PFOS: The Main Chemical in AFFF Causing Cancers

Perfluorooctane sulfonic acid (PFOS) is a highly toxic and persistent chemical that was widely used in firefighting foams (AFFF), stain-resistant fabrics, food packaging, and industrial applications for decades. As a member of the per- and polyfluoroalkyl substances (PFAS) family, PFOS does not break down easily, leading to long-term environmental contamination and serious health risks for humans and wildlife.

PFOS and PFOA often go hand-in-hand; but unlike PFOA (which was commonly found in nonstick cookware and waterproof fabrics), PFOS was the dominant chemical in firefighting foams used by the military, airports, and fire departments to suppress fuel-based fires. Over time, it became evident that PFOS was leaching into drinking water supplies, contaminating entire communities.

This article examines the history of PFOS in firefighting foams, the industries responsible for contamination, health risks, regulatory actions, and the growing number of lawsuits seeking justice for those affected.

Aqueous film-forming foam (AFFF) containing PFOS was developed in the 1960s and became the standard for fire suppression at military bases, airports, and industrial sites.

• Superior Fire Suppression: PFOS allowed AFFF to create a thin film over burning fuel, quickly extinguishing fires and preventing re-ignition.
• Thermal and Chemical Stability: Unlike traditional foams, PFOS-based AFFF remained effective under extreme heat and hazardous conditions.
• Long-Lasting and Water-Resistant: PFOS made firefighting foams more durable, allowing them to cover surfaces and prevent fuel vapors from igniting again.

Unfortunately, PFOS is also highly mobile in water, meaning that once AFFF is used, it tends to seep into soil, groundwater, and drinking water supplies. This led to widespread contamination — especially on military bases and firefighter training sites.

PFOS is a bioaccumulative and toxic chemical that has been detected in human blood samples worldwide. Exposure is primarily linked to contaminated drinking water, occupational hazards, and firefighting foam use.

Studies have associated PFOS exposure with the following health conditions:

• Kidney Cancer: PFOS accumulates in kidney tissues, disrupting cell function and promoting tumor growth. Unlike PFOA, which primarily damages kidney tubules, PFOS exposure is linked to chronic kidney disease and renal cell carcinoma due to oxidative stress and immune suppression.
• Testicular Cancer: Firefighters and military personnel exposed to PFOS-based foams have shown elevated risks of testicular tumors. PFOS may interfere with testosterone production, leading to abnormal cell proliferation in the testes.
• Liver Cancer: PFOS disrupts liver function by altering bile acid metabolism and promoting fatty liver disease. This increases inflammation and can lead to liver fibrosis, cirrhosis, and liver cancer over time.
• Thyroid Cancer: Unlike PFOA, which primarily disrupts metabolic processes, PFOS is more strongly linked to thyroid dysfunction. It binds to thyroid transport proteins, leading to hormone imbalances and increased risk of thyroid malignancies.
• Non-Hodgkin’s Lymphoma: Epidemiological studies suggest that PFOS exposure suppresses immune function, which can lead to abnormal lymphocyte growth and increase the risk of lymphatic cancers, such as non-Hodgkin’s lymphoma.
• Brain Cancer: Emerging research indicates that PFOS may disrupt the blood-brain barrier, allowing toxic compounds to accumulate in brain tissue. This has been linked to glioblastoma and other aggressive brain tumors, particularly in individuals with prolonged PFOS exposure through contaminated drinking water or occupational hazards.

• Chronic Inflammation in the Gut: PFOS has been linked to disruptions in gut microbiota, leading to chronic inflammation and damage to the intestinal lining.
• Increased Risk of Ulcerative Colitis: Unlike PFOA, which primarily affects kidney and liver function, PFOS exposure has been associated with a higher incidence of inflammatory bowel diseases (IBD), particularly ulcerative colitis.
• Digestive Disruptions: PFOS exposure has been found to affect nutrient absorption and increase gastrointestinal distress, leading to abdominal pain, diarrhea, and long-term bowel dysfunction.

• Neurotoxic Effects: PFOS exposure has been linked to nerve damage and disruptions in neurotransmitter function, contributing to cognitive decline and motor impairments.
• Increased Risk of Parkinson’s Disease: Unlike PFOA, which primarily affects metabolic and organ function, PFOS has been shown to accumulate in the brain, leading to dopaminergic neuron damage, a key factor in Parkinson’s disease.
• Cognitive Decline and Memory Issues: Studies have found that PFOS exposure is associated with higher risks of neurodegenerative diseases, including early onset dementia and movement disorders.

• Weakened Response to Vaccines: Unlike PFOA, which affects organ toxicity, PFOS directly weakens antibody production, reducing vaccine effectiveness in children and adults.
• Increased Autoimmune Disorders: PFOS disrupts immune system signaling, increasing the risk of thyroid disease, lupus, rheumatoid arthritis, and inflammatory disorders. Unlike PFOA, which is more associated with thyroid autoimmunity, PFOS leads to broader immune suppression.
• Higher Susceptibility to Infections: PFOS-exposed individuals show decreased white blood cell activity, leading to higher risks of pneumonia, chronic bronchitis, and other persistent infections.

• Birth Defects and Low Birth Weight: PFOS crosses the placenta more easily than PFOA, directly impacting fetal development. Studies have shown that higher PFOS levels in pregnant women lead to neurological impairments, growth deficiencies, and congenital abnormalities.
• Hormonal Disruptions: PFOS interferes with the endocrine system, reducing levels of estrogen, testosterone, and thyroid hormones, leading to irregular menstrual cycles, infertility, and early menopause.
• Neurodevelopmental Issues: Unlike PFOA, which primarily affects liver and kidney function, PFOS has been linked to autism spectrum disorders, ADHD, and cognitive delays in children.
• Increased Risk of Miscarriages: Women exposed to high PFOS levels have shown higher rates of pregnancy loss and complications, likely due to its effects on placental function and fetal growth.

• High Cholesterol and Triglycerides: Unlike PFOA, which primarily affects kidney filtration, PFOS is more strongly associated with lipid metabolism disorders. It increases LDL (bad cholesterol) and triglyceride levels, leading to a higher risk of heart disease.
• Hypertension and Heart Disease: Studies have found that PFOS interferes with vascular function and nitric oxide production, increasing the risk of hypertension, heart attacks, and stroke.
• Increased Risk of Diabetes: Unlike PFOA, PFOS is strongly associated with insulin resistance and metabolic syndrome, increasing the likelihood of developing Type 2 diabetes and obesity-related complications.

As the evidence of PFOS toxicity mounted, governments worldwide implemented bans and restrictions on its use.

• 2006: The U.S. phased out PFOS production under the EPA’s PFAS Stewardship Program.
• 2016: The EPA issued a Lifetime Health Advisory (LHA) for PFOS in drinking water at 70 parts per trillion (ppt).
• 2023: The EPA proposed a maximum contaminant level (MCL) of 4 ppt, signaling stricter water safety standards.

• European Union: PFOS has been listed as a restricted substance under REACH regulations.
• Stockholm Convention (2009): PFOS was designated as a persistent organic pollutant (POP), requiring global phase-out efforts.
• Australia & Canada: Both countries have introduced water quality standards and contamination cleanup mandates.

As scientific evidence linking PFOS exposure to severe health conditions continues to grow, lawsuits against chemical manufacturers, the military, and companies responsible for contamination are mounting.

Currently, there is an active multi-district litigation (MDL) consolidated in a South Carolina Federal Court which will oversee all AFFF-related injury claims, nationwide.

• Firefighters, military personnel, and airport workers who were regularly exposed to AFFF.
• Residents near military bases and industrial sites with confirmed PFOS water contamination.
• Individuals diagnosed with cancers, ulcerative colitis, Parkinson’s disease, or immune-related illnesses linked to PFOS exposure.

Victims of PFOS exposure may be eligible for:

• Medical expenses and future treatment costs
• Lost wages and disability compensation
• Pain and suffering damages
• Punitive damages against negligent corporations

Legal experts expect multi-billion-dollar settlements as AFFF lawsuits progress, with increasing recognition of PFOS’s role in severe health conditions.

PFOS has left a lasting legacy of contamination, particularly for firefighters, military personnel, and communities near industrial sites. While bans and legal actions have pushed manufacturers to phase out PFOS-based products, the health and environmental consequences remain.

With ongoing lawsuits, stricter regulations, and growing awareness, those exposed to PFOS-contaminated water and firefighting foam may have legal recourse and compensation options. As research continues, holding corporations accountable and ensuring long-term water safety will be critical in mitigating PFOS-related health risks.