[co-author: Edward Mahaffey]
Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) are found in firefighting foam used by the military since the 1970’s for training exercises and to extinguish liquid and gas fires. These compounds are part of a larger class of toxic chlorinated chemicals called per- and polyfluoroalkyl substances (PFAS). Similarly, airports and municipal fire departments have used the aqueous film forming foam (AFFF) for decades to extinguish fires caused by flammable liquids.
Firefighting foams are divided mainly into two classes. Class A foams are used to fight wildfires and structural fires. Class B foams are used to extinguish fires caused by flammable liquids. While not all Class B fire extinguishing agents contain PFAS, all AFFF does, and AFFF has special characteristics that make it difficult to find adequate replacements. When mixed with water, AFFF produces an aqueous spreading film that extinguishes burning hydrocarbon fuel and prevents reignition by cutting off oxygen from the fuel source.
PFAS compounds are believed to cause multiple health problems. Studies link the chemicals to immune system and endocrine disorders, thyroid problems and some cancers, at fairly low doses (measured in parts per trillion). In 2016, EPA issued a lifetime health advisory for PFOS and PFOA of 70 parts per trillion (ppt) in drinking water. Also, in 2018, ATSDR reported that exposure to lower levels of PFOS and PFOA could cause increased cancer risks and other health issues in humans. In late 2019, EPA issued a separate health advisory setting 70 ppt as the recommended cleanup level for these PFAS compounds in groundwater.
PFAS chemicals, including those in AFFF, are labeled “forever chemicals” because they are ubiquitous and extremely difficult to remove from environmental media. It is believed that most people have PFAS compounds in their blood serum – from drinking water and a variety of other consumer products – although there is a lack of consensus at what threshold PFAS may trigger health risks.
In the early aughts, manufacturers started phasing out AFFF containing PFOS, one of the most common PFAS compounds. However, AFFF formulations containing other long-chain PFAS compounds, including trace amounts of PFOA, continued to be made in the United States until at least 2016. AFFF has a long shelf life, and the military stockpiled the agent for continued use, although the Department of Defense officially ended the use of AFFF in training exercises in January 2016, and Congress, in the National Defense Authorization Act of 2020, directed DOD to develop an effective PFAS-free Class B firefighting foam to replace AFFF no later than October 2024. In the meantime, several state legislatures have banned the use of AFFF.
The ubiquitous use of AFFF for many years by the military has contaminated potable water sources on and near numerous military bases across the United…