California Proposes Adding Herbicide Atrazine to Proposition 65

On October 9, 2026, California’s Office of Environmental Health Hazard Assessment (OEHHA)—a branch of the California Environmental Protection Agency—proposed adding the widely used herbicide Atrazine to the state's Proposition 65 list of cancer-causing chemicals.

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 Comment Period

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 through the OEHHA Comments Portal.

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 on Businesses

If Atrazine is officially listed under Proposition 65, it will trigger two key regulatory requirements for businesses operating in California:

• Businesses whose products, facilities, or environmental releases expose individuals to Atrazine above safe harbor levels must provide clear warnings. These warnings can be delivered via product labeling, workplace signage, tenant notices, or published media. This requirement takes effect one year after listing.
• Proposition 65 strictly forbids businesses from knowingly discharging listed chemicals into sources of drinking water. Companies must implement control measures within 20 months of the listing date to ensure full compliance.

You can look up all chemicals regulated under Proposition 65 using the ChemRadar GCIS Database.

Further information

OEHHA