DPR and OEHHA to Advance Regulations to Restrict 1,3-D Use in California
The Department of Pesticide Regulation (DPR) and the Office of Environmental Health Hazard Assessment (OEHHA) are in the final stages of the rulemaking process for regulations to restrict 1,3-dichloropropene (1,3-D) use to address cancer risks for occupational bystanders.
If approved by the Office of Administrative Law (OAL), these regulations, developed jointly and mutually by DPR and OEHHA, would enact restrictions on 1,3-D use by January 1, 2026.
Specifically, the adopted regulations would require the following to reduce potential cancer risks for occupational bystanders:
- A minimum distance between 1,3-D application sites and people (called buffer zones), particularly farmworkers working in nearby fields. This adds additional setback requirements, building on previous regulations that require specific distances between 1,3-D application sites and homes and other occupied structures.
- That DPR continue to evaluate occupational risks associated with 1,3-D use and release a report annually on effectiveness of regulatory requirements. If necessary, and in consultation with OEHHA, DPR would be required to develop additional protections based on its annual evaluation of occupational risk. The annual evaluation would include an assessment of available data, assumptions and methods to estimate 1,3-D risk and, if necessary, update assumptions and methods to inform additional actions.
The regulations were proposed by DPR on November 14, 2024, and the initial 70-day public comment period ended in January 2025. DPR and OEHHA proposed modifications to the regulations and accepted additional public input during the modifications’ 15-day comment period that ended on June 20, 2025. DPR and OEHHA have reviewed all comments submitted on the modifications and are moving forward with the rulemaking package without further modification.
To view the text of modified regulations and the rulemaking package, visit DPR’s Proposed Regulations page.
The proposed regulations build on 1,3-D regulations that took effect on January 1, 2024, to address health risks for people who live near areas where applications occur, otherwise known as residential/non-occupational bystanders.
Further Evaluation for 1,3-D
Public comments received during the rulemaking process raised concerns about potentially conflicting or inconsistent assumptions, including combined near-field and regional ambient air concentrations of 1,3-D, the number of applications nearby, the length and time of potential exposure during a workday, and breathing rates for workers.
The current regulations rely on exposure assumptions currently available. However, DPR and OEHHA have begun conducting field studies to look at where and when fieldworkers are operating near 1,3-D applications and how fieldworkers move through fields over the course of a day through observational studies and interviews. These studies are in development and implementation collaboratively between OEHHA and DPR. Information gathered from studies will help inform future decisions about the potential for further mitigation or other regulatory action. This fall, DPR and OEHHA will convene roundtable meetings with community groups and other stakeholders to discuss preliminary results from the field studies.
Annual Report and Further Engagement
Consistent with current regulations, DPR is also working to release a draft annual report for 2024 that assesses 1,3-D exposure to residential/non-occupational bystanders. DPR currently reports quarterly on 1,3-D use across the state – and those reports will continue to be available on DPR’s website.
In early 2026, DPR and OEHHA intend to host a public workshop to share feedback and information gathered from the studies and roundtables and provide opportunity for public input.
Decreases in 1,3-D Emissions Since Regulations to Protect Residential Bystanders Went into Effect
DPR is tracking decreases in 1,3-D use over the last five years, including a 29 percent decrease in emissions due to changes in fumigation methods required by the 2024 regulations. The currently proposed regulations to add protections for occupational bystanders are expected to build on these decreases.
DPR and OEHHA Remain Committed to Identifying Reasonable Alternatives to Fumigant Pesticides
As an additional action on 1,3-D aligned with DPR’s work to foster sustainable pest management, DPR commissioned an independent study conducted by the California Council of Science and Technology on currently available, viable and effective alternatives to 1,3-D and other fumigants for managing pests in California. The study was released in March 2025, and additional information can be found on DPR’s website.
To stay informed, please sign-up for DPR’s “News” email distribution list on the department’s website: California Department of Pesticide Regulation.
ABOUT THE DEPARTMENT OF PESTICIDE REGULATION
The California Department of Pesticide Regulation’s mission is to protect human health and the environment. The department achieves this mission by fostering safer, sustainable pest management and operating a robust pesticide regulatory system. DPR’s work includes registering all pesticides sold or used in California, conducting pre- and post-registration scientific evaluations of pesticides to assess and mitigate potential harm to human health or the environment for pesticides in the air and water, and enforcing pesticide use laws and regulations in coordination with 55 County Agriculture Commissioners and their 500 field inspectors. DPR also conducts outreach to ensure pesticide workers, farmworkers and local communities have access to pesticide safety information. More information about DPR can be found on our website.
ABOUT THE OFFICE OF ENVIRONMENTAL HEALTH HAZARD ASSESSMENT
The California Office of Environmental Health Hazard Assessment is the lead state agency for the assessment of health risks posed by environmental contaminants. OEHHA’s mission is to protect and enhance the health of Californians and our state’s environment through scientific evaluations that inform, support and guide regulatory and other actions. As CalEPA’s scientific adviser, OEHHA works within CalEPA and across state government, with other state and federal agencies, businesses, community-based organizations, and Native American Tribes across California to develop actionable science that protects public health.
In addition to assessing health risks posed by chemicals, OEHHA develops data tools that support environmental health, performs outreach and education about pesticides and other chemicals, surveys exposure to harmful chemicals through Biomonitoring California, and assists in emergency response through expert consultation on matters related to chemical exposures.