In May 2023, the United States Environmental Protection Agency (EPA) announced the results of its analysis of ten different pesticide products sampled for the presence of per- and polyfluoroalkyl substances (PFAS). EPA's sampling efforts were prompted by a highly publicized September 2022 third-party study that reported the presence of PFAS (in particular, perfluorooctanesulfonate (PFOS)) in six out of ten pesticide products sampled. The September 2022 study caused alarm as to the potential for unknown PFAS content or cross-contamination of certain pesticide products. However, EPA's more recent sampling of ten pesticide products, using a new and purportedly more accurate sampling method, casts doubt on the prior sampling results since EPA did not detect PFAS in any of the ten pesticide products it sampled. EPA emphasized in its May 2023 announcement that it is confident in the results of its newer sampling method, which is specifically targeted to analyze for PFAS in pesticide products formulated with surfactants and non-volatile oils.
EPA obtained samples of the ten pesticide products from the third-party study author and from purchases of the same products on the open market. EPA evaluated the ten pesticide products using both EPA's new method (the ACB Method) and the method used in the third-party's earlier study (the Lasee Method). EPA did not detect any of the 29 additional PFAS for which EPA screened the pesticide products for (including PFOS), above the lab instrument's detection limit of 0.2 parts per billion (ppb). Notably, EPA's detection limit is 2,500 times more sensitive than the limit in the earlier third-party study. EPA requested additional information and raw data from the study author but did not receive anything other than the published results.
The variance between the results of the 2022 third-party study and EPA's verification analysis demonstrates the potential pitfalls in preparing samples using a solvent dilution. If a solvent dilution is used in sample preparation, data showing low amounts of PFAS could be multiplied by a large dilution factor, resulting in a "false-positive" identification of PFAS. The large dilution factor was used in the 2022 third-party study, which may have contributed to the positive identification of PFAS in the pesticide products.
EPA's ACB Method offers another avenue to perform PFAS detection testing. The ACB Method is intended to eliminate the use of solvent dilution in the sample preparation process and reduce the potential for a "false-positive" detection of PFAS in pesticide products.
Helpful Links
- EPA's May 18, 2023 Memorandum on Verification Analysis for PFAS in Pesticide Products, click here.
- Details on the ACB Method, click here.
- "Targeted Analysis and Total Oxidizable Precursor assay of several insecticides for PFAS" in the Journal of Hazardous Materials, click here.
- Questions & Answers on PFAS in Pesticides, click here.
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