Health-based Recommendations to Address Potential Cancer Risks to Occupational Bystanders from the use of 1,3-D

ANNOUNCEMENT: New Regulations Effective January 1, 2026

Restrictions on 1,3-Dichloropropene (1,3-D) to protect occupational bystanders

New regulations developed jointly and mutually by the California Department of Pesticide Regulation (DPR) and the Office of Environmental Health Hazard Assessment (OEHHA) take effect January 1, 2026 to restrict the use of the pesticide 1,3-D to address cancer risks to occupational bystanders, including farmworkers. The new regulations establish enhanced buffer zones and require ongoing evaluation of exposure risks. The regulations build on recent protections for residential bystanders developed by DPR that went into effect in January 2024.

More information on 1,3-D use restrictions and reduction in emissions: DPR and OEHHA to Advance Regulations to Restrict 1,3-D Use in California.

UPDATE: Comments from the external peer reviewers are now available for download below.

Under the authority of California Food and Agricultural Code Section 12980 and 12981, OEHHA prepared health-based recommendations for the Department of Pesticide Regulation (DPR) to address potential cancer risks to occupational bystanders from the use of the fumigant 1,3-dichloropropene (1,3-D). On June 11, 2024, OEHHA submitted a memo as well as an attachment that included the preliminary analyses and further assumptions underlying the risk calculations. OEHHA also submitted a supplemental document that supported the memorandum. OEHHA requested external scientific peer review of the scientific basis of the memo and its associated documents, per the requirements of California Health and Safety Code section 57004. Comments from the peer reviewers are available for download below.

On November 14, 2024, DPR proposed new regulations, developed jointly and mutually with OEHHA, to mitigate the cancer risk from 1,3-D to occupational bystanders. Public comments were accepted by DPR until January 24, 2025. Public hearings on the proposed regulations were held in various locations early in 2025. The joint press release related to this comment period and the hearings is available on both DPR and OEHHA’s websites.  

On June 5, 2025, DPR announced an update to the regulations developed jointly and mutually with OEHHA. Public comments can be submitted to DPR until June 20, 2025. 

For more information on the proposed amendments pertaining to the restricted use of 1,3-Dichloropropene (1,3-D) to mitigate the potential 40-year working lifetime cancer risk to occupational bystanders, go to DPR’s webpage on 1,3-D.