Conflicts of interest in the International Agency for Research on Cancer process of identifying carcinogenic hazards to humans

Managing conflicts of interest (COIs) in scientific decision-making is important for minimizing bias and fostering public trust in science. Proper management of COIs has added significance when scientists are making decisions that impact public policy, such as assessing substances for carcinogenicity. The International Agency for Research on Cancer (IARC) organizes expert working groups to identify putative carcinogens and determine whether or not the hazard is likely to present significant potential harm to humans. While IARC has policies for managing COIs, prior professional experience with the substance being assessed is not defined as a COI. Indeed, IARC working group members are chosen based on subject matter expertise, including prior publication on the substance under review. However, a person’s prior experience with a substance poses a significant potential COI by equipping them with strong pre-existing views about the substance’s toxicity and carcinogenicity. To minimize the risk of bias in IARC working groups, participants with voting powers should be independent scientific experts with sufficient professional experience to review carcinogenicity data but with no substantial prior experience with the substance under review. A related IARC practice restricting data review by working groups to selected publications is another significant COI. Instead, all accessible data should be available for consideration by working groups in assessing the carcinogenic hazard of substances. Another recommendation to reduce potential bias would be to reinstate the option of “probably not carcinogenic to humans”.