Aqueous film-forming foams (AFFFs)
AFFFs have been used at military bases, airports, and firefighting training sites to suppress flammable liquid fires, and several PFAS compounds have been ingredients in these products. Uncontained AFFF runoff has migrated through soil to contaminate nearby aquifers and surface waters at a number of sites in the United States.
Facilities that produced PFAS products or used PFAS in manufacturing processes have released the chemicals through wastewaters, solid waste, and air emissions.
At several historic landfill sites, PFAS-contaminated waste has contributed to PFAS levels in leachate—liquid that has passed through waste disposed in an active landfill and accumulates dissolved and suspended matter from it—that subsequently contaminated natural waters. Today, untreated landfill leachate may pose a contamination risk.