The California Department of Pesticide Regulation released a draft regulation on Tuesday to further restrict use of the fumigant 1,3-D, known by the brand name Telone.

1,3-D is a pre-plant fumigant used to control insects, nematodes, and other organisms in the soil that threaten a variety of crops including nut trees, berries, sweet potatoes, and grapes. It is commonly injected into the soil or applied through drip irrigation.

DPR released a draft regulation to further restrict the use of 1,3-D, following brief spikes in air monitor readings last year. The measures include tarping, deeper injections and expanded buffer zones.

The proposed regulations would strengthen restrictions on use and significantly reduce potential residential and non-occupational bystander exposure to one of the most highly used agricultural pesticides in California, 1,3-D. The pesticide 1,3-D has been linked to potential acute and cancer health effects at certain levels of exposure, according to DPR

“Reducing human health risks from 1,3-D exposure is a priority for the state,” said DPR Director, Julie Henderson. “Taking action to strengthen restrictions on the use of 1,3-D to lower those risks is core to our mission of protecting human health and the environment.” 

DPR’s proposed regulations require the use of totally impermeable film (TIF) tarpaulins or alternate mitigation measures that provide a comparable degree of protection – such as deeper soil-injection

The department conducted a pilot project in 2020–21 with pesticide applicators and local county agricultural commissioners to help develop alternative mitigation measures that better protect public health and additionally provide growers with compliance options that satisfy DPR’s strict regulatory requirements. DPR conducted the pilot project in regions where communities requested localized studies as part of their AB 617 Community Emissions Reduction program.

The proposed regulations would expand setbacks from occupied structures, limit application rates, acreage, and allowed application methods, and include more stringent use requirements between November to February when weather conditions can create higher air concentrations following an application. The regulations also propose requirements for lower-emission application methods for tree and vine applications, which have the highest application rates for 1,3-D.

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 DPR says the proposed regulations will address both potential cancer and acute health risks to non-occupational and residential bystanders from 1,3-D use, based on a health-protective regulatory target established last year after consultation with state and local agencies. In addition to these actions, DPR is currently working on separate regulations to address risks to workers from potential exposure to 1,3-D.

The mitigation measures proposed in the regulations are more health-protective than the current township cap program that limits 1,3-D use in the state. 

 DPR is accepting public comment on the regulations between Nov. 18 and Jan. 18 at 5 p.m. Comments can be submitted via U.S. mail or via email to, or by FAX at (916) 324-1491. Find more information on the 1,3-D regulations on DPR’s website, including information on a public hearing scheduled for Jan. 18.  

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