Despite years of work in environmental cleanup, PFASs remain a serious problem. PFASs are chemicals commonly used in fire-fighting foams, but also in manufacturing to make products more stain-resistant, waterproof and/or nonstick. PFASs are harmful to humans and particularly persistent in the environment due to the strong carbon-fluorine bonds.
PFASs are usually classified into two major groups; perﬂuorinated sulphonic acids (PFSAs) and perﬂuorinated carboxylic acids (PFCAs). Perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) are the two perfluoroalkyl (PFAAs) that have received the most attention due to their bioaccumulation potential, persistence, toxicity, and ubiquitous presence in the environment. PFOS was shortlisted as a Persistent Organic Pollutant (POP) by the Stockholm on Persistent Organic Pollutants (POPs) in 2009, while PFOA was anticipated to be a likely carcinogen by the United States Environmental Protection Agency (USEPA). In 2009, the USEPA established provisional health advisory (PHA) levels drinking water for PFOA and PFOS at 0.4 and 0.2 µg/L, respectively (USEPA, 2009). In May 2016, USEPA released a lifetime health advisory level for combined concentrations of PFOA and PFOS of 0.07 μg/L (parts per trillion) (USEPA, 2016a). Table 1 shows the most common PFASs, their molecular weight, and common acronyms.
|PFASs||Acronyms||Molecular Weight (g/mol)||Carbon Chain Length(n)||Formula|
Approximately 100,000 tons of PFASs are estimated to be present in the groundwater and drinking water across the country. None of the conventional and advanced treatments available today can degrade both PFOA and PFOS. These compounds can thus only be physically removed from water via filtration or adsorption, which are prohibitively expensive.