants that make or process the compound may also be exposed to acrylonitrile, says the draft, which the agency released in June.
But the acrylonitrile industry is rallying against the EPA draft assessment. The Acrylonitrile Group(ANG), an organization of North American producers of acrylonitrile and some companies that are major processors and users of the chemical, is leading the charge, saying the draft assessment “lacks scientific rigor and objectivity.”
As a result, ANG is now asking EPA to redraft its assessment so that it can add peer-reviewed studies the industry group wants included. In addition, ANG is requesting that EPA have a National Academies-like review done of the assessment.
EPA’s draft assessment would tighten the agency’s safe inhalation concentration for the chemical from the 2 μg of acrylonitrile per cubic meter of air set in 1991 to 0.9 μg/m3. This lower level is based on adverse nervous system effects from human exposure to the chemical—not on cancer risks.
In addition, the draft would break new ground by establishing a safe exposure limit for ingestion of acrylonitrile. The agency currently has no safe daily dose for oral ingestion of the chemical. The safe daily dose for acrylonitrile consumed in food or water would be 0.3 μg per kg of body weight per day, under the draft. This is based on noncancerous lesions found in the digestive tracts of laboratory rats exposed to the compound.
The safe inhalation concentration and the safe daily dose are scientific judgments, not regulations. However, they would factor into regulatory decisions such as air pollution permits for factories or cleanup standards for contaminated groundwater.
Air emissions of acrylonitrile from industrial plants are already regulated by EPA. In 1990, Congress listed acrylonitrile as a hazardous air pollutant in the Clean Air Act. According to the Toxics Release Inventory for 2009, the latest year for which full data are available, U.S. industrial facilities—almost all of them chemical plants—released about 374,000 lb of acrylonitrile to the air. Leading them was Ascend Performance Materials’ plant in Decatur, Ala., with 58,000 lb, followed by the Ineos facility in Lima, Ohio, with 49,000 lb.
But according to ANG Executive Director Robert J. Fensterheim, fear of tougher regulations is not what’s motivating industry to push EPA to alter the draft assessment on acrylonitrile. Its concern is about potential besmirching of the product.
“The implications of this in terms of the characterization of the chemical matters a lot to the industry even though there may not be a particular U.S. regulatory driver,” Fensterheim tells C&EN. “We’ve had a major global research program on this chemical for years.” This ongoing research effort is tied to product stewardship, he adds.
Formed in the 1970s, ANG has sponsored research on health effects of the substance and coordinated global product stewardship efforts, according to Fensterheim. Members of ANG are Ascend Performance Materials, Cornerstone Chemical, Dow Chemical, Ineos, and Saudi Basic Industries Corp.
ANG is particularly concerned with how EPA used data about workers exposed to acrylonitrile in part of the draft assessment that addresses cancer.
“Essentially all of the contemporary expert scientific reviews of acrylonitrile epidemiology (human) studies have concluded that there is not an association between real-world exposure to [acrylonitrile] and cancer,” the industry group said in a statement. ANG presented detailed scientific arguments critiquing the agency’s draft assessment during a five-hour public “listening session” held by the agency in August.
A major focus for ANG is EPA’s use of data from a 1998 epidemiology study of industrial workers exposed to acrylonitrile, which was conducted by National Cancer Institute researchers. The study concluded that workers’ exposure to acrylonitrile at the levels studied is not associated with an increased risk for most cancers. It also found no strong or consistent evidence for an association between exposure and cancer (Scand. J. Work Environ. Health,1998,24 suppl. 2, 25).
ANG wants to understand how EPA came to its hazard assessment, given the NCI study’s findings. The industry group is asking EPA to provide the underlying data and the computer codes needed to replicate the agency’s analysis. This, Fensterheim says, will provide greater understanding of EPA’s analysis and allow a check on the agency’s calculations. “We all make math errors,” he says.
What’s more, the industry group is also asking EPA to redraft the assessment, incorporating peer-reviewed studies selected by ANG. These publications are analyses and interpretations of other studies on acrylonitrile. ANG wants the agency’s assessment to address these reviews, which “provide perspectives at variance with the agency’s own analysis,” Fensterheim said in an Aug. 31 letter to EPA. “We are not advocating that EPA accept these interpretations, but ignoring their existence fails to provide a thorough, balanced review of all the available scientific information,” he wrote.
Such a redrafting of the acrylonitrile assessment would delay its completion, points out Sonya Lunder, senior analyst for the Environmental Working Group, an activist group. Industry demands that EPA include increasingly more information in its hazard assessments put a choke hold on the agency and slow adoption of new risk values for chemicals, she says.
EPA may resist redrafting the acrylonitrile document because of political pressure on its Office of Research & Development to speed up the glacial pace of its chemical assessments. Congress has held oversight hearings on this program over the past several years, most recently this summer (C&EN, Aug. 1, page 31). The Government Accountability Office, the investigative arm of Congress, has called for reforms of EPA’s chemical assessment program, which it continues to track. Agency officials, meanwhile, have pledged to pick up the pace of these analyses.
ANG is also asking for peer review of the assessment equivalent to those conducted by the National Academies. For acrylonitrile, the agency should not rely on its standard single-day, contractor-managed peer review of its chemical assessments, Fensterheim says.
“This is a very complex assessment,” he explains. It needs a review that allows plenty of time for reviewers to deliberate, he adds.
How EPA will respond remains unclear. Although the agency is under the gun to complete chemical assessments more quickly, no particular consumer or environmental group is pressing for EPA to finish the acrylonitrile assessment. The agency tells C&EN it has reviewed the studies ANG is promoting. EPA says it is releasing some additional data from the assessment as well. ◾
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