The Environmental Working Group's analysis found PFAS associated with pesticides in about half of California's surface-water samples and in roughly 45%–55% of sediment samples. Testing has been limited, so the true scope of contamination could be larger. A separate study estimates California farms applied about 2.5 million pounds of PFAS to crops annually from 2018–2023. PFAS are persistent "forever chemicals" linked to immune, liver and reproductive harms, and contamination can spread beyond farm fields into nearby communities and ecosystems.
Report: PFAS From Pesticides Found in Roughly Half of California's Waterways
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California's rivers, streams and sediments are showing widespread traces of per- and polyfluoroalkyl substances (PFAS) linked to pesticide use, a new Environmental Working Group (EWG) analysis warns. These persistent "forever chemicals" resist natural breakdown and can accumulate in soils, water and living tissues.
Key Findings
EWG's review of state and federal records found PFAS in about 50% of surface-water samples and in roughly 45%–55% of sediment samples across the state. While testing to date has been limited, the available data point to a potentially broad contamination problem.
Scope and Caveats
The report's authors stress that monitoring remains incomplete. Limited sampling and uneven geographic coverage mean the true prevalence of PFAS in California's waterways could be higher than current figures indicate. EWG co-author Varun Subramaniam told The Guardian the results are "alarming but not surprising." The group also highlights analyses suggesting many pesticide products contain PFAS-related chemistries.
Agricultural Sources
A separate study cited by EWG estimated California farms applied about 2.5 million pounds of PFAS to crops annually from 2018 through 2023, with highest applications concentrated in intensive agricultural regions. Because pesticides can be transported by runoff and wind, contamination originating on farms may reach nearby communities, wildlife habitats and other agricultural areas.
Health and Environmental Concerns
PFAS have been linked to a range of health issues, including altered immune and liver function, increased cancer risk, and pregnancy complications. Their extreme persistence means contamination identified today can continue to affect people and ecosystems for decades or longer — which is why researchers note that "PFAS never fully break down in the environment."
"These findings suggest pesticides could also be exposing millions of Californians to PFAS through water and soil. What's worse, exposure may persist for generations," EWG researchers wrote.
What Comes Next
Researchers and advocates say expanded, systematic testing is urgent to understand the full scale of contamination and to guide responses. Possible next steps include broader monitoring, targeted cleanup of hotspots, and regulatory review of pesticide products and PFAS use. For communities near intensive farming, the findings underscore the importance of water testing and public-health outreach.
Bottom line: Current evidence suggests PFAS linked to pesticide use are widespread in California's water and sediment, testing remains incomplete, and the potential public-health and ecological consequences warrant faster, more comprehensive action.
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