AFFF is a specialized fire suppressant widely used since the 1960s by the U.S. military, aviation industries, and civilian fire departments. This foam is highly effective at extinguishing high-hazard, flammable liquid fires, such as jet fuel or petroleum, which are known as Class B fires. AFFF is designed to rapidly spread a film over the fuel surface to cut off the oxygen supply and prevent re-ignition. The compounds responsible for this effectiveness have, however, led to significant public health and environmental concerns due to their chemical structure. The core issue is that AFFF contains Per- and Polyfluoroalkyl Substances (PFAS), a class of synthetic chemicals now subject to intense scrutiny.
Defining AFFF and Its Core Components
AFFF is typically sold as a concentrate, often mixed with water at a ratio of 3% or 6%, and is composed of fluorosurfactants, hydrocarbon surfactants, solvents, and water. The fluorinated surfactants are the functional ingredients that give the foam its low surface tension, allowing it to spread quickly and form the aqueous film that smothers the fire. This unique film-forming ability is directly attributed to the presence of PFAS.
PFAS are a large family of man-made chemicals characterized by a chain of carbon atoms bonded to fluorine atoms. This carbon-fluorine bond is one of the strongest in organic chemistry, which is why these substances do not break down naturally in the environment or the human body and have been branded “forever chemicals.” The original AFFF formulations, produced until the early 2000s, predominantly contained Perfluorooctane Sulfonate (PFOS).
Following the phase-out of PFOS production by major manufacturers, newer AFFF products began using shorter-chain PFAS, such as those based on fluorotelomers, which can still break down into other concerning compounds like Perfluorooctanoic Acid (PFOA). Both PFOS and PFOA are long-chain PFAS that have been extensively studied and are known for their persistence, potential to bioaccumulate, and toxicity.
Primary Pathways of Human Exposure
The PFAS contained within AFFF can enter the human body through several distinct routes, often stemming from the foam’s use in training and emergency situations. The most common pathway for public exposure is through contaminated drinking water. When AFFF is discharged, the chemicals seep into the ground, contaminating groundwater and surface water, particularly near military bases, airports, and firefighter training facilities where the foam was regularly used for practice exercises and equipment testing.
A second major pathway is occupational exposure, which significantly affects military personnel, firefighters, and industrial workers. These individuals experience direct exposure through inhalation of the foam mist, skin contact during handling, and ingestion of small amounts during training or emergency response. The use of AFFF in training without proper containment measures historically led to repeated, high-level contact for these professional groups.
Indirect exposure, although less common than water contamination, occurs when PFAS enters the food chain. The chemicals can accumulate in aquatic organisms after AFFF runoff enters water bodies, leading to bioaccumulation in fish and wildlife. If contaminated fish or crops grown in contaminated soil or irrigated with contaminated water are consumed, the PFAS can then be transferred to humans.
Known Health Outcomes Linked to Exposure
PFAS compounds from AFFF are known to accumulate in the human body over time, a process called bioaccumulation, where they are found in tissues such as the liver, kidneys, and blood. This persistence is a primary concern, as it leads to chronic exposure and is linked to a range of adverse health effects. Scientific and epidemiological studies have consistently linked elevated levels of PFAS exposure to an increased risk of certain cancers. Specifically, there is evidence suggesting a link between PFAS exposure and higher rates of kidney and testicular cancer.
Other cancers implicated include bladder, prostate, and thyroid cancers. The mechanism of harm involves the disruption of normal cellular functions, which can lead to cellular mutations and abnormal cell growth. Beyond cancer, PFAS exposure is associated with endocrine disruption, particularly affecting the thyroid gland. This interference with thyroid hormone function can lead to thyroid disease, which regulates metabolism and development.
Immune system suppression is another documented outcome, which may reduce the body’s ability to fight off infections and potentially increase susceptibility to diseases. Reproductive and developmental issues are also a concern, as exposure has been linked to hormonal imbalances. This includes increased risk for high blood pressure and pre-eclampsia in pregnant women, as well as decreases in infant birth weight. Liver damage, elevated cholesterol levels, and changes in liver enzymes are further health consequences that have been observed in individuals with significant PFAS exposure.
Environmental Persistence and Regulatory Responses
The extreme stability of the carbon-fluorine bond makes AFFF contamination a long-term environmental problem. Once released, PFAS chemicals can remain in soil and water sources for decades, resisting natural degradation processes. This persistence leads to the widespread contamination of groundwater and surface water, which is challenging to clean up.
Regulatory bodies have responded to this challenge by setting standards and guidelines for PFAS in the environment. The U.S. Environmental Protection Agency (EPA) has established health advisory levels for PFAS in drinking water and is working toward setting enforceable standards. This action reflects the need to manage the risk associated with widespread contamination.
Many contaminated sites, particularly former military bases and airports, are undergoing investigation and cleanup. These efforts often fall under federal guidance, addressing the environmental fallout and the sheer scale of the contamination. Furthermore, the Department of Defense is working to phase out the use of PFAS-containing firefighting foam entirely, and many states are moving to ban AFFF use to mitigate future environmental releases.