28
Oct
Organophosphate Pesticide Drift from Agricultural Fields Elevates Risk for Pregnant Farmworkers
(Beyond Pesticides, October 28, 2025) A California-based population study published in BMC Public Health finds that “7.5 [percent] of all pregnant people in California who gave birth in 2021 lived within 1 km [kilometer] of agricultural fields where OP pesticides [organophosphates] had been used during their pregnancy. . .†Despite a 54 percent decrease in overall use of the neurotoxic insecticide chlorpyrifos in the state between 2016 and 2021, after a statewide ban on the organophosphate insecticide in 2016, researchers found that in one California county, “more than 50 [percent] of pregnant people lived within 1 km of OP pesticide use.â€
Significant disparities were found in terms of elevated exposure to pesticides, “with Hispanic/Latine, young people, and residents of the predominantly fruit and vegetable growing Central Coast region being most likely to live near OP pesticide applications during pregnancy.†The authors suggest that “regulatory changes to limit use or restrict applications in close proximity to residential areas could have a substantial public health benefit on children’s brain development.â€
These findings add to the existing scientific literature on perinatal and maternal pesticide exposure associated with adverse long-term health effects for children and mothers. They also serve as a reminder to public health and environmental advocates of the importance of moving beyond individual pesticide bans and toward assessments of alternatives for non-synthetic solutions to pest management, including organic and least-toxic substances, as defined by federal law.
Background and Methodology
The researchers gathered data for agricultural OP pesticide use from the California Department of Pesticide Regulation’s (CDPR) Pesticide Use Reporting (PUR) program for datasets in 2016 and 2021. The OP pesticides for which data were gathered include: acephate, bensulide, chlorpyrifos, diazinon, dichlorvos, dimethoate, disulfoton, ethoprop, fenthion, malathion, methidathion, methyl-parathion, mevinphos, naled, oxydemeton-methyl, phorate, phosmet, tetrachlorvinphos, tribufos, and trichlorfon. OP pesticide spraying events were only recorded if they had a “valid location, application date, agricultural site, amount of active ingredient in the applied pesticide product, and acres treated…included†in the associated reports. PUR program data was cross-referenced with data from California Department of Water Resources’ (DWR) 2020 crop mapping dataset to “more accurately identify where the pesticides were likely applied.â€
In terms of data sets for assessing pregnant individuals’ proximity to OP use over the course of their pregnancy, “All pregnancies were treated as 40 weeks long when calculating the date of conception and address on the birth record was assumed to reflect residence throughout the entire pregnancy.” The authors continue: “The 1 km buffer zone around the residence was chosen to be consistent with a cohort study [conducted at UC Berkeley’s School of Public Health] which found associations between OP applications within 1 km of maternal address during pregnancy and reduced IQ in the children, and is a distance commonly used in other epidemiologic proximity studies in California [].â€
The authors are researchers at University of California, Berkeley, and the Public Health Institute. The funding for data analysis and manuscript writing was provided by Natural Resources Defense Council and Californians for Pesticide Reform, respectively. Additional funding was provided through the U.S. Centers for Disease Control’s (CDC) 2022 EH22-2202 cooperative agreement.
The following declaration was made in terms of “[e]thics approval and consent to participateâ€:
“This study was conducted in compliance with the Declaration of Helsinki’s requirements for secondary research on stored data. The study protocol and data handling were reviewed and approved by the California Health and Human Services Agency’s Committee for the Protection of Human Subjects— an Institutional Review Board (IRB) authorized by the United States Office of Human Research Protections (Federal wide Assurance #00000681). The IRB waived the need for consent to participate and determined that the project qualifies as “Not Research†under the US Federal Policy for the Protection of Human Subjects (the “Common Ruleâ€).â€
Results
The main results of this study highlight the power of policy when used effectively and the importance of pairing the prohibition or reduction of toxic chemicals with increased access to alternative chemical and non-chemical pest management solutions that align with natural and organic principles.
Firstly, there is a direct link between prohibition and decreased use of pesticides:
- “In 2016, the San Joaquin Valley region used the largest amount of agricultural OP pesticides (605,116 kg). OP pesticide use in the San Joaquin Valley reduced 9% from 2016 to 2021 following the cancellation of chlorpyrifos, with the largest reduction in Kern County (−87%).
- Large reductions in OP pesticide use were also seen in most other regions of California, ranging from −30.7% to −76.0%. Only the Central Coast region measured an increase (+0.5%) in agricultural OP use during this time. Two of the five counties in the Central Coast region reported an increase in total agricultural OP pesticide use from 2016 to 2021: Monterey County (+26%) and Santa Barbara County (+4%) (See Supplemental Table 2).
- In 2021, the areas with the highest intensity of OP pesticide use were in Monterey County and Santa Barbara County (Central Coast), Imperial County (Southern California), and Kings County (San Joaquin Valley). The OP pesticide use in these counties was highly concentrated with areas reporting an intensity of 6250–13,550 kg per township (9.6×9.6 km).â€
The 26 percent increase in OP pesticide use concerns public health professionals in the state, given previous research coming out of Monterey County that links maternal OP pesticide exposure to adverse effects on children. This includes a 2017 study published in Toxics by UC Berkeley researchers who found “residential proximity within 1 km of OP pesticide use during pregnancy was associated with lower IQ in children, with one standard deviation increase in total OP pesticide use near the home (237 kg) being associated with a 2-point decrease (15% of a standard deviation) in Full Scale IQ at age 7.†With more than half of all pregnant people in the county living within the identified elevated risk zone, researchers suggest “that a large population may be at increased risk of IQ decrements, autism, or other adverse neurodevelopmental impacts.†Â
The researchers conclude that “OP use and residential proximity remain high [despite a state ban] in the Central Coast region with lettuce, cole crop, and strawberry cultivation.†They also “suggest that agricultural transition to non-chemical production and/or pesticides that are not reproductive toxicants could reduce adverse prenatal exposures for a large population in the Central Coast region of California.â€
Previous Coverage + Updates
Organophosphate pesticide use has been linked to numerous adverse health effects highlighted in the scientific literature and recognized by various regulatory and international bodies, including the decision in May by United Nations’ Conference of Parties (COP) for the Stockholm Convention on Persistent Organic Pollutants (POPs) to move chlorpyrifos to Annex A (Elimination) with exemptions on a range of crops, tick control for cattle, and wood preservation, according to the POPs Review Committee. Chlorpyrifos is a highly neurotoxic organophosphate insecticide linked to brain damage in children. (See Daily News here.)
Researchers at UC Berkley, UC Merced, and Stanford University published a study in Environmental Research last year, finding that “early life organophosphate pesticide exposure has been linked with poorer neurodevelopment from infancy to adolescence.†Researchers in this study acknowledge that there is still much more to be done in furthering understanding of “neural mechanisms underlying these associations,†and yet there is “notable consistency†in their Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS) birth cohort study. (See Daily News here.) Studies have also linked organophosphate pesticide exposure to various other health effects, including elevated risk of inflammatory bowel disease (IBD), depression and suicidal ideation, women’s reproductive health dysfunction, rheumatoid arthritis, and disproportionate DNA damage for Latine children from rural farmworker families relative to children in urban, non-farmworker families.
The state of California is taking numerous steps to address the concerns of frontline communities; however, public health and environmental advocates, as well as farmworker-advocacy groups, continue to call for transformational policies and programs rather than mitigation that permits the continuous poisoning of communities living and working near agricultural fields, or who may come in indirect contact with synthetic chemicals through other pathways.
In March, the California Department of Pesticide Regulation (DPR) announced the launch of SprayDays California, “a first-of-its-kind statewide system designed to provide transparent, accessible and timely notifications and information about the use of specific pesticides[,]“ according to the agency’s press release. The state says that notification will occur in “advance of the scheduled use of California restricted material pesticides in production agriculture.†(See the Daily News here when the program was initially launched earlier this year.) On August 28, DPR updated the program by adding map-based sign-ups and additional visibility to highlight one-square-mile sections after public comments (including from farmworkers), which had at the time identified inadequate notice of pesticide use to those who work in or live in proximity to agricultural fields. (See Daily News here.) At the time, DPR shared that 3,700 users signed up for notification alerts; on the six-month anniversary of SprayDays, DPR issued a public release boasting a near identical figure in terms of total text and email sign-ups. This has been characterized as a lack of engagement by advocates who say it underscores the need to think about upstream solutions that get at the heart of the problem—a transition away from chemical-intensive practices.
Rather than focusing on individual responsibility to keep track of when chemicals are sprayed, frontline advocates are calling for more systemic change. In a recent interview published in The Urban Activist, Adam Scow—a music teacher in a school located near pesticide-intensive agricultural fields and lead organizer with the Campaign for Organic and Regenerative Agriculture—shares the importance of moving beyond toxic chemical reliance in addressing pesticide drift from Driscoll’s non-organic fields in Watsonville, California:
“There has been ongoing pressure for better notifications from Driscoll’s and farmers regarding the use of pesticides, along with certain restrictions—such as limiting applications to weekends at night. However, these measures do not adequately address the larger issue. The significant problem is the presence of these invisible gases in the environment. They can drift across the valley and remain in the air for up to 72 hours, or three days,†explains Scow. “There is no specific season; it is a continuous issue.â€Â
Call to Action
ATTEND TOMORROW’S WEBINAR—October 29, 2025, 1:00-3:30 pm (Eastern time, US)—on health protective practices that are cost-effective—Beyond Pesticides’ 42nd National Forum Series. This Forum will focus on aligning land management with nature in response to current chemical-intensive practices that pose a threat to health, biodiversity, and climate while bringing together scientists and land managers working to recognize and respect the ecosystems on which life depends. The virtual Forum is free to all participants. See featured speakers! Register here.
The Call to the Forum states:
We are all affected by how land is managed, food is grown, and nature is protected. Different experiences and perspectives may bring us to care about health and the environment and the devastating adverse effects of pesticides and toxic substances. However, ensuring a livable future requires us to cultivate a collective concern about daily decisions on the management of our personal and community spaces, the practices used to grow the food we buy, and the care that we as a society give to complex and fragile interrelationships that sustain the natural world on which we depend.Â
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source: BMC Public HealthÂ
