The International Agency for Research on Cancer (IARC), the cancer agency of the World Health Organization (WHO), has evaluated the carcinogenicity of two types of per- and polyfluoralkyl substances—perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS)—and classified them as “carcinogenic to humans” (Group 1) and “possibly carcinogenic to humans,” (Group 2B) respectively.

PFAS are often called “forever chemicals” due to their indefinite persistence in the human body and the environment, as they take a very long time to degrade and build up over time. In recent years, their pervasiveness in drinking water has been noted by experts in the UK, the U.S., and globally, and the body of evidence regarding their harms to human health has grown. PFAS, including PFOS and PFOA, have been used in non-stick and stain-resistant consumer products, such as cookware, as well as in food packaging. However, some state and national governments are beginning to restrict or ban the use of certain PFAS, and some companies are beginning to voluntarily phase them out from products.

At an IARC meeting that took place November 7–14, 2023 in Lyon, France, a working group of 30 international experts spanning 11 countries thoroughly reviewed published literature on PFOA and PFOS, resulting in the classification of PFOA as “carcinogenic to humans” (Group 1) and PFOS as “possibly carcinogenic to humans” (Group 2B).

PFOA is carcinogenic to humans on the basis of sufficient evidence for cancer in experimental animals and strong mechanistic evidence (for epigenetic alterations and immunosuppression) in exposed humans. There was also limited evidence for cancer in humans (renal cell carcinoma and testicular cancer) and strong mechanistic evidence in human primary cells and experimental systems (for epigenetic alterations and immunosuppression, as well as several other key characteristics of carcinogens).

PFOS is possibly carcinogenic to humans on the basis of strong mechanistic evidence across test systems, including in exposed humans (for epigenetic alterations and immunosuppression, as well as several other key characteristics of carcinogens). There was also limited evidence for cancer in experimental animals and inadequate evidence regarding cancer in humans.

IARC noted that the general population that does not work with PFOS and PFOA in industrial contexts are mainly exposed to the chemicals by consuming food and drinking water, and acknowledged that PFOA and PFOS are ubiquitously present in the environment, even in the most remote areas.