Statement From the California Department of Pesticide Regulation on 1,3-D Monitoring Data and Regulatory Review

The California Department of Pesticide Regulation (DPR) released 2025 air monitoring data showing that annual concentrations of 1,3‑dichloropropene (1,3‑D) at the Parlier monitoring site reached 0.35 parts per billion (ppb), which is above DPR’s 0.27 ppb monitoring threshold, specifically designed to initiate further scientific review and evaluation.

California’s 2024 1,3‑D regulations were built for situations like this. When monitoring data exceed the monitoring threshold, DPR is required to — and already has — initiated the follow‑up evaluation to verify the regulations are working as anticipated. That analysis is currently underway and will be included in DPR’s 1,3‑D Annual Report, which will be released this fall as required by regulation. This comprehensive analysis includes examination of air monitoring trends, use data, and — where air concentrations are higher than expected — a description of actions DPR will take to address the high levels.

DPR publishes preliminary monitoring and pesticide‑use data on a quarterly basis to allow for greater public access and transparency. The 2025 data was posted as part of this routine process.

At this time, the DPR-established health‑based thresholds have not been exceeded. The air monitoring results from the Parlier site show concentrations above DPR’s monitoring threshold designed for ongoing regulatory review — not a finding of an immediate health risk.

DPR remains committed to transparency, public health, and ensuring California’s pesticide regulatory system continues to be protective, science‑driven, and responsive. Agricultural communities have real and understandable concerns about pesticide use and potential health impacts. We take those concerns seriously, and as the evaluation proceeds, DPR will communicate its findings publicly and to impacted communities.