On October 9, 2026, the Office of Environmental Health Hazard Assessment (OEHHA), under the California Environmental Protection Agency, announced a proposal to add the widely used herbicide Atrazine to the list of chemicals known to cause cancer under the Safe Drinking Water and Toxic Enforcement Act, commonly known as Proposition 65.
Background
As a broad-spectrum herbicide, Atrazine has long been extensively used for weed control in agricultural crops such as corn and sugarcane. Due to its widespread application and long residual period, its potential risks to the environment and human health have drawn continuous attention in the public health sector. Under California law, if the International Agency for Research on Cancer (IARC) identifies a chemical as a carcinogen, California is legally required to include it under the regulatory scope of Proposition 65. Following an assessment, OEHHA confirmed that Atrazine fully meets the statutory criteria for listing under California regulations.
Public Participation
To ensure a transparent and compliant decision-making process, OEHHA has opened a public comment period, which will close on November 9, 2026. Members of the public may submit their comments online via the website: https://oehha.ca.gov/comments
It is important to note that because this action constitutes a “ministerial listing,” the scope of public comments is strictly limited. OEHHA will only accept comments regarding whether IARC has sufficiently identified the chemical as a carcinogen to humans or animals. Scientific debates concerning the quality or weight of the evidence relied upon by IARC will not be considered.
Potential Impacts
If Atrazine is ultimately added to the Proposition 65, it will have far-reaching implications in California. Under the provisions of Proposition 65, any business operating in California whose products, premises, or emissions contain listed chemicals at exposure levels exceeding safe thresholds must provide a clear and reasonable warning to inform consumers or workers that the substance may cause cancer or reproductive toxicity. Warnings can be issued through various means, such as affixing labels to consumer products, posting signs in workplaces, distributing notices in rental residential complexes, or publishing announcements in newspapers. The requirement to provide warnings takes effect one year after a chemical is added to the list.
Furthermore, the Act explicitly prohibits businesses from knowingly and intentionally discharging listed chemicals into any source of drinking water during their operations within the State of California. Businesses must implement discharge control measures within twenty months from the date the chemical is listed to ensure full compliance with this prohibition.
All substances listed under Proposition 65 can be queried via ChemRadar GCIS:
https://www.chemradar.com/en/tools/cis/inv/64924a20e7fff39f787f1b0d?utm_medium=gcis&utm_campaign=cis
