California ended sales of most chlorpyrifos products in 2020 and later prohibited nearly all agricultural use in the state as of January 1, 2021. But that does not mean California residents have not been exposed to chlorpyrifos, a pesticide that studies have linked to Parkinson’s Disease.
Those living in California’s Central Valley, particularly the San Joaquin Valley, may face elevated risk years later, according to a UC Davis study. Researchers found that 7 of 31 adults and 1 in 11 children were exposed to detectable levels of pesticides simply by living, working, or attending school near agricultural areas that sprayed agrichemicals.
In this blog, we discuss some of the reasons why Central California residents, particularly those in areas where chlorpyrifos was heavily sprayed, may want to discuss potential risks with their healthcare provider. For those who were exposed to chlorpyrifos and later developed Parkinson’s, you may qualify for a lawsuit.
For more information, contact the chlorpyrifos lawyers at Wisner Baum for a free and confidential case evaluation.
How Central Valley Agriculture Shaped California's Chlorpyrifos Use
California’s Central Valley is one of the most prolific food-producing regions in the world, the heart of a state whose overall crop value of nearly $43 billion led all U.S. states in 2022. Before the California chlorpyrifos ban, chlorpyrifos was one of the most widely used pesticides on crops throughout the region. The state historically applied chlorpyrifos on over 60 crops across over 800,000 acres. An evaluation by the California Department of Food and Agriculture found that six commodities (alfalfa, almonds, citrus, cotton, grapes, and walnuts) accounted for 86% of statewide chlorpyrifos use in 2017.
Due to the heavy concentration of pesticides applied in the region, residents of five San Joaquin counties (Fresno, Kern, Tulare, San Joaquin, and Madera) are at the highest risk of exposure. According to the UC Davis Health study, 22% of adults and 10% of children who participated in the study were breathing detectable levels of pesticides tied to health concerns in prior research.
Which Crops Drove the Heaviest Chlorpyrifos Use
According to PAN (Pesticide Action & Agroecology Network), California used nearly one million pounds of chlorpyrifos in 2016. Around 73% of chlorpyrifos applications that year were used on just three crops:
These crops are heavily concentrated in the state’s Central Valley. Research shows that nearly 25% of chlorpyrifos was applied via aerial spraying, exposing large numbers of people in the area to the chemical.
Other high-volume crops, including citrus, walnuts, and grapes, also accounted for heavy use of chlorpyrifos. A 2017 Fact Sheet by Californians for Pesticide Reform, using 2010 state data, identified 305 schools attended by more than 150,000 children in five counties where chlorpyrifos was used nearby.
The Central Valley Counties Most Affected
Research shows that residents within five counties located inside California’s Central Valley were at the highest risk of exposure to chlorpyrifos due to concentrated application of the pesticide.
Central Valley counties most affected by chlorpyrifos use:
- Fresno: Chlorpyrifos was applied on alfalfa, almonds, cotton, grapes, oranges, walnuts, and other crops.
- Kern: The pesticide was frequently sprayed on citrus and other commodity crops.
- Madera: Chlorpyrifos was applied on almonds, grapes, pistachios, alfalfa, and other crops grown in the county.
- San Joaquin: The pesticide was used on several crops, including alfalfa, almonds, citrus, cotton, grapes, pistachios, and walnuts.
- Tulare: Pesticides, including chlorpyrifos, were used on alfalfa, oranges, walnuts, grapes, almonds, lemons, and other crops found in the area.
A 2026 UCLA Health study found that long-term chlorpyrifos exposure was associated with a 2.5-fold increased risk of developing Parkinson’s disease. As the UCLA study suggests, people who lived or worked near heavily treated fields may face an elevated risk of certain health conditions, including Parkinson’s disease. While residency or potential exposure does not automatically qualify a person to take legal action, it is important to be aware of the risk of exposure and to engage in regular health monitoring.
How Exposure Reached Residents Beyond Farmworkers
Individuals who resided, worked, or went to school in California’s Central Valley may have been exposed to neurotoxic chemicals, such as chlorpyrifos. Exposure was not limited to agricultural workers. People living, working, or going to school near farmland where the pesticide was applied may have been exposed through pesticide drift, contaminated air and water, household dust, and other pathways.
According to the California Department of Public Health’s April 2014 report on agricultural pesticide use near California’s schools, out of all pesticides analyzed, “chlorpyrifos was the eighth most common highly hazardous pesticide used within 1/4 mile of public schools in the 15 counties studied. Over 7,700 pounds of chlorpyrifos were applied in a single year within 1/4 mile of 438 schools, putting tens of thousands of students at risk.”
Communities That Faced Increased Exposure
Studies show that some communities in California’s Central Valley face an increased risk of exposure. Research published in 2020 found that chlorpyrifos use was disproportionately higher in Hispanic communities throughout the valley. According to the research, Hispanic children were 91% more likely than white children to attend schools in the highest quartile of nearby use of the pesticides studied.
Why the 2021 Ban Did Not Erase Decades of Exposure
While California ended virtually all agricultural use of chlorpyrifos, with limited exceptions for certain granular products, as of January 1, 2021, the ban could not undo years of exposure. Today, residents of California’s Central Valley may continue to experience exposure from legacy contamination.
Timeline of the chlorpyrifos ban in California:
- February 2020: Chlorpyrifos sales to growers ended in California. Residential use of the pesticide had been phased out by the end of 2001.
- December 2020: Use and possession of most chlorpyrifos products ended.
- January 2021: California declared chlorpyrifos-free, with limited exceptions for certain granular products.
A 2026 study found that despite this ban, chlorpyrifos was still found in 63% of personal air samples, 71% of indoor home samples, and 86% of the homes sampled. Residents may still face exposure from residual contamination in homes and soil from decades of heavy use, even though the pesticide is banned.
These findings suggest that, because chlorpyrifos breaks down slowly indoors, the ban has not eliminated detectable levels in homes; the study's authors estimate a roughly five-year half-life for the chemical in home environments.
Wisner Baum Represents Chlorpyrifos Plaintiffs Nationwide
Wisner Baum currently represents clients nationwide who were exposed to chlorpyrifos and later diagnosed with Parkinson’s disease or another qualifying condition. Qualifying for a lawsuit typically requires proving that chlorpyrifos exposure likely contributed to your Parkinson's diagnosis. This usually depends on individual factors including exposure history, medical records, and expert testimony.
Contact Wisner Baum today at (310) 207-3233 to schedule a free, confidential case evaluation. We can help explore whether you or your loved one may be eligible for a chlorpyrifos lawsuit and what steps you need to take to protect your rights.
