Biddle Air National Guard Base (formerly Horsham Air Guard Station)

Biddle Air National Guard Base, known as Horsham Air Guard Station from 2011 to 2021, is a Pennsylvania Air National Guard installation in Horsham Township, Montgomery County, Pennsylvania. The site began as a private airfield (Pitcairn Field) in 1928 and was commissioned as Naval Air Station Willow Grove in 1943, later operating as a Naval Air Station Joint Reserve Base. After the Navy departed in 2011, the property was transferred to the Pennsylvania Air National Guard and renamed Horsham Air Guard Station, and in 2021 it was renamed in honor of Charles Biddle. Today the installation hosts the 111th Attack Wing, which operates MQ-9 Reaper remotely piloted aircraft. It occupies part of the former Willow Grove naval air complex, where decades of flight and firefighting operations took place.

Like many installations where firefighting foam was used over long periods, the site has been the subject of concerns about potential exposure to persistent chemicals found in soil, groundwater, and nearby drinking water. The contaminants documented here are described below, with how each has been associated with possible health effects in the scientific literature.

1. AFFF: AFFF (aqueous film forming foam) is a fire suppressant historically used to extinguish fuel fires during training. At this base and the adjacent former naval air station, repeated use of AFFF has been identified as the suspected source of chemical contamination in groundwater. The foam contains the per- and polyfluoroalkyl compounds discussed below, which have raised concerns about potential long term exposure.
2. PFAS: PFAS are a large group of synthetic per- and polyfluoroalkyl substances valued for resisting heat, oil, and water, which also makes them persistent in the environment. At Horsham, PFAS associated with firefighting foam were detected in on-base wells, with combined concentrations reported as high as roughly 86,000 parts per trillion in testing around 2017. PFAS exposure has been associated in some studies with a range of potential health effects, which continue to be studied.
3. PFOS: PFOS (perfluorooctane sulfonate) is a specific PFAS compound that was a common ingredient in older firefighting foams. Combined PFOS and PFOA levels in many on-base wells at Horsham exceeded federal advisory thresholds, and the compound was among those detected in nearby public water supplies. PFOS has been associated in research with concerns about possible effects on cholesterol, the immune system, and other outcomes.
4. PFOA: PFOA (perfluorooctanoic acid) is another long-lasting PFAS compound linked to legacy firefighting foam. At this installation, PFOA was measured together with PFOS at levels well above the combined health advisory level in groundwater and in some surrounding wells. Research has associated PFOA exposure with a number of potential health effects, though findings vary across studies.

This installation is not itself listed on the National Priorities List, although the adjacent former Naval Air Station Joint Reserve Base Willow Grove is a Superfund site addressed under a federal facilities agreement among the EPA, the Pennsylvania Department of Environmental Protection, and the Navy. The Department lists Horsham Air Guard Station among the state's PFAS affected military sites, and cleanup is ongoing. The Air Force has funded treatment systems on nearby public water supplies and, under a state discharge permit issued in 2021, applies a combined PFOA and PFOS limit of 70 parts per trillion to water leaving the site.

Veterans, civilian employees, and family members who lived or worked at this base may wish to follow developments as monitoring and remediation continue. Anyone with questions about possible exposure is encouraged to stay informed through official updates and to speak with the U.S. Department of Veterans Affairs about health resources and benefits for which they may be eligible.