PFASs, such as PFOA and PFOS, have been used to manufacture a variety of industrial, commerical and military products, including (through 2001) PFOS-based fluorochemical surfactants (FCSs) used in AFFF. AFFF is used to extinguish flammable liquid (e.g., hydrocarbon) fires. Military Specification MIL-F-24385F mandates the use of FCSs in AFFF to meet performance requirements. Additional ingredients include organic solvents (i.e., glycol ether), foam stabilizers, and corrosion inhibitors. Over the past several years, manufacturers of FCSs have shifted to a telomerization process to produce FCSs for use in AFFF. While telomer-based FSCs do not contain or break down into PFOS, they may contain trace levels of perfluorocarboxylic acids (e.g., PFOA) as an impurity.
Environmental releases of AFFF occur from tank and supply line leaks, use of aircraft hangar fire suppression systems, and from firefighting training activities. Site investigations under the Defense Environmental Restoration Program (DERP) have not typically included analysis for PFASs given their emerging status. However, approximately 600 DERP sites are categorized as Fire/Crash/Training areas and thus have the potential for PFASs contamination due to historical use of AFFF.
PFOA and PFOS have attracted increased regulatory scrutiny because of their resistance to degradation, ability to bioaccumulate, and growing evidence of toxicity in animal studies. The U.S. Environmental Protection Agency (EPA) published Provisional Health Advisory values of 0.4 μg/L for PFOA and 0.2 μg/L for PFOS in drinking water. Additionally, the Agency for Toxic Substances and Disease Registry released a draft toxicological profile on perfluoroalkyls for public comment. Several state regulatory agencies have moved to establish action levels and guidelines for PFOA and PFOS. Minnesota established a health risk level of 0.3 μg/L in drinking water for PFOA and PFOS. New Jersey established a drinking water guidance value of 0.04 μg/L for PFOA. These levels are several orders of magnitude lower than concentrations of PFOA and PFOS observed in groundwater at historical fire training areas. EPA released draft documents on the health effects for PFOA and PFOS for public comment to better support future regulatory evaluations and decisions.
Due to their chemical structure, PFASs are very stable in the environment and are resistant to biodegradation, photo-oxidation, direct photolysis, and hydrolysis. While PFASs have been found to negatively affect autotrophic and heterotrophic food webs, additional data is needed to improve the understanding of their ecotoxicity. In addition, determining the toxicity of other PFASs in comparison to PFOS and PFOA will provide a more comprehensive understanding of the risk drivers