O'Hare Air Reserve Station

O'Hare Air Reserve Station was a roughly 350-acre Air Force Reserve installation located at Chicago O'Hare International Airport on the city's Northwest Side in Illinois. The reserve station operated from about 1970 until 1999 and at various times hosted units including the 928th Airlift Wing and the 126th Air Refueling Wing, supporting airlift and aerial refueling missions. The 1993 Base Realignment and Closure (BRAC) round recommended the station's closure, and operations were relocated to Scott Air Force Base in southern Illinois, with the reserve presence at O'Hare ending in the late 1990s. Like many flying installations of its era, the station maintained fire response capabilities to handle the intense fuel fires associated with military and commercial aircraft. Although the military facility has closed, the surrounding airport remains one of the busiest in the country.

Years after the station closed, Air Force environmental investigators examined the former property as part of a wider review of firefighting foam use at current and former installations. Their work identified contamination concerns tied to past firefighting and training activities, and several locations have been flagged for further study.

1. PFAS: PFAS (per- and polyfluoroalkyl substances) are a large family of synthetic "forever chemicals" valued for their resistance to heat, water, and grease. At the former O'Hare station, PFAS are associated primarily with the long-term use of firefighting foam, and the Air Force reported PFAS contamination in groundwater beneath the airport. One published analysis associated with the site reported PFHxA, a shorter-chain PFAS, at levels reaching roughly 14,400 parts per trillion. PFAS exposure has been associated in research with effects on cholesterol, the immune system, and certain cancers, though findings vary by compound and exposure.
2. AFFF: AFFF (aqueous film-forming foam) is a PFAS-containing firefighting foam used to suppress jet-fuel fires. Air Force investigators documented that the station's fire facilities stored tanks holding thousands of gallons of foam and noted multiple foam spills at different locations during the 1990s. Concerns about potential exposure relate to the PFAS compounds that AFFF can release into soil and groundwater.
3. PFOS: PFOS (perfluorooctane sulfonate) was a primary ingredient in legacy AFFF formulations historically used at military airfields. Because of its persistence, PFOS is among the compounds typically evaluated at former foam-use sites such as this one. Studies have associated PFOS exposure with potential health effects, and it is frequently measured in environmental sampling.
4. PFOA: PFOA (perfluorooctanoic acid) is another long-chain PFAS commonly assessed alongside PFOS at sites where firefighting foam was used. It has been associated in some studies with concerns about potential exposure, which is why it is included in PFAS testing at sites like O'Hare.

The former O'Hare Air Reserve Station is not listed on the National Priorities List (Superfund). Investigation and cleanup are being addressed through Department of Defense and Air Force programs as part of a nationwide PFAS response. A 2020 Air Force report identified eleven locations at the former training site that warranted further investigation, a city contractor removed about 200 tons of PFAS-contaminated soil for off-site disposal, and additional testing has been planned. An initial survey reported that no drinking-water wells within about a mile were immediately threatened, in part because the Chicago area draws its drinking water from Lake Michigan.

Veterans, civilian workers, and family members who spent time at or near the former O'Hare Air Reserve Station may wish to stay informed as investigation and testing continue. Those with questions about possible exposure are encouraged to keep records of their service and to speak with the U.S. Department of Veterans Affairs about health resources, screening options, and any benefits for which they may qualify.