A UC Davis Health study found that 22 percent of adults and 10 percent of children in an air quality study in California’s San Joaquin Valley were breathing detectable levels of pesticides. These include one chemical, chlorpyrifos, that is no longer permitted for use in California.
The new findings are published in the journal Journal of exposure science and environmental epidemiology.
“Although our study cohort was small, the findings are significant because they show that children and adults in agricultural regions of California’s San Joaquin Valley continue to be exposed to pesticides and herbicides despite efforts to reduce their use,” said Deborah H. Bennett, the study’s first author. Bennett is a professor of environmental health in the Department of Public Health Sciences at the UC Davis School of Medicine.
As a predominantly agricultural state, California uses millions of pounds of chemical pesticides.
According to data from the California Department of Pesticide Regulation, in 2022, five of the top six counties in California that used the most pounds of pesticides were in the San Joaquin Valley. These include Fresno, Kern, Tulare, San Joaquin and Madera counties.
The backpack sensors took samples of the air the participants breathed.
The researchers recruited 31 adults and 11 children living in three small farming towns in the San Joaquin Valley. They were given backpacks with two special air-collecting tubes on the shoulder straps. The placement of the tubes allowed the researchers to sample the air the participants breathed.
Each participant wore the backpacks for 1 to 3 days, 8 to 14 hours per day. The combined air sampling was conducted for a total of 92 days.
When researchers analyzed the results, they found that seven adults (22% of adult participants) and one school-aged child were exposed to detectable levels of at least one pesticide.
Pesticides detected by backpack sensors include:
- 1,3-dichloropropene, a pesticide used to eradicate parasitic worms
- Chlorpyrifos, a pesticide in use since the 1960s that has been linked to neurological damage in children
- Pyrimethanil, a fungicide used to prevent mold and mildew.
- an insecticide used to prevent insects.
- Penthiopyrad, a fungicide to prevent mold and mildew
- Trifluralin, a herbicide used to control grasses and weeds.
When the samples were collected, chlorpyrifos was no longer approved for use in California. Previous research had shown that chlorpyrifos has numerous adverse health effects, including acting as a developmental neurotoxin in children and sensitive populations.
Although the toxicity of compounds such as chlorpyrifos is known, others have not been sufficiently studied. For example, studies of penthiopyrad in zebrafish found that exposure to this chemical caused developmental deformities. However, no studies have been conducted on penthiopyrad in mammals, so the possible effects on humans are unknown.
“We need to expand community-based measurement and monitoring of chemicals commonly used in agriculture,” Bennett said. “Further studies are also needed to assess the potential toxicity of chemicals to which people in California’s agricultural communities are routinely exposed.”
Participants in this study acted as citizen scientists and performed their usual activities while using the backpacks to collect samples.
“Many people in farming communities are very concerned about pesticide exposure,” said Jane Sellen of Californians for Pesticide Reform, a co-author of the study. “They were happy to work with scientists to gather this much-needed data. Even with a small sample size, the results were alarming, but not surprising.”
Rebecca Moran, Christopher P. Alaimo and Thomas M. Young of UC Davis are also co-authors of the study.
The project was funded through the California Air Resources Board’s Community Air Grant (19-CAUP-11) and by the National Institute of Environmental Health Sciences (2P30 ES023513).