Aqueous Film-Forming Foam (AFFF) is effective in extinguishing highly volatile liquid fuel fires. This specialized firefighting agent creates a film that spreads rapidly over flammable liquids, suppressing vapors and preventing reignition. Despite its widespread use and effectiveness, public concern has emerged regarding the potential link between AFFF and serious health issues, particularly cancer. Understanding the scientific foundations of these concerns is important for individuals and communities alike. This article explores AFFF’s composition, the scientific evidence connecting its chemical components to cancer, susceptible populations, and efforts to regulate and replace these substances.
Understanding AFFF and Its Components
Aqueous Film-Forming Foam (AFFF) is a fire suppression agent designed for fires involving flammable liquids like petroleum and jet fuel. It functions by forming a thin, aqueous film that effectively smothers the fire, cools the fuel, and prevents the release of combustible vapors. The foam concentrate typically consists of water, solvents like glycol ethers, hydrocarbon surfactants, and crucially, fluorosurfactants.
These fluorosurfactants are a type of Per- and Polyfluoroalkyl Substances, commonly known as PFAS. PFAS are a large group of synthetic chemicals defined by a chain of linked carbon and fluorine atoms. This robust carbon-fluorine bond is one of the strongest in organic chemistry, making PFAS highly resistant to degradation and giving them their unique properties, such as resistance to heat, oil, and water. Consequently, PFAS are often called “forever chemicals” because they persist in the environment and human bodies for extended periods, rather than breaking down naturally.
The Scientific Evidence Linking PFAS to Cancer
Scientific research and epidemiological studies demonstrate associations between PFAS exposure and various cancers. Perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) are extensively studied PFAS chemicals linked to increased cancer risk. The International Agency for Research on Cancer (IARC) classified PFOA as carcinogenic to humans (Group 1) based on sufficient evidence in animals and strong mechanistic evidence in exposed humans, while PFOS is classified as possibly carcinogenic to humans (Group 2B).
Specific cancers associated with PFAS exposure include kidney, testicular, and prostate cancers. A NASEM report found sufficient evidence linking PFAS exposure to increased kidney cancer risk.
Research also indicates possible links to:
- Ovarian cancer
- Non-Hodgkin lymphoma
- Thyroid cancer
- Ulcerative colitis (with elevated PFOA levels)
- Liver, breast, and colon cancers
- In males: leukemia, urinary system, brain, and soft tissue cancers
- In females: oral cavity and pharynx, and soft tissue cancers
The proposed mechanisms for PFAS contributing to cancer development are varied. These include hormone function disruption (endocrine disruption), relevant for hormone-dependent cancers like prostate and breast cancer. PFAS can also suppress the immune system, hindering the body’s ability to fight cancerous cells. Other mechanisms involve altered metabolic processes, leading to liver and kidney carcinogenesis. Additionally, PFAS exposure has been linked to oxidative stress and epigenetic alterations, which can promote cancer.
Exposure Risks and Affected Populations
Exposure to PFAS from firefighting foam impacts specific populations through various pathways. Firefighters are a primary at-risk group due to direct and frequent contact with AFFF during training and active fire suppression. They can be exposed through inhalation of foam mist, direct skin contact, and ingestion of contaminated dust or water within fire stations. Firefighters’ personal protective equipment, or turnout gear, also contains PFAS, leading to dermal exposure as chemicals migrate to inner layers.
Military personnel are another affected population. AFFF has been used for decades on military bases for training and managing liquid fuel fires, leading to widespread soil and groundwater contamination. This contamination can expose military members and their families through drinking water, with many military sites reporting PFAS levels exceeding safety thresholds. More than 700 U.S. military sites are known to have discharged PFAS.
Communities near military installations, industrial facilities that manufactured or used PFAS, or sites where AFFF was used for firefighting (such as airports) face elevated exposure risks. Environmental contamination of local water sources, including public drinking water systems and private wells, and air pollution are primary exposure routes for these communities.
Current Regulations and Future Directions
In response to health and environmental concerns, governments and organizations are implementing measures to regulate and phase out PFAS in firefighting foams. Many states have enacted or proposed legislation restricting the use and discharge of PFAS-containing AFFF, particularly for training purposes, with exceptions for emergency operations and testing facilities that employ containment measures.
The U.S. Department of Defense (DOD), a major user of AFFF, has mandated a transition away from PFAS-containing foams. The DOD must stop purchasing PFAS-based firefighting foams by October 1, 2023, and cease their use entirely by October 1, 2025, though waivers may extend this deadline for some uses until October 2026. The Environmental Protection Agency (EPA) has also designated PFOA and PFOS as hazardous substances under the Superfund law. The EPA has also proposed a national drinking water standard for PFOA and PFOS at 4 parts per trillion.
Significant efforts are underway to develop and implement PFAS-free alternatives, often called fluorine-free foams (F3). Researchers are exploring new formulations and additives to ensure these alternatives can match the fire suppression effectiveness of traditional AFFF, especially for challenging Class B fires. The transition presents challenges, as PFAS-free foams may not be direct “drop-in” replacements and may require modifications to equipment and training protocols. Despite these hurdles, the development and adoption of safer firefighting solutions are progressing, reflecting a global shift towards mitigating PFAS contamination.