PFOS (Perfluorooctanesulfonate) is a synthetic perfluorinated compound belonging to the broader PFAS (Per- and Polyfluoroalkyl Substances) family. It is highly persistent, bioaccumulative, and toxic, making it a major concern for human health and the environment. Due to its chemical stability and water- and oil-repellent properties, PFOS was widely used in industrial and consumer applications before its regulation and phase-out in many countries.

1. Chemical Structure and Properties

PFOS consists of a perfluorinated carbon chain (C8) with a sulfonate (-SO₃⁻) functional group, giving it:

• High chemical and thermal stability → resistant to degradation.
• Hydrophobic and lipophobic properties → repels water, oil, and grease.
• Strong surface activity → excellent surfactant properties.

Because of these characteristics, PFOS persists in the environment for decades and accumulates in human and animal tissues.

2. Industrial and Consumer Uses

Before restrictions, PFOS was used in a variety of applications:

a. Firefighting Foams

• A major ingredient in aqueous film-forming foams (AFFF) used for extinguishing flammable liquid fires (e.g., aircraft and military bases).
• Responsible for significant groundwater and soil contamination near training sites.

b. Textile and Leather Treatments

• Applied to waterproof clothing (Gore-Tex), carpets, and furniture upholstery to provide stain and water resistance.
• Found in shoes, tents, and industrial fabrics.

c. Metal Plating and Electronics

• Used in chrome plating and etching processes to reduce surface tension and chemical emissions.
• Found in semiconductors, circuit boards, and coatings for electronic devices.

d. Food Packaging and Non-stick Cookware

• Used in fast-food wrappers, greaseproof paper, and microwave popcorn bags.
• Present in Teflon (PTFE) coatings for non-stick cookware.

e. Pesticides and Household Products

• Previously used in insecticides and stain-resistant sprays for furniture and carpets.
• Found in water- and oil-resistant paper products.

3. Environmental and Health Concerns

a. Persistence and Bioaccumulation

PFOS is classified as a persistent organic pollutant (POP) due to its extreme environmental stability. It has been detected in:

• Drinking water and groundwater → contamination from industrial sites, landfills, and firefighting foam residues.
• Soil and sediments → accumulates in the environment with no natural degradation.
• Wildlife (fish, birds, marine mammals) → high concentrations in Arctic animals due to global atmospheric transport.
• Human blood and tissues → detected in nearly all tested individuals worldwide.

b. Health Effects of PFOS Exposure

Studies indicate that chronic exposure to PFOS is linked to:

1. Endocrine Disruption

• Interference with thyroid hormone regulation, affecting metabolism and development.
• Alterations in reproductive hormones, leading to fertility issues.

2. Cancer Risk

• Increased incidence of kidney, testicular, and liver cancer.
• Possible pancreatic and prostate cancer risks (under investigation).

3. Metabolic Disorders

• Elevated cholesterol and triglyceride levels.
• Increased risk of obesity and insulin resistance.

4. Immune System Suppression

• Reduced vaccine efficacy and increased susceptibility to infections.
• Potential impacts on autoimmune disorders.

5. Developmental and Reproductive Toxicity

• Low birth weight, delayed fetal development, and neurodevelopmental disorders.
• Linked to preterm births and reduced fertility in men and women.

In 2016, the U.S. EPA set a lifetime health advisory limit for PFOS in drinking water at 70 parts per trillion (ppt), but recent studies suggest even lower levels may pose risks.

4. Regulations and Bans

Due to its toxicity and persistence, PFOS has been banned or restricted in multiple countries:

• 2009 → Listed under the Stockholm Convention on Persistent Organic Pollutants, leading to a global phase-out.
• United States (EPA) → PFOA and PFOS phased out under the PFOA Stewardship Program.
• European Union (REACH Regulation) → PFOS restricted to concentrations below 0.001% in products.
• Canada, Australia, and Japan → PFOS phased out, but contamination remains in older products and industrial waste.

5. How to Reduce PFOS Exposure?

• Avoid using non-stick cookware (Teflon) if scratched or damaged.
• Limit consumption of packaged fast food that may use grease-resistant wrappers.
• Check water quality reports and use activated carbon filters to reduce PFOS contamination.
• Choose PFAS-free alternatives for clothing, carpets, and furniture.
• Be cautious with cosmetics and personal care products that may contain PFAS.

6. Conclusion

PFOS is a highly toxic, persistent, and bioaccumulative substance that poses significant environmental and health risks. While it has been banned in many countries, its contamination remains widespread due to legacy pollution and long-lasting environmental persistence. Ongoing research and regulatory efforts are crucial to mitigate exposure and find safer alternatives.