California, a leading agricultural state, faces ongoing concern over pesticide exposure. Levels of exposure have been measured to be higher among residents in agricultural areas, but measures of personal inhalation exposure to a wide range of pesticides are lacking.
Researchers at the University of California at Davis worked with Lindsay-based Californians for Pesticide Reform and community members in the San Joaquin Valley on a project to measure a wide range of pesticides using personal air samples. The project was funded by the California Air Resources Board’s Community Air Grants program.
Pesticides are by design toxic to target organisms and have been found to be associated with a number of adverse human health effects. When pesticides are sprayed on fields, there is both a primary drift on the day of the application as well as secondary drift in the days that follow resulting from volatilization and processes such as wind erosion, movement of soil particles and particle-associated pesticides from wind.
Adult and school-aged participants were recruited from small agricultural towns in the San Joaquin Valley. Thirty-one adult and 11 school aged participants were recruited, and sampling occurred on a total of 92 days.
Air samples were collected in backpacks used by participants
Participants wore a backpack sampler for 8 to 14 hours on 1-3 days. Samples were collected on two tubes, one with Tenax-TA resin and the other with XAD-2 resin. 21 pesticides were analyzed in total, using both LC/MS and GC/MS methods.
The results revealed detectable levels of pesticides in a significant proportion of participants’ samplers. Specifically, 22% of adults and one school-aged child had measurable levels of at least one pesticide in their samplers, including compounds such as 1,3-dichloropropene, chlorpyrifos (despite its banned status in California), pyrimethanil, buprofezin, and penthiopyra.
- 1,3-dichloropropene, listed as a carcinogen in California under Proposition 65 and classified as a likely human carcinogen by the US EPA. There are active efforts to reduce use in California.
Chlorpyrifos is clearly demonstrated to have a number of adverse health effects, and as a result, tolerance levels on food products have been revoked nationwide. It was banned for use in California in 2021, with the exception of granular formulations. The most recent EPA risk assessments considers both AChE inhibition and potential for neurodevelopmental effects as the primary endpoints of concern.
While the toxicity of the other compounds has been less studied, there is the potential for adverse health impacts.
- Developmental toxicity has been observed in both rats and mice for the fungicide pyrimethanil. Also of concern is the potential for endocrine disruption. A study in zebrafish found altered expression of genes related to the endocrine system, as well as oxidative stress.
- Buprofezin, an insecticide that acts on immature insect developmental stages has been found to cause malformations in embryos of catfish larvae. The compound has also been tested in mice and human cell lines.
- Penthiopyrad, a fungicide and the least studied of the detected compounds, warrants further investigation due to preliminary findings of developmental and metabolic disruptions in zebrafish models.
With the new notification regulation, we will have the opportunity to measure personal exposure when we know pesticides are being applied. It’s critical to take the guesswork out of monitoring and to measure real exposure.” Jane Sellen, Californians for Pesticide Reform.
Dr. Deborah Bennett, PhD, Public Health Sciences, University of California, Davis, emphasized the urgency to expand the scope of pesticide monitoring efforts. "Our findings underscore the need for broader surveillance of pesticide exposure. Current measures are insufficient to capture exposure to several compounds with documented toxicological risks," noted Dr. Bennett.
"This study underscores the prevalence of pesticide exposure in agricultural communities," remarked Angel Garcia of Californians for Pesticide Reform. "It highlights the imperative for rigorous monitoring and regulatory action to safeguard public health."
This study suggests the need to expand which pesticides are measured as personal exposure is occurring for compounds not regularly measured, and that for some of these compounds, the existing literature indicates the potential for toxicity. In addition, the state is currently developing a system of pesticide notification, expected to take effect in 2025, which will guide future personal air monitoring efforts.
“We have reason to believe that the high level of exposure documented in this study is actually an under-count,” said Jane Sellen of Californians for Pesticide Reform and the community PI on the study. “For too long, applications of hazardous chemical pesticides have been a closely guarded secret. With the new notification regulation, we will have the opportunity to measure personal exposure when we know pesticides are being applied. It’s critical to take the guesswork out of monitoring and to measure real exposure.”