Industry Pushes Bad Science to Defend Carcinogen Chloroprene

This week, the EPA is hosting a two-day External Peer Review Meeting to get input on yet another iteration of an industry-sponsored mathematical model, sponsored by corporate polluters that are pushing the U.S. Environmental Protection Agency (EPA) to weaken its cancer assessment for chloroprene, a toxic petrochemical used to make neoprene.

EPA scientists and career staff in  the Agency’s Integrated Risk Information System (IRIS) program have conducted a rigorous and comprehensive evaluation of chloroprene health risks, that has been published, peer-reviewed, and fully vetted by industry and others. The IRIS evaluation classifies chloroprene as a LIKELY human carcinogen (EPA IRIS 2010), based on scientific evidence from government scientists at the National Toxicology Program (NTP), part of the National Institutes of Health (NIH). The NTP studies (NTP, 1998), also peer reviewed and fully vetted, demonstrate that chloroprene mouse and rat inhalation bioassays reported significantly increased incidence of neoplasms in liver, lung, forestomach, Harderian gland, mammary gland, Zymbal’s gland, kidney and the circulatory system in mice; and in the lung, mammary gland, thyroid, kidney, and the oral cavity in rats. These lab studies are the well-designed and controlled studies that are required by risk assessors to evaluate many chemical pollutants that are already poisoning our air, water, soil, homes, and workplaces – they are the evidence that should lead to environmental safeguards, before our communities are poisoned.

Denka Performance Elastomer LLC (Denka) is the only chloroprene producer in the U.S. Denka’s  factory in Louisiana’s notoriously polluted ‘Cancer Alley’ is a major driver of the cancer risks for the community residents—the highest cancer risks in the country (see NPR March 2018 for details).

Figure from ‘A Tale of Two Toxic Cities’ by Sharon Lerner, Feb 21, 2019).

With liabilities like that, Denka has only two choices, reduce its pollution, or deny that its pollution is harmful. (It could also start by denying that the pollution comes from its facilities, but as the only chloroprene producer in the nation, this is a rather uphill argument). In a 2011 NRDC report I co-authored, we called this the Four Dog Defense: My dog doesn’t bite; my dog bites but it didn’t bite you; my dog bit you, but it didn’t hurt you; my dog bit you, and hurt you, but it wasn’t my fault. Denka is on its second dog right now – deny that the bite of its dog will hurt. That’s where science-for-hire product defense firms like Ramboll come in.

For more on the Ramboll’s of the world, see Dr. David Michaels’ book, Triumph of Doubt: Dark Money and the Science of Deception (Oxford Univ Press, 2020). Corporate Crime Reporter describes it thus, “Exponent. Gradient. ChemRisk. Ramboll Environ. These are some of the companies that make up the product defense industry. Their jobmanufacture uncertainty on issues critical to public safetyissues like opioids, concussions, climate change, obesity, cancer, air and water pollution and worker safety.” (Corporate Crime Reporter, March 25th, 2020)

Denka’s interests are represented by Ramboll Environ, and its expert, Kenneth Mundt. He is the right person for the job, having previously defended chemical and tobacco industries. As a consultant for Philip Morris and the tobacco industry, Mundt attacked the National Cancer Institute’s findings that low-tar cigarettes could cause lung cancer (see 2016 investigative series by David Heath). On behalf of chemical manufacturers, Mundt has also defended formaldehyde (Mundt et al 2017), and defended chromium by withholding data from the Occupational Safety and Health Administration (OSHA) during its rulemaking process (Rick Weiss, Washington Post, Feb 24, 2006).

Ramboll has been like a child in its ‘terrible twos’ that just keeps saying ‘no, no, no’ in the face of all evidence to the contrary. The Ramboll (2020) model that is the subject of this week’s peer review meeting is just the latest version of a PBPK (physiologically based pharmacokinetic) model that Denka and Ramboll has brought to EPA multiple times. In 2017  Denka filed a ‘Request for Correction’ of EPA’s 2010 IRIS chloroprene assessment, asking for it to be withdrawn, the cancer classification of chloroprene to be downgraded from “likely” to “suggestive’” and the EPA exposure limit (called a Reference Dose, or RfD) to be replaced with Ramboll’s weaker one, about 150-fold less protective. In January 2018 EPA rejected Denka’s proposal in a 54-page response, identifying serious uncertainties and problems with the model. There were several more exchanges, with Ramboll re-submitting revised versions of the model, compelling the IRIS science staff to spend more time and resources to review it. In each case, IRIS staff identified problems and limitations.

Now, in the most recent round of product defense efforts,  Ramboll (2020) is proposing yet another version of its PBPK model. However, it has already been shown to be fatally flawed in the following ways:

  • The model makes presumptions regarding rodent-to-human metabolic extrapolations that are critical components of the PBPK model, but unsubstantiated by data (see Kaltofen, Nachman, and Hattis, 2020);
  • Ramboll’s model only works for lung cancer, overlooking all the other types of cancer that are likely caused by chloroprene (see NRDC comments);
  • Ramboll’s model integrates human lung cell metabolic information derived from only 12 people—9 men and 3 women—in a German study from the mid-1980s (Lorenz et al 1984), when Prince’s album Purple Rain was released. Importantly, cells sampled from 12 adults cannot possibly represent the U.S. national population, and even less so the predominantly African American population of ‘Cancer Alley’ (see NRDC comments).

In short, the Ramboll model introduces more uncertainty than it would address. EPA should not alter its IRIS chloroprene assessment, and certainly not weaken it in any way. If EPA uses Ramboll’s model at all, it should apply to all tumor types associated with chloroprene, and the entire evaluation should undergo the rigorous review process required of a full IRIS assessment.

In Cancer Alley and communities polluted by multiple petrochemical processing and manufacturing facilities, health risks are compounded by exposure to many chemicals. Across the country, the 3 top contributors to hazardous air pollution hotspots are chloroprene, ethylene oxide, and formaldehyde (Lerner, Feb 21, 2019). If EPA protected communities from these three chemicals, it would reduce the overall cancer risk from air pollution by 91 percent. For many of these communities—largely low-income communities of color—the cumulative cancer risks from just these three chemicals are hundreds of times above background. 

By continuing to fail to consider the cumulative impacts of exposures to multiple chemicals from multiple sources, including current exposures from legacy uses, EPA chemical assessments are failing to reflect the toxic reality that families suffer.

About the Authors

Jennifer Sass

Senior Scientist, Federal Toxics, Health and Food, Healthy People & Thriving Communities Program

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