Pesticide Exposure in the San Joaquin Valley
From The Common Knowledge Project, the free reference archive
What personal air sampling shows, what pesticide detection cannot establish, and where residents can find information.
What it is
Pesticide exposure means contact with a pesticide, through routes including breathing airborne material. Exposure, the amount absorbed into the body, and resulting illness are different questions. A detection establishes the presence of a measured chemical in a sample; it does not by itself establish injury.
Pesticides can leave an application site during spraying or afterward. DPR defines drift as movement away from the intended target, including spray or gas. EPA distinguishes post-application volatilization from spray drift and identifies chemical properties and weather among the factors affecting it. These pathways explain how exposure can occur beyond the treated crop; identifying a particular source requires additional evidence. DPR guide, p. 4, EPA explanation.
Why it matters
Workers and neighbors need information about conditions they do not individually control. For the CKP, this raises the question of Externalization: which precautions, exposures, and costs remain with people outside the pest-control transaction?
That question requires separate evidence about use, exposure, health effects, and responsibility. Neither a permit nor a detection settles all four. San Joaquin Valley Air Quality also concerns airborne pollution, but ordinary ozone and particle measurements cannot substitute for measurements of particular pesticides.
How it works in practice
Bennett and colleagues recruited 31 adults and 11 school-aged children in agricultural towns in Fresno, Tulare, and Kern counties. Sampling in 2021-2022 covered 92 participant days. Seven adults and one child had detectable pesticides in personal air samples. The paper appeared online September 10, 2024, in a May 2025 journal issue. Original study.
The sample was not a representative survey of Valley residents. Short sampling periods and detection limits constrain what it captures. It does not establish population prevalence, health effects at the measured concentrations, or which application produced a detection.
Chlorpyrifos was among the detections. California ended most agricultural uses after December 31, 2020, while retaining a limited granular-product exception. Detection therefore does not itself demonstrate unlawful spraying. DPR's 2019 agreement.
Residents can consult SprayDays California for intended restricted-material applications in production agriculture. It does not cover every pesticide. Locations appear as one-square-mile sections, and notified applications may change or never occur. Notices are information about plans, not measurements of exposure. DPR explanation, June 25, 2026.
Suspected pesticide incidents can be reported through the county agricultural commissioner reporting route. A report starts an investigative process; it is not a confirmed finding.
What they say vs. what's true
| What they say | What's true |
|---|---|
DPR presents permits, restrictions, enforcement, and notification as safeguards intended to protect workers and communities. DPR community guide. | Those safeguards are real interventions whose effectiveness requires evidence. Personal sampling adds information about what reaches people. Its limits also matter: notification, detection, source attribution, and demonstrated health harm answer different questions. |
Further reading
- Bennett et al., Personal air sampling for pesticides in the California San Joaquin Valley, online 2024; issue 2025.
- DPR, Pesticide Information for Farmworkers and Agricultural Communities, February 2025, printed p. 4; EPA, Pesticide Volatilization, 2026.
- DPR, Your Top SprayDays Questions, Answered, 2026.
See also
- San Joaquin Valley Air Quality, The Valley's ozone and particle pollution, its multiple sources, and what regional asthma research establishes. (cited by 2)
- Externalization, How a production decision can leave households and public systems carrying costs outside the transaction. (cited by 4)
- The Bill Comes Due in the Body, A field guide to who carries the health and environmental costs that do not appear in the price of what the Valley produces. (cited by 4)