Jet fuel is made to burn. When airplanes crash, the reserve of the hydrocarbon liquid can produce a massive, violent fireball. Water, which doesn’t mix with the fuel, does little to extinguish these explosive fires, often just boiling off or sinking ineffectually under the fuel itself. So, about 50 years ago, the Minnesota-based chemical manufacturer 3M, in conjunction with the Navy, developed a product that would help extinguish such fires.
The sudsy liquid, dubbed “Aqueous Film-Forming Foam,” or AFFF, put out hydrocarbon fires more quickly and effectively than ever before by smothering them. Since it was developed, the military has been using huge quantities of the foam, which has been heralded for saving firefighters’ lives. Unfortunately, 3M’s miracle product also contained PFOS. And the other official formulation of the foam purchased by the Department of Defense contains “telomers,” compounds that can break down into PFOA and other PFCs. In addition to being linked to health problems, PFOA and PFOS stay in the human body for years and, unless they are removed, persist in the environment indefinitely.
The extent of contamination would no doubt be far less if the military had just used the foam to put out crash fires, which are fairly rare. Between 1979 and 2000, for instance, there were only four plane crashes near Willow Grove. But the foam is also used to teach soldiers to put out fires, and those training exercises are common. A typical exercise, which has been conducted by various branches of the military many thousands of times since the 1960s, involves flooding a fire pit with flammable liquids, lighting them on fire, and then putting out the flames with between 75 and 100 liters of firefighting foam. For decades, no one thought to construct barriers at these sites to contain the foam, which sank down through the earth into the water table.