Lindsay, CA. Pesticides continue to be pervasive in the air throughout California’s agricultural regions, according to the 2023 Air Monitoring Network Report released last month by the Department of Pesticide Regulation (DPR). Weekly samples collected at DPR’s four air monitors detected 19 different pesticides at trace or quantifiable levels and 8 pesticides at quantifiable levels, with 80% of samples including at least one pesticide detection. The four air monitors are located at schools in Oxnard, Santa Maria, Shafter and Watsonville. Pesticides were detected in more than 90% of the samples collected at Rio Mesa High School in Oxnard.
The Californians for Pesticide Reform (CPR) coalition notes with particular concern that detections of the fumigant pesticides chloropicrin and MITC are increasing, while levels of the carcinogenic fumigant pesticide 1,3-dichloropropene remain very high and the fumigant methyl bromide was detected in almost a third of the samples across the state – despite most uses of methyl bromide being internationally banned more than 20 years ago. All four fumigant pesticides were detected at all four monitoring sites.
1,3-dichloropropene:
Overall, 22% of the weekly air samples collected were contaminated with the toxic pesticide 1,3-dichloropene (1,3-D). Average concentrations of 1,3-D at each of the sites (long-term averages since DPR’s monitoring program began) are above the California Office of Environmental Health Hazard Assessment’s No Significant Risk Level, equivalent to an average concentration of 0.04 parts per billion. Air concentrations reached more than 13 times that level at the elementary school site in Shafter averaged over multiple years, and 4 times that level in 2023 alone.
OEHHA’s No Significant Risk Level for 1,3-D is what pesticide reform advocates say should be the one standard for all California residents. But DPR currently sets – and has announced no plans to change – the daily exposure target for children and residents at a level of 0.56ppb, which is fourteen times higher. This allows DPR to state in the recently released report that “pesticide concentrations found in the air are unlikely to be harmful to human health.”
Chloropicrin:
The report revealed a troubling increase in air concentrations of another hazardous fumigant, chlorpicrin. Chloropicrin is a potent eye and respiratory irritant, and is listed as a Toxic Air Contaminant (TAC) by the State of California. DPR has asked the companies that produce and sell chloropicrin to conduct follow up tests to evaluate whether or not this pesticide causes cancer because they decided that results from earlier studies aren’t clear.
In 2023, peak seasonal (13 week) air levels of the fumigant chloropicrin reached 95% of the subchronic screening level at the Oxnard monitoring site and 65.4% and 58.9% of this level at the Watsonville and Santa Maria monitoring sites. This level is set to prevent rhinitis, or nasal irritation. DPR says they are in the process of conducting a more detailed evaluation of chloropicrin use conditions but no target date for completing this review is provided.
MITC:
The report also revealed substantial increases in peak seasonal (13 week) air levels of MITC between 2022 and 2023 at Shafter and Santa Maria monitoring sites. MITC is the main breakdown product of two fumigant pesticides, metam sodium and metam potassium. It is a potent respiratory and eye irritant.
Methyl Bromide:
Of particular concern is the continued high frequency of detections of the fumigant pesticide methyl bromide. Because of its toxicity and its role in ozone depletion, methyl bromide was banned internationally with an intended phase-out by 2005. However, California agriculture continues to secure “critical use exemptions” which have kept use levels high – more than 1.6 million pounds in 2023. As a result, methyl bromide were detected at all four of the sites, with quantifiable levels at three of the four sites. Overall, methyl bromide was detected in more than 30% of the samples across all the sites – a staggering amount for a chemical that has been internationally banned for two decades for all uses except very limited fumigation of commodities before international shipment.
Cancer risk estimates:
It is deeply troubling to see that cumulative average air concentrations for 1,3-D at all four air monitoring network sites continue to exceed the OEHHA Cancer No Significant Risk Level (NSRL).
The chloropicrin reference concentration of 0.24 ppt for controlling cancer risk to the 1 in a million level was established by DPR and was supported in review by OEHHA and the TAC Scientific Review Panel. DPR subsequently made a unilateral decision that chloropicrin cancer data was equivocal and that an additional study was needed to assess cancer risk. The second phase of this study is currently in process after repeated delays. In the meantime, we are left with great uncertainty about the cancer risk from exposure to chloropicrin.
And finally, captan and malathion are both listed as carcinogens under Proposition 65, and OEHHA has set “No Significant Risk Levels” for both. Both were detected at quantifiable levels by at least one monitor. However, DPR’s list of six carcinogenic pesticides being monitored excludes both captan and malathion, and falsely states: “The AMN program monitors six pesticides that are designated as known or probable carcinogens by Proposition 65 or by US EPA’s B2 list” (bolding added.) In response to public comment by the CPR coalition calling for the inclusion of these two additional Prop. 65 carcinogens, DPR’s report states: “DPR is working on updating the AMN carcinogen list” and adds that “no action or changes are required for this comment” (Appendix J, p.16).
Cumulatively, these findings and omissions combine to grossly underestimate the level of cancer risk experienced at the four monitoring sites, all of them schools.
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Californians for Pesticide Reform (CPR) is a diverse, statewide coalition of 200+ member groups working to strengthen pesticide policies in California to protect public health and the environment. Member groups include public and children’s health advocates, clean air and water groups, health practitioners, environmental justice groups, labor, education, farmers and sustainable agriculture advocates from across the state.