Effective July 17, 2026, the Office of Environmental Health Hazard Assessment (OEHHA) is adding welding fumes to the list of chemicals known to the State of California to cause cancer under the Safe Drinking Water and Toxic Enforcement Act of 1986, sections 25249.5 et seq. of the Health and Safety Code, otherwise known as Proposition 65. Businesses should evaluate their operations to determine if welding fumes are present and if warnings should be posted.