EPA lab contradicts previous study on PFAS in pesticide products


May. 30, 2023

The Environmental Protection Agency has issued a report reviewing a 2022 study on per- and polyfluoroalkyl substances detected in pesticide products. The report contradicts the findings of the 2022 study, using both the method of testing in the study as well as the agency’s own test procedures.

Regulatory background

  • Per- and polyfluoroalkyl substances (PFAS) are a wide class of synthetic organic chemicals used in many different industrial and commercial applications. PFAS break down extremely slowly in the environment due to the strength of the carbon-fluorine bonds within the molecule, leading to PFAS persisting in the environment. PFAS may enter the environment through many different environmental media, such as wastewater and industrial discharges from facilities that use or process PFAS, consumer products, or through the use of aqueous film-forming foams (AFFFs) for fire control.
  • The Environmental Protection Agency (EPA) has a variety of testing methods that it uses for determining PFAS concentrations in different media. The most prominent tests, Methods 533 and 537.1, determine the amount of PFAS in drinking water. Other test methods include Method 8327, which tests for 25 different PFAS in groundwater, surface water, and wastewater media, as well as Draft Method 1633, which tests for 40 PFAS in wastewater, surface water, groundwater, soil, biosolids, sediment, landfill leachate, and fish tissue.
  • In 2021, the EPA released a memorandum from the Analytical Chemical Branch (ACB) under the Office of Chemical Safety and Pollution Prevention (OCSPP) on methods for testing high-density polyethylene (HDPE) containers for PFAS concentrations. In addition, ACB released a method for testing for PFAS in oily matrices, such as pesticide products that are formulated in oil, petroleum distillates, or mineral oils, in September 2021.
  • In 2022, the Journal of Hazardous Materials Letters published Targeted analysis and Total Oxidizable Precursor assay of several insecticides for PFAS, which reviewed PFAS concentrations on 10 different insecticide formulations used on a United States Department of Agriculture crop research field. The study detected perfluorooctane sulfonic acid (PFOS) in six of the 10 formulations, with concentrations between 3.92 and 19.2 mg per kg (or parts per million). The study reviewed both PFAS concentrations as well as PFAS precursors in the insecticides and determined that the concentrations indicated a “previously unknown potential PFAS contamination source for rural and agricultural environments.”

EPA verification report

  • On May 30, 2023, ACB released its report on its attempts to verify the information found in the 2022 study. ACB acquired aliquots (samples) of the same ten pesticide products from the 2022 study authors in addition to four of the six pesticide products on the open market that the 2022 study determined contained PFOS. ACB utilized two methods for testing the samples, the first being the method utilized by the 2022 study, with the second being a newly-unveiled method for PFAS in pesticide formulations containing non-ionic surfactants and oil.
  • The major difference between the two methods is how the sample is prepared for testing. In the 2022 study method, the pesticide is diluted in a solvent and water solution and uses a single instrument for analysis of potential PFAS contamination within the solution. The ACB method utilizes a more involved extraction and cleaning procedure to isolate PFAS compounds within the matrix before analysis and reduces overall interference within the matrix. Both methods utilized SW-846 Test Method 8327 for analysis of the samples themselves.
  • The agency was not able to detect PFAS compounds above the instrument’s background levels of PFAS (10 parts per trillion, several orders of magnitude smaller than what was detected in the 2022 study). ACB did not detect the tested-for PFAS compounds in the samples obtained from the 2022 study authors, or the four pesticides purchased on the open market. In addition, ACB spiked two quality control samples with known amounts of PFAS (one and nine ppm) and recovered upwards of 40% of the PFAS in both samples utilizing multiple analytical instruments.
  • ACB’s own extraction method can reliably detect down to about .2 parts per billion (ppb), about 1000x lower than the dilution method utilized in the 2022 study. However, the agency still did not detect PFAS in the samples prepared using the ACB method, except for samples that were knowingly spiked with PFAS for quality control purposes.
  • Based on its results, ACB stated that it could not confirm the presence of PFOS as detected in the 2022 study, nor could it detect PFAS above method detection limits. ACB stated that although the SW-846 Test Method 8327 is applicable for analyzing PFAS in samples that have been previously prepared utilizing solvent dilution or extraction (how the 2022 study was conducted), the complex nature of pesticide products leaves the preparation ill-equipped for real world testing. In addition, ACB stated that more robust preparation methods are necessary for testing PFAS in pesticides, and that incorrectly interpreted background data in the 2022 study could have resulted in overexaggerated concentrations of PFAS or a false-positive identification.

Next steps

  • Although nothing actionable will come in the wake of this report in terms of regulations, the new method prepared by the EPA is helpful (even though it may not be validated for multi-lab use yet). In addition, ACB’s statement that traditional solvent dilution is not enough to effectively analyze PFAS in pesticides matrices indicates that although the agency plans to increase PFAS testing, especially in consumer products and pesticides, a “one-size-fits-all” approach may not work in many cases.

To contact the author of this analysis, please email Walker Livingston.
To contact the editor of this analysis, please email Patricia Iscaro.

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