About half of California's waterways tested by regulators are contaminated with pesticides classified as "forever chemicals" (PFAS), according to a new analysis of state and federal records, highlighting the risks of widespread use of these substances that are only beginning to be recognized.
Pesticides are linked to a range of health problems, including cancer, and this study is the first to systematically test for hazardous substances in streams and rivers, including drinking water supplies.
More than half of the sediment samples also contained pesticides at some concentration, as they are increasingly used on agricultural crops in California and across the country.
This week, the results of an analysis of data from the California Department of Pesticide Regulation and the U.S. Geological Survey were released, just days before a proposal to potentially ban PFA pesticides failed to pass the state legislature. However, some provisions of the bill, including a moratorium on approving new pesticides, were adopted.
The findings are "alarming but not surprising," said Varun Subramaniam, one of the report's co-authors from the nonprofit Environmental Working Group (EWG).
«"It's concerning that we're finding these levels of the pesticide Pfas... but it was used at very high concentrations on agricultural products, so it's not surprising that it's ending up in streams and sediments," he said.
PFAs are a class of at least 16,000 compounds commonly used to make products water-, stain-, and grease-resistant. They have been linked to cancer, birth defects, decreased immunity, high cholesterol, kidney disease, and a host of other serious health problems. They are called "forever chemicals" because they can persist in the environment for thousands of years and are designed to be indestructible.
These chemicals are added as active ingredients to food pesticides to kill weeds or insects, or used as inert ingredients. An analysis of EPA data from 2023 found that at least 60% of the active ingredients in pesticides met the most common definition of PFAS (polyphenols containing toxic substances).
An analysis of government records last year found that California farms applied an average of 2.5 million pounds of PFA pesticides annually to cropland between 2018 and 2023. Recent regulatory inspections found pesticide residues on 371 TP3T of total produce. However, approximately 901 TP3T of peaches, plums, and nectarines contained PFA, and 801 TP3T of strawberries and grapes also did so.
Health officials had argued that pesticides were almost certainly contaminating nearby water sources, and a new analysis confirmed their theory. Regulators analyzed streams from only 10 counties and found the highest concentrations in agricultural areas, including Monterey and San Luis Obispo counties.
Previous studies have shown that the highest use of Pfa pesticides was recorded in Fresno and Kern counties, but water pollution data were not collected in these regions. According to Subramaniam, the results are "almost certainly an underestimate" due to the limited scope of the study.
At least 10 polyphenols have been detected in pesticides across the state. The pesticide bifenthrin, one of the most toxic and linked to cancer, was detected in all water bodies in San Luis Obispo, as well as in more than 80% samples in Stanislaus County, which includes Modesto and part of the Central Valley.
Assessing the health risk is difficult because pesticide regulations don't require companies to assess many of the health risks inherent to PFAs, such as immunotoxicity, reproductive harm, or hormonal disruption, in part because regulators lack adequate resources, Subramaniam said. Regulators also don't consider the cumulative effects of consuming PFA-contaminated water and then consuming products containing their residues.
«"These chemicals are allowed to be used in large part because we don't consider all the ways they can harm us," Subramaniam added.
Under pressure from the influential agricultural lobby, a proposal to completely ban PFA pesticides by 2035 failed, but the moratorium on new pesticides remained. The California Farm Bureau, opposing the bill, wrote that it was "an overly broad and unworkable approach that departs from science-based regulation." It argued that California farmers would be at an economic disadvantage, and the public health benefits would be negligible.
The legislation still includes a new requirement for pesticide packaging to carry warnings for farmers about the use of PFAs (polyphenols), which pose health and environmental risks. Susan Little, legislative affairs director at EWG California, stated that most farmers are unaware they are spraying PFAs on their crops.
The legislation also gives local authorities greater authority to restrict pesticide use and defines these pesticides as PFAS, which is consistent with most scientific definitions. Currently, the California Pesticide Agency uses a narrow definition of PFAS, which is popular with the industry in part because it excludes smaller compounds similar to those used in pesticides.
Supporters argue that this law is especially necessary given the Trump administration's rush to approve more PFA-listed pesticides. The California Pesticide Board also recently reapproved the PFA-listed insecticide sulfoxaflor, despite its approval having been repeatedly overturned by state and federal courts due to its high toxicity to honeybees and other pollinators.
Little said animal rights advocates were "disappointed" that the ban was not included in the final bill, but added that the bill, if approved by the state Senate, "will continue to address the issue of reducing PFA pesticide use in California.".