The results are surprising given that they are inconsistent with decades of epidemiology studies, as well as the positions of regulatory agencies such as the Environmental Protection Agency.

In March 2025, the International Agency for Research on Cancer (IARC), a division of the World Health Organization, convened to finalize a review of the carcinogenic potential of automotive gasoline and various fuel additives. The IARC’s panel of 20 scientists from 16 countries classified—for the first time—gasoline as carcinogenic to humans due to, inter alia, evidence linking prolonged automotive gasoline exposure to urinary bladder cancer and acute myeloid leukemia. These conclusions stem from research and studies identifying increased cancer risks among individuals in professions with significant gasoline vapor exposure, including gas station attendants, refinery workers, tanker drivers and automotive mechanics. The results are surprising given that they are inconsistent with decades of epidemiology studies, as well as the positions of regulatory agencies such as the Environmental Protection Agency.

IARC classifies substances into one of the following groups: Group 1 (carcinogenic to humans); Group 2A (probably carcinogenic to humans); Group 2B (possibly carcinogenic to humans); and Group 3 (not classifiable as to its carcinogenicity to humans). These classifications have had widespread legal significance in the past—for example, IARC’s classification of glyphosate as a Group 2A substance in 2015 sparked mass litigation against Monsanto, the first company to develop and market glyphosate. In addition, if a substance is classified as Group 1 or Group 2, it is automatically considered carcinogenic under California's Proposition 65 law. Under this law, private citizens or organizations can receive bounties for filing lawsuits that allege products contain carcinogen levels exceeding the state’s safe harbor limits.

In addition to assessing automotive gasoline, the panel also assessed the carcinogenic potential of widely used fuel additives, including:

• Methyl tert-butyl ether (MTBE) and ethyl tert-butyl ether (ETBE): The panel categorized both MTBE and ETBE as possibly carcinogenic to humans due to findings from controlled studies that suggest carcinogenic properties of these additives. MTBE and ETBE are no longer added to gasoline in the United States, but these additives are currently used by countries in Europe and Asia, among others. The panel suggests that where these additives are still used, occupational exposure can occur in industries such as shipping, railroading and gasoline service.
• Tert-butyl alcohol, diisopropyl ether and tert-amyl methyl ether: The panel identified each of these additives as not classifiable as to their carcinogenicity in humans due to the insufficiency of available data. As greater data becomes available to the IARC, these additives may be elevated into the carcinogenic or possibly carcinogenic designations.

These findings reinforce the importance of evaluating safety protocols and regulatory compliance in industries where gasoline exposure is a concern. Companies engaged in fuel distribution, refining and retail operations should consider updating risk mitigation strategies, including enhanced ventilation systems, improved protective equipment protocols and proactive regulatory adherence.

Impacted organizations should consider seeking tailored legal counsel on risk management and compliance strategies.

For More Information

If you have any questions about this Alert, please contact Rosemarie DaSilva, Alicyn Craig, any of the attorneys in our Environmental Group, Phil Cha, Brad Thompson, Shelton M. Vaughan, Lindsay Ann Brown, David Amerikaner, any of the attorneys in our Energy Industry Group or the attorney in the firm with whom you are regularly in contact.

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