On Feb. 26, 2019, the U.S. Environmental Protection Agency (EPA) published its latest efforts to evaluate the toxicity of per- and polyfluorinated alkyl substances (PFAS) in accordance with its previously announced PFAS Action Plan. As previously discussed in blog posts here, here, here, here and here, PFAS are a category of man-made chemicals that have been widely used to make products because of their stain-resistant, waterproof and/or nonstick properties.

The topic of PFAS toxicity has garnered much interest from regulators and the public. EPA previously established health advisories for two PFAS compounds, perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS). Based on data collected from EPA's third unregulated contaminant monitoring rule (UCMR 3) completed in 2016, approximately six million residents of the United States served by 66 public water systems had drinking water with concentrations of PFOA or PFOS, separately or combined, above the EPA's Lifetime Health Advisory.

Since issuing its health advisory for two compounds (PFOA and PFOS), EPA published its draft toxicity assessment for GenX chemicals and perfluorobutane sulfonic acid (PFBS), additional members of the larger group of PFAS compounds. GenX is a trade name for a technology that is used to make high-performance fluoropolymers (e.g., some non-stick coatings) without the use of PFOA. PFBS is a replacement chemical for PFOS, a chemical that was voluntarily phased out by its manufacturers.

In addition, the U.S. Department of Health and Human Services (HHS), Agency for Toxic Substances and Disease Registry (ATSDR) released its 852-page draft for public comment of its Toxicological Profile for Perfluoralkyls evaluating data concerning fourteen different PFAS compounds: Perfluorobutyric acid (PFBA), Perfluorohexanoic acid (PFHxA), Perfluoroheptanoic acid (PFHpA), Perfluorooctanoic acid (PFOA), Perfluorononanoic acid (PFNA), Perfluorodecanoic acid (PFDeA), Perfluoroundecanoic acid (PFUA), Perfluorobutane sulfonic acid (PFBuS), Perfluorohexane sulfonic acid (PFHxS), Perfluorooctane sulfonic acid (PFOS), Perfluorododecanoic acid (PFDoA), Perfluorooctane sulfonamide (PFOSA), 2-(N-Methyl-perfluorooctane sulfonamide) acetic acid (Me-PFOSA-AcOH), and 2-(N-Ethyl-perfluorooctane sulfonamide) acetic acid (Et-PFOSA-AcOH).

However, according to EPA, over 5,000 different chemicals have been identified in an EPA-compiled Master List of PFAS Substances. A major effort was undertaken by EPA researchers within the National Center for Computational Toxicology to curate and structure-annotate several public lists to come up with the Master List which encompasses PFAS of potential interest based on environmental occurrence (through literature reports and analytical detection) and manufacturing process data, as well as lists of PFAS chemicals procured for testing within EPA research programs. From this list of 5,061 compounds, EPA has selected 75 for its next round of evaluation out of 430 unique substances contained in its "PFAS screening library." The set of 75 samples consists of 74 unique substances plus perfluorohexanesulfonate procured from two different suppliers. Substances were selected based on a prioritization scheme that considered EPA Agency priorities, exposure/occurrence considerations, availability of animal or in vitro toxicity data and ability to procure samples. A summary of the "Prioritization Approach" for selecting PFAS substances for further investigation was recently published in Environmental Health Perspectives.

In summary, the goal is to develop a risk-based approach for conducting toxicity testing for PFAS substances which have not previously been subject to the extensive analysis used to develop the health advisories for PFOA and PFOS in an effort to address a growing concern where data remains limited. Only time will tell if the effort will produce results quick enough for the American public.