08
Apr
U.S. Geological Survey Finds PFAS Pesticides In California Streams
(Beyond Pesticides, April 8, 2026) Researchers at the U.S. Geological Survey (USGS) assessed pesticide and PFAS (per- and poly-fluoroalkyl substances) contamination in ten agricultural streams in the San Joaquin and Sacramento Valleys (Central Valley) in 2024, detecting 60 pesticides, synergists, and associated transformation products, including 12 fluorinated pesticides (Dithiopyr, Trifluralin, Fluridone, Oxyfluorfen, Penoxsulam, Flubendiamide, Bifenthrin, Flonicam, Indoxacarb, Cyhalothrin, Fluopyram, and Penthiopyrad) that meet the Organisation for Economic Cooperation and Development (OECD) definition of qualifying as PFAS. It is alarming to learn that “the OECD fluorinated pesticides were generally detected more frequently and at higher concentrations†relative to the 48 other compounds.Â
Relatedly, research finds products containing three of the detected pesticides (Methoxyfenozide, Imidacloprid, and Piperonyl Butoxide) associated with various PFAS, and according to the authors, there are a handful of active ingredients, such as the insecticide Methoxyfenozide and the fungicide Azoxystrobin, detected in 100 percent of collected samples. Their entire findings were published in Environmental Science & Technology Letters in March 2026.
This research is critical to our understanding of the pervasiveness and ubiquity of multi-chemical pollution that impacts one of the most productive agricultural regions in the country. The regions encompassing these two valleys make up just one percent of total U.S. farmland, yet produce eight percent of total agricultural production by output, including 4 in 10 of the country’s fruits and nuts, according to USGS. Unfortunately, the chemical-intensive status quo has led to significant evidence of off-target pesticide drift into community members’ households and schoolyards, emphasizing the dangers of bioaccumulation from resulting acute and chronic exposure to local communities and ecosystems, not to mention the downstream effects of residues that are spread in the supply chain across the U.S. and the globe. In this context, organically managed systems, as defined by the Organic Foods Production Act, have created a blueprint for least- and non-toxic pest management systems that ban the spread of toxic inputs (synthetic pesticides, fertilizers, PFAS, biosolid sewage sludge, and antibiotics and animal growth hormones for livestock). Â
Methodology and ResultsÂ
“The objective of this study was to evaluate pesticide applications as a source of PFAS in streams draining agricultural regions in California: San Joaquin Valley and Sacramento Valley,†says the USGS researchers. They continue: “Sites across the San Joaquin Valley and Sacramento Valley were sampled for 183 pesticides and pesticide transformation products (TPs) and 57 individual PFAS.†Â
Ten sites were selected across the Central Valley, with water samples gathered in May and July 2024. The sites were chosen based on two criteria: “minimal nonagricultural influences†to otherwise explain the source(s) of contamination and substantial levels of the pesticide product Intrepid 2F (methoxyfenozide), citing previous research finding “the presence of perfluorobutanesulfonate (PFBS)†in the formulation. The most recent pesticide data is from peak applications in 2021, collected by the California Department of Pesticide Regulation (DPR), operating on the assumption “that 2022 pesticide use data (the most recent year available) are representative of the 2024 pesticide data.â€Â A range of agricultural products (alfalfa, rice, tomatoes, nuts, etc.) are grown on the sites, information that assisted in determining relevant pesticides to test for. Â
There was no rain to impact pesticide residue data gathered in this study across both valleys in the days leading up to water sample collection in July 2024, with San Joaquin Valley experiencing less than 2.5 centimeters of rainfall the day before water testing in May 2024; Sacramento Valley also faced no rainfall in the days leading up to the May 2024 sample gathering. Researchers used various techniques to isolate and determine individual compounds (pesticides, PFAS, etc.), involving liquid and gas chromatography-tandem mass spectrometry (LC-MS/MS and GC-MS/MS). Across the ten sites (creeks and streams), summary data were developed, including “total PFAS concentration, total pesticide concentration, total OECD fluorinated pesticide concentration, PFAS counts, pesticide counts, and pesticide use (kg) normalized by watershed area (km2).â€Â
There are some additional notable findings from this study, including site-specific findings:Â
- Mustang Creek was expected to face higher concentration of OECD and non-OECD PFAS pesticides since the area faces the highest quantity of pesticides per acre and also boasts the most cropland compared to the ten other creeks. It is important to note that almond orchards are located near the site, which the authors tentatively attribute to higher concentrations of residues in May;Â
- PFOA and PFOS were detected in 60 percent and 35 percent of all water samples, respectively, with the remaining 11 PFAS having fewer than 3 detections each;Â
- Orestimba Creek had the highest PFAS concentration in May, with researchers attributing the PFBA (perfluorobutanoic acid related to PFAS) levels to some combination of fluorinated pesticide containers and pesticides sprayed on nut crops in the spring, the latter explanation plausible given the timing of the spring season application.Â
- Researchers highlight that PFAS contributions could also be explained through “the degradation of certain fluorinated pesticides and other organofluorine compounds to the ultrashort PFAS trifluoroacetate (TFA).” (See studies here and here for further details.) They continue: “Measurements and analyses of TFA and total organic fluorine (TOF) would likely yield a more complete assessment of pesticide applications as a PFAS source but were outside the scope of this study.”Â
- Only 57 of potentially thousands of PFAS chemicals were targeted due to the scope of the study. “Lasee et al. measured PFAS in insecticide formulations pre- and post-oxidation, with PFAS concentrations increasing post-oxidation,â€Â the authors state. They continue: “This suggests that pesticide formulations contain unmeasured PFAS that could oxidize to PFCAs and PFSAs.â€Â
The following pesticide-related compounds were detected at least once across the samples:Â Â
- Insecticides: Methoxyfenozide, Chlorantraniliprole, Clothianidin, Imidacloprid, Thiamethoxam, Carbaryl, Etoxazole, Flubendiamide, Acetamiprid, Bifenthrin, Cyantraniliprole, Flonicamid, Flupyradifurone, Cyhalothrin, Diazinon, Indoxacarb, Tebufenozide, and Thiamethoxam degradate;Â
- Herbicides: Diuron, DCPMU [Diuron metabolite], Metolachlor, 3,4-Dichloroaniline [building block for synthesis of herbicide active ingredients], Pendimethalin, Hexazinone, Atrazine Desiopropyl [transformation product], Clomazone, Bentazon, DCPU [Diuron metabolite], Dithiopyr, Simazine, Indaziflam, Trifluralin, Atrazine Desethyl [transformation product], Fluridone, Thiobencarb, Oxyfluorfen, Penoxsulam, Propanil,  Atrazine, Benziobicylon, and Propyzamide;
- Fungicides: Azoxystrobin, Propiconazole, Tebuconazole, Carbendazim, Fluopyram, Fluxapyroxad, Boscalid, Metconazole, Myclobutanil, Penthiopyrad, Pydiflumetofen, Difenoconazole, Metalaxyl, Pyrimethanil, Cyprodinil, Flutriafol, Pyraclostrobin, and Tebuconazole t-Butylhydroxy; and,
- The pesticide synergist piperonyl butoxide.Â
Previous CoverageÂ
For decades, Beyond Pesticides has continuously tracked the emergence of peer-reviewed science, research efforts, and policy and regulatory updates to inform the public, advocates, and decision makers on the dangers of synthetic agrichemicals and the transition to alternative pest management systems, including organic standards.Â
In the United States context, there is significant research continuing from data gathered in the Agricultural Health Study (AHS), a National Cancer Institute (NCI) and National Institute of Environmental Health Sciences (NIEHS) prospective study of cancer and other health outcomes in a cohort of licensed pesticide applicators and their spouses from Iowa and North Carolina. Between 1993 and 1997, with follow-up between 1999 and 2021, AHS tracks occupational and nonoccupational exposure and subsequent health effects from pesticide exposure. A recent study, published in Environmental Advances in partnership with Yale University associate professor of epidemiology Nicole Deziel, PhD, MHS, reexamines a quantitative analysis on nontarget, “active-ingredient-specific†exposure to pesticides from multiple pathways—applying new criteria to AHS spousal exposure to the insecticide chlorpyrifos and the herbicide atrazine. The three pesticide exposure pathways include take-home, agricultural drift, and residential use. (See Daily News here.) In another study focused on birth outcomes in Arizona (Journal of Exposure Science & Environmental Epidemiology), researchers find that preconception and prenatal exposure to certain carbamates, organophosphates, and pyrethroids increases the risk of lower Apgar scores, a metric used to assess neonatal health at one minute and ï¬ve minutes after birth. The results reveal that exposure to “several pesticide active ingredients at any point during preconception and/or pregnancy were associated with increased odds of low Apgar scores: the carbamates carbaryl and formetanate hydrochloride; the organophosphates diazinon and tribufos; and the pyrethroid cypermethrin.â€Â (See Daily News here.) Â
Additionally, the data in the annual U.S. Department of Agriculture (USDA) pesticide residue report, released earlier this year, continues to show a pattern of pesticide residues in the majority of food tested by USDA. In terms of the 76 samples that exceeded tolerances, those samples include one sample of avocados, 22 samples of fresh blackberries, eight samples of cherry tomatoes, five samples of cucumbers, three samples of fresh sweet corn, and 37 samples of tomatillos. For the avocado sample it was deltamethrin; for the fresh blackberries it was nine samples with acephate, six samples with cyhalothrin, and eight samples with cypermethrin; for cherry tomatoes it was two samples with acephate, one sample with captan, two samples with flonicamid, and four samples with Tetrahydrophthalimide (THPI); for the cucumbers it was one sample with cyazofamid, two samples with etoxazole, one sample with methomyl, and one sample with myclobutanil; for sweet corn it was two samples with Deltamethrin and one sample with permethrin; for tomatillos it was 36 samples of acephate that exceed tolerance thresholds. (See Daily News here.)Â
There is also significant research outside the U.S. context that demonstrates the pervasiveness of pesticide pollution and associated impacts on our bodies and planet. Researchers at the University of Caxias do Sul (Brazil) identify 29 peer-reviewed scientific studies with statistically significant findings that tie pesticide use to cancer diagnoses. The literature review is published in Saúde Debate. This collection of clinical trials, as well as epidemiologic, case-control, and experimental studies—from the United States, Brazil, India, France, Egypt, Colombia, Ecuador, Mexico, Italy, and Spain—add to the hundreds of peer-reviewed independent analyses connecting synthetic chemical dependency in food production and land management with mounting public health concerns. (See Daily News here.) A cohort of over 300 citizen scientists gathered data for a study published last year in Science of The Total Environment reporting widespread pesticide contamination collected from beehive monitoring across the European Union (EU). Among many concerning findings, the researchers concluded that, “There was no sample site where there was no pesticide occurrence over the complete sampling period.†(See Daily News here.)Â
Call to ActionÂ
Beyond Pesticides recommends choosing certified organic produce whenever possible—since pesticides cited in this study and virtually all synthetic pesticides are not allowed in organic food production. Through the Eating with a Conscience database, you can select from over 90 different common produce and veggies you regularly consume and learn about the organic difference from their conventional, chemical-intensive counterparts.Â
Additionally, you can sign up for Action of the Week and Weekly News Update to stay notified on ways you can take action to expand public investments and programs that expand organic land management, in agricultural contexts and on public green spaces, parks, and playing fields, to move beyond a reliance on synthetic materials. See ManageSafeTM for addressing pest prevention and management for land and buildings.Â
All unattributed positions and opinions in this piece are those of Beyond Pesticides.Â
