The California Office of Environmental Health Hazard Assessment (OEHHA) has issued a Notice of Intent to list welding fumes as a chemical known to the State of California to cause cancer under Proposition 65, formally known as the Safe Drinking Water and Toxic Enforcement Act of 1986. The proposed listing is being made through the Labor Code mechanism, which authorizes OEHHA to add substances identified as carcinogens by authoritative bodies referenced in California’s Labor Code. Following its determination that welding fumes meet the criteria for listing, OEHHA initiated a public comment period prior to formally adding welding fumes to the Proposition 65 list.
Proposition 65 requires businesses operating in California to provide clear and reasonable warnings before exposing individuals to chemicals known to cause cancer, birth defects, or other reproductive harm. The law applies broadly to manufacturers, distributors, retailers, employers, and property owners when exposures exceed established safe harbor levels. Although Proposition 65 is most commonly associated with consumer products, its requirements also extend to occupational and environmental exposures. As a result, the proposed listing of welding fumes could have significant implications for industries where welding activities are prevalent, including manufacturing, construction, metal fabrication, shipbuilding, automotive production, and maintenance operations.
OEHHA’s proposal is based largely on findings from the International Agency for Research on Cancer (IARC) Monographs Volume 118, Welding, Molybdenum Trioxide, and Indium Tin Oxide. In this comprehensive review, IARC evaluated epidemiological studies, animal studies, and mechanistic evidence related to welding exposures. The agency concluded in 2018 that welding fumes are carcinogenic to humans (Group 1), upgrading their previous 1989 classification of “possibly carcinogenic to humans” (Group 2B). IARC found sufficient evidence that welding fumes cause lung cancer and reported positive associations with kidney cancer. The monograph also classified ultraviolet radiation generated during welding as a Group 1 carcinogen. With welding activities occurring across a broad range of industries, these findings underscore the importance of effective workplace health protections and regulatory compliance.
If welding fumes are formally added to the Proposition 65 list, businesses may face new compliance obligations related to workplace exposures, warning requirements, contractor and visitor notifications, and potential enforcement actions. Companies with welding operations may need to evaluate employee, customer, and bystander exposures, review existing exposure control programs, and determine whether Proposition 65 warnings or other risk management measures are warranted. Proactively assessing these issues can help organizations reduce regulatory risk, avoid costly litigation, and demonstrate a commitment to worker health and safety.
As California continues to expand the Proposition 65 chemical list, understanding potential exposure risks and compliance obligations is becoming increasingly important for businesses. RHP Risk Management helps companies navigate the complex requirements of Proposition 65 through exposure assessments, toxicological risk evaluations, warning determination analyses, product and workplace compliance reviews, expert witness support, and regulatory consulting. Whether your organization manufactures products, operates industrial facilities, or manages workplace exposure risks, RHP can help you understand and address Proposition 65 requirements. Contact RHP Risk Management at (866) 481-8188.