AFFF exposure refers to human contact with aqueous film-forming foam, a firefighting foam that contains per- and polyfluoroalkyl substances (PFAS), often called “forever chemicals.” These synthetic compounds don’t break down in the environment or the human body, and they’ve been linked to several serious health problems including testicular cancer, kidney cancer, and disrupted infant development. AFFF has been widely used since the 1960s at military bases, airports, and fire training facilities, meaning exposure extends well beyond the firefighters who handled it directly.
What AFFF Contains
AFFF works by spreading a thin film over burning fuel, cutting off oxygen and smothering the fire. The chemicals that make this possible are PFAS, specifically fluorinated compounds that repel both oil and water. Older formulations manufactured before 2003, sold by 3M under the brand name “Lightwater,” contained long-chain (C8) compounds, primarily PFOS and PFOA. These are the most studied and most harmful variants.
Modern AFFF uses short-chain (C6) fluorotelomer-based compounds, which don’t break down into PFOS or other long-chain PFAS in the environment. However, the newer formulations can still contain trace amounts of PFOA as manufacturing byproducts, measured at parts-per-billion levels. Neither generation of foam is harmless, and both leave persistent contamination wherever they’re used.
How People Get Exposed
Exposure happens through three main routes: skin contact, inhalation, and ingestion. For firefighters, all three are common. PFAS chemicals used in AFFF can be absorbed directly through the skin during firefighting or training exercises. Aerosolized foam releases PFAS into the air, where it enters the lungs. Ingestion often happens indirectly through hand-to-mouth transfer from contaminated gear after a suppression event.
For the general public, the primary route is drinking water. When AFFF is sprayed during a fire or training drill, the chemicals soak into the ground and migrate into aquifers. Research from AFFF-impacted sites in Finland found that even a single fire suppression event can lead to long-term PFAS discharges into surrounding soil and groundwater. These chemicals don’t degrade, so contamination from a training exercise decades ago can still be leaching into wells and municipal water sources today. The most significant risks to nearby communities come from groundwater use and consuming fish from contaminated waterways.
Who Faces the Greatest Risk
Firefighters carry the highest burden. Those with a history of using AFFF have elevated blood levels of PFOS and PFHxS, a related compound. A study of Australian and Canadian firefighters found the highest individual concentrations of PFOS and PFHxS were roughly ten times greater than levels seen in the general population. Military firefighters face compounded risk because AFFF was used extensively at Department of Defense installations for decades, both in actual emergencies and routine training.
Communities near military bases, airports, and fire training sites are the next most affected group. Research on U.S. Air Force servicemen found that elevated blood levels of certain PFAS were associated with serving as a firefighter or simply being stationed at a base with high PFAS levels in the water supply. You don’t need to have touched the foam directly. Living downstream from a contaminated site and drinking the water is enough.
Health Effects Linked to Exposure
The health concerns fall into two broad categories: cancer and developmental disruption.
On the cancer side, elevated blood levels of PFOS have been specifically associated with higher risk of testicular cancer in a study of U.S. Air Force servicemen conducted by the National Cancer Institute. Kidney cancer has also been a persistent concern in PFAS research, though PFOS showed the strongest individual link to testicular cancer in that study. Other PFAS compounds tested did not show the same association, suggesting the specific type of chemical matters.
For pregnant women, PFAS exposure raises a different set of concerns. Higher maternal concentrations of PFOA during pregnancy have been consistently linked to lower birth weight. Research from the Healthy Start Study found the effects are sex-specific: female infants born to mothers with higher PFOS levels had lower weight-for-age scores, while male infants exposed to higher PFOA levels showed increased body fat in early infancy. Some PFAS compounds were associated with more than double the odds of rapid weight gain in the first months of life, a pattern that may set the stage for higher weight and body fat in early childhood. The picture is complex, with lower weight at birth followed by accelerated growth afterward, but the consistent finding is that these chemicals interfere with normal fetal and infant development.
Testing Your Exposure Level
Blood tests can measure PFAS concentrations, but they aren’t widely available through standard healthcare channels. The CDC and the Agency for Toxic Substances and Disease Registry developed a PFAS Blood Estimation Tool as an alternative. This web-based calculator provides personalized estimates of PFAS blood levels based on your drinking water exposure, covering PFOA, PFOS, PFHxS, and PFNA. It compares your estimated levels against national survey data so you can see where you fall relative to the broader population. The tool is designed to help you identify exposure sources, find ways to reduce contact, and bring useful data to a conversation with your healthcare provider.
Current Drinking Water Limits
In April 2024, the EPA finalized its first-ever enforceable limits for PFAS in drinking water. The maximum contaminant levels are set at 4.0 parts per trillion for PFOA and 4.0 parts per trillion for PFOS, individually. To put that in perspective, one part per trillion is roughly equivalent to a single drop of water in 20 Olympic swimming pools. These limits are extremely low because the chemicals accumulate in the body over time, so even tiny daily doses add up.
Water systems across the country are now required to test for these compounds and treat their water if levels exceed the new limits. If you live near a known AFFF-impacted site, checking whether your water utility has tested for PFAS is a practical first step. Private well owners in these areas may need to arrange independent testing, since the EPA rule applies to public water systems.
The Transition Away From AFFF
The military and aviation industries are in the process of moving to fluorine-free foam (F3). In January 2023, the Department of Defense published a new military specification for F3, and Congress required that qualified products be available by October 2023. The FAA has said it will accept these new fluorine-free foams at certificated airports alongside traditional AFFF.
The transition is not mandatory for civilian airports yet. The FAA has not required airports to switch, leaving the decision to individual facilities for now. This means AFFF is still in active use at many locations, and the legacy contamination from decades of prior use will persist in groundwater for the foreseeable future. The chemicals earned the name “forever chemicals” because they don’t break down naturally, so even after the last drop of AFFF is phased out, the environmental and health consequences will continue for years.