Ten percent of children and 22 percent of adults in California's San Joaquin Valley may be breathing in detectable levels of pesticides.
In a small survey of adults and children across the three small agricultural towns in the San Joaquin Valley, a significant proportion were found to be exposed to at least one pesticide in the air they breathed, according to new research in the Journal of Exposure Science and Environmental Epidemiology.
One of these detected pesticides, named chlorpyrifos, is not even allowed to be used in California anymore, due to it having been linked to neurological damage in children.
"Although the cohort in our study was small, the findings are significant because they show children and adults in agricultural regions of the San Joaquin Valley of California continue to be exposed to pesticides and herbicides. This is despite efforts to decrease their use," study co-author Deborah H. Bennett, professor of environmental health at the UC Davis School of Medicine's Department of Public Health Sciences, said in a statement.
Pesticides are chemicals used to eliminate or control pests in agriculture, homes, and gardens. While they play an important role in protecting crops, some of them can also pose significant health risks to humans, especially when there is prolonged exposure. California alone uses millions of pounds of chemical pesticides in its agricultural industry, and five of the six most heavily pesticide-using counties—Fresno, Kern, Tulare, San Joaquin and Madera counties—are in the San Joaquin Valley.
In the paper, the researchers describe how they gave 31 adults and 11 children special backpacks to wear for 1-3 days, for eight to 14 hours each day. These backpacks had tubes to sample the air wherever the person was, enabling the researchers to determine the levels of pesticides that they were breathing.
"Twenty-two percent of adult participants had detectable levels of at least one pesticide. Two pesticides with established toxicity, 1,3-dichloropropene and chlorpyrifos were detected, along with first-time measurements of pyrimethanil, buprofezin and penthiopyrad in the United States, which all have potential indications of toxicity," the researchers wrote in the paper.
According to the U.S. Environmental Protection Agency (EPA), the long-term effects of pesticide exposure depend on the type of pesticide. Organophosphates—which include malathion, chlorpyrifos and diazinon—have been associated with cognitive deficits, memory problems, and neurodegenerative conditions such as Parkinson's disease. Organochlorines like DDT have been linked to an increased risk of cancers, particularly breast cancer, and may also interfere with hormone function, leading to reproductive and developmental issues.
The International Agency for Research on Cancer (IARC) has classified some pesticides as probable human carcinogens, and pesticide exposure during pregnancy has been linked to birth defects, low birth weight, premature births, and developmental disorders in children.
Some of the pesticides detected by the researchers include chlorpyrifos, 1,3-dichloropropene (a "likely human carcinogen"), buprofezin, fungicides pyrimethanil and penthiopyrad, and herbicide trifluralin. While the effects of some of these pesticides like chlorpyrifos are well known, others like penthiopyrad have never been tested on mammals, so the full extent of their effects on people is unknown. Penthiopyrad was previously found to cause developmental deformities in zebrafish, however.
"We need to expand community measuring and monitoring of chemicals routinely used in agriculture," Bennett said. "New studies are also needed to evaluate the potential toxicity of the chemicals people in California's agricultural communities are routinely exposed to."
The sample size in this study was very small, however, so more research is needed to fully back up these findings.
"Even with a small sample size, the results were alarming but not surprising," study co-author Jane Sellen from Californians for Pesticide Reform, said in the statement.
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References
Bennett, D. H., Sellen, J., Moran, R., Alaimo, C. P., & Young, T. M. (2024). Personal air sampling for pesticides in the California San Joaquin Valley. Journal of Exposure Science & Environmental Epidemiology. https://doi.org/10.1038/s41370-024-00708-4
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