On May 30, 2023, the U.S. Environmental Protection Agency (EPA) announced it has taken additional steps in addressing concerns that per- and polyfluoroalkyl substances (PFAS) have been found in pesticide products. As part of its ongoing efforts, EPA has completed its verification analysis of a study published in September 2022 in the Journal of Hazardous Materials entitled “Targeted analysis and Total Oxidizable Precursor assay of several insecticides for PFAS.” This study reported the presence of perfluorooctanesulfonate (PFOS) in six of ten pesticide products tested. EPA released a summary of the laboratory analysis of the same ten pesticide products reported to contain PFAS residues. EPA states it did not find any PFAS in the tested pesticide products, differing from the results of the published study in the Journal of Hazardous Materials. In addition to the summary of its findings, EPA also is releasing its newly developed and validated analytical methodology used in the testing process. In its press release, EPA states it is “confident in the results of this newly released method, which is specifically targeted to detect the presence of PFAS in pesticide products formulated with surfactants.”

EPA evaluated the ten pesticide products included in this study using two different test methods to detect PFAS. The first method was developed by EPA’s Analytical Chemistry Branch (ACB) to measure specifically PFAS in pesticide samples containing surfactants and non-volatile oils, and the second method was used in the study published in the Journal of Hazardous Materials. EPA obtained samples of the specific pesticide products from the study author and purchased additional products with the same EPA registration numbers on the open market to conduct analyses.

EPA tested all samples using both methods and did not detect the presence of PFOS, nor any of 28 additional PFAS for which it screened, above the lowest level that the lab instruments can detect (0.2 parts per billion) in any of the pesticide products using either method of detection. According to EPA, the equipment and methodology used would have shown PFAS detections if present in those pesticide products, given that the level of detection (LOD) is 2,500 times more sensitive than the LOD reported by the equipment used by the study author. EPA requested additional information, including raw data from the study author, but did not receive any beyond the published results. EPA’s study report contains additional scientific details regarding how the two methods differ and the significance of using EPA’s new method when testing these specific formulations. EPA states one of the most important differences between the two methods is that EPA’s method ensures accurate measuring of PFAS by eliminating interference from the oils and surfactants present in these formulations that can result in false positive detections.

EPA’s testing and verification analysis is one of several steps EPA has taken since learning about potential PFAS contamination in a small number of mosquitocide products in September 2020. Other developments include (1) releasing data in March 2021 that preliminarily determined that PFAS in those specific products was most likely formed from a chemical reaction during the container fluorination process that then leached into the pesticide product; (2) releasing another study in September 2022 testing the leaching potential of PFAS over a specific time into test solutions packaged in different brands of high-density polyethylene (HDPE) fluorinated containers; and (3) notifying manufacturers (including importers), processors, distributors, users, and those that dispose of fluorinated HDPE containers and similar plastics that the presence of PFAS formed as a byproduct in these containers may be a violation of the Toxic Substances Control Act (TSCA). Following that notification, the Department of Justice, on behalf of EPA, filed a complaint against Inhance, the company that manufactured the plastic mosquitocide containers in which PFAS was found, for its failure to comply with TSCA’s notice, review, and determination requirements prior to manufacture.

According to EPA, its PFAS Strategic Roadmap renewed EPA’s commitment to using sound science and investing in research to stop proactively PFAS chemicals from entering the environment. EPA notes its latest action is an important step in its “ongoing efforts to better understand and manage, when necessary, pesticide formulations that contain PFAS to ensure enduring and protective solutions.”

Commentary

Considering the immediate and significant actions taken by EPA following the study report published in the Journal of Hazardous Materials, it is very interesting that EPA was not able to detect the presence of PFOS or 28 other PFAS substances under the same test method used in that published report and a second method developed by EPA. In the report’s conclusion, EPA states:

Although the SW846 Test Method 8327 is applicable for analyzing PFAS in samples that have been previously prepared using solvent dilution or extraction, due to the complex nature of pesticide products, preparation by solvent dilution is not an appropriate method. A more robust preparation method is necessary. Furthermore, since low amounts of PFAS are readily observed in the environment, incorrectly interpreted background data could be multiplied by a large dilution factor (if dilution was used as sample preparation), resulting in reporting of an overexaggerated concentration of a background PFAS or a false-positive identification. These large dilution factors utilized [in the study published in September 2022 in the Journal of Hazardous Materials] could have contributed to the high results obtained in that study.

Information regarding EPA’s new method may assist others involved in future PFAS detection testing. The different results and discussion by EPA illustrate some of the difficult issues surrounding the PFAS issue. PFAS itself is a bucket term that does not clearly have a defined set of members. Estimates range widely, from many hundreds to over 1,500 chemicals, depending on the definition used. The current torrent of public attention to the issue of PFAS has helped focus the time and attention of EPA and other regulatory bodies to address public concerns. These concerns center on questions of safety and, unfortunately, do not always recognize that sampling results are dependent on accurate chemical identity definitions and appropriate laboratory methods. Media coverage of the issue adds to the difficulty of these issues when attempting to explain study results in straightforward terms instead of presenting a more accurate explanation that reflects the underlying complexity regarding the definitions and methods used.