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April 24, 2023

What’s Next for the International Agency for Research on Cancer in 2023: Aspartame, Methyleugenol, PFOA, PFOS, and More


The International Agency for Research on Cancer (IARC), a specialized cancer agency of the World Health Organization (WHO), will hold its annual Monograph volumes this year. IARC’s Monograph is the WHO’s official program of hazard identification. IARC is holding three separate volumes (i.e., meetings) in 2023 to evaluate various chemicals for potential carcinogenic effects to humans.

  • Meeting 133: From February 28 to March 7, IARC assessed four chemicals: anthracene, 2-Bromopropane, butyl methacrylate, and dimethyl hydrogen phosphite. These agents are used to make dyes, drugs, plastics, pesticides, and other chemicals. See background information here and here. The working group classified anthracene, butyl methacrylate, and dimethyl hydrogen phosphite as possibly carcinogenic to humans (Group 2B). 2-Bromopropane was classified as probably carcinogenic to humans (Group 2A). The full scientific assessment will be published as Volume 133 of the IARC Monographs.
  • Meeting 134: On June 6 to 13, the agency will evaluate aspartame, methyleugenol, and isoeugenol. Aspartame is a very common product found in approximately 6,000 food products worldwide, including soft drinks, chewing gum, confections, gelatins, dessert mixes, puddings and fillings, frozen desserts, yogurt, tabletop sweeteners, and some pharmaceuticals such as vitamins and sugar-free cough drops. The global aspartame market stood at over US$380 million in 2022. Methyleugenol has been used as a flavoring agent in jellies, baked goods, non-alcoholic beverages, chewing gum, candy, puddings, relishes, and ice cream. Methyleugenol, along with isoeugenol, is also widely used as a fragrance ingredient in perfumes, toiletries, and detergents.
  • Meeting 135: On November 7 to 24, IARC will look at perfluorooctanoic acid (PFOA) — for the second time — and perfluorooctanesulfonic acid (PFOS). These two chemicals have been used to make nonstick cookware, water-repellent clothing, stain-resistant fabrics and carpets, some firefighting foams, and various products that resist grease, water, and oil.

IARC’s decision to review these chemicals is something companies whose products use these ingredients should pay attention to because, as recent history tells us, IARC decisions can have significant impact on companies’ products. For example, in March 2015, IARC classified glyphosate, the active ingredient in Monsanto’s Roundup™ brand of herbicides, as “probably carcinogenic to humans.” Notwithstanding the Environmental Protection Agency’s conclusion that there is no evidence that glyphosate causes cancer in humans, IARC’s classification spawned numerous lawsuits in several jurisdictions that are still ongoing.

But while Roundup is confined to certain herbicides used on farms, lawns, and gardens, IARC’s findings related to more ubiquitous chemicals, such as aspartame, has the potential for a much larger reach — aspartame alone is found in approximately 6,000 food products worldwide. And in the context of products liability litigation, it is possible for any party in the chain of manufacture and distribution — not just food and beverage companies, for example — to be included in potential lawsuits. As demonstrated by the ongoing Roundup litigation, IARC’s classification of these chemicals as carcinogenic poses a litigation risk, even in the face of more extensive, authoritative science on the safety of these agents.

In addition to being a potential catalyst for new litigation, IARC’s classifications can also impact existing litigation. For example, IARC already evaluated PFOA in 2016, finding that it was “possibly carcinogenic to humans.” But at that time, IARC only found “limited evidence in humans” for the carcinogenicity with respect to cancers of the testes and kidneys in heavily exposed individuals. Even so, IARC’s 2016 findings appear in class action complaints — for example, in litigation related to aqueous film forming foam (AFFF), a firefighting foam that often contained PFOA and is alleged to have contaminated drinking water1 — and in advertisements to broader audiences. And while the reasons behind IARC’s decision to revisit PFOA are not clear, it suggests that IARC could consider a new classification of carcinogenicity. Should IARC add additional cancers to its earlier Monograph volumes on PFOA or change the classification from the current “limited evidence in humans” finding, the updated classification could be cited by plaintiffs in ongoing PFOA litigation or incentivize entirely new suits altogether. Of course if IARC reverses course on PFOA, we could also see the opposite impact on litigation.

An IARC classification also comes with other ramifications outside of the courtroom. California’s Proposition 65 requires businesses to provide warnings about significant exposures to chemicals that cause cancer, birth defects, or other reproductive harm. California state law requires such notices for chemicals classified as carcinogenic, probably carcinogenic, or possibly carcinogenic by IARC.

How can companies who manufacture, supply, or produce these agents prepare for an IRAC Monograph and its potential fallout?

  • Industry players should begin assessing potential litigation risk by determining which of its products may be affected.
  • After understanding which products may be at issue, industry players should identify the potential user population. If, for example, the products are used by specialists who require licenses to use the products or patients who require a prescription, the litigation risk is very different compared to over-the-counter products that are used by the general population. The latter group may present more of a risk given both the lack of sophistication of the end user and the size of any potential group of plaintiffs.
  • It is also important to stay current on scientific literature and other regulatory determinations to determine the relative scientific probability of an IARC classification. Ultimately, IARC’s conclusion is just one agency’s determination and is certainly not the final word. For example, while IARC has concluded that glyphosate is “probably carcinogenic to humans,” the EPA and many regulatory agencies around the world have determined that glyphosate does not pose such a risk. Understanding the scientific landscape will help industry players evaluate IARC’s findings to assess whether they represent an outlier opinion or are based on an incomplete picture of the science.
  • Companies who work with these chemicals may want to consider participating in the IARC process. For Meeting 134, IARC is calling for interested parties to submit studies relevant to the carcinogenicity of aspartame, methyleugenol, and isoeugenol, with a closing date set for May 6, 2023. Separately, for Meeting 135, which evaluates PFOA and PFOS chemicals, IARC has set a call for data closing date on October 7 and a request for observer status (an opportunity to actually attend the Monograph) even sooner, on July 7. These deadlines are important because they allow interested parties to participate, and it is vital that IARC have all available data to make an informed decision.

Arnold and Porter’s diverse group of attorneys specializing in areas such as product liability, consumer products, life sciences, and food and beverage law have assisted companies with navigating the complexities associated with IARC’s classifications. Arnold & Porter will continue to monitor IARC’s actions pertaining to aspartame, methyleugenol, and isoeugenol, as well as PFOA and PFOS, and is prepared to leverage its vast wealth of knowledge to assist with the impact of IARC’s classifications.

Nate A. King contributed to this Advisory. Nate is a graduate of the Catholic University of America, Columbus School of Law and is employed at Arnold & Porter's New York office. Nate is admitted only in Washington. Nate is not admitted to the practice of law in New York.

© Arnold & Porter Kaye Scholer LLP 2023 All Rights Reserved. This Advisory is intended to be a general summary of the law and does not constitute legal advice. You should consult with counsel to determine applicable legal requirements in a specific fact situation.

  1. Third Amended Complaint, Bell et al. v. 3M Company et al., Case No. 1:16-cv-02351-RBJ, 2018 WL 5281374, at ¶ 38 (D. Colo. Oct. 5, 2018) (“The IARC concluded that there is ‘evidence’ of ‘the carcinogenicity of … PFOA’ in humans and in experimental animals, meaning that ‘&#91a&#93 positive association has been observed between exposure to the agent and cancer for which a causal interpretation is … credible.’”).