What Is PFOS and Where Is It Found?

What does PFOS stand for?

PFOS refers to perfluorooctane sulfonic acid. It is one of the earliest and most widely produced chemicals in the PFAS group. PFOS contains a chain of carbon atoms bonded to fluorine, forming a structure that is exceptionally stable. Scientists often refer to PFOS and related compounds as “forever chemicals” because these bonds are so strong that the substances barely degrade in the environment.

Various industries found PFOS useful because it could repel water and other liquids, making it ideal for fire-resistant foams and protective coatings. The robust carbon-fluorine chemical bond that defines PFOS is also what raises persistent environmental questions. Cleanup of PFOS contamination poses a significant challenge because typical degradation processes do not work effectively on it, according to the U.S. Environmental Protection Agency (EPA).

Some health experts caution that while PFOS has been replaced in certain applications, thousands of similar PFAS remain in circulation. For anyone seeking a deeper introduction to PFAS as a whole, our broader overview at what is pfas covers the different family members and their common characteristics.

What was PFOS used for?

PFOS was used in a broad range of commercial and consumer goods from the 1950s onward. One of its most well-known applications was in stain-resistant carpeting and upholstery. Many fabric treatments contained PFOS to deter spills and extend product life. Paper food packaging, such as grease-resistant food wrappers, also commonly used PFOS coatings.

Firefighting foams were another significant use. In particular, PFOS-based aqueous film-forming foams (AFFF) became standard at airports and military bases because they so effectively smothered flammable liquid fires. Industrial sites that dealt with specialized metal plating or semiconductor manufacturing sometimes relied on PFOS as a surfactant.

These convenient uses carried a hidden cost. Research indicates that PFOS can migrate from industrial discharge areas into local water systems. Once in the environment, PFOS persists for many years, cycling through soil, water, and eventually living organisms. If you want to see whether PFOS or other PFAS have been detected regionally, our pfas contamination map might provide insight.

Why was PFOS so widely produced?

The principal reason PFOS was mass-produced for so long lies in its chemical properties. Because it is water-, oil-, and heat-resistant, PFOS solved many manufacturing and consumer needs in one go. Inventors viewed PFOS as a sort of “miracle coating” capable of boosting product longevity and market appeal.

By the 1970s and 1980s, PFOS-based treatments were in dozens of household products. Regulatory awareness of the potential environmental impact was limited at first, so manufacturers faced few barriers. This meant PFOS and related PFAS could freely flood global markets, with little oversight to ensure safe disposal or thorough environmental controls.

As awareness of PFOS contamination grew, scientific studies linked this chemical to concerns including liver damage, immune effects, and other potential adverse outcomes. The conversation shifted to liability and who would bear the costs of environmental cleanup. Some industries voluntarily phased out PFOS in the early 2000s, but by that time, these substances had already made their way into ecosystems worldwide.

Is PFOS still in use today?

In many countries, PFOS usage has declined significantly. For example, the European Union has imposed restrictions under its Persistent Organic Pollutants regulation, and some United States industries moved away from using PFOS by the mid-2000s. Japan also prohibited the manufacture and use of certain chemicals in the PFOS family in 2020. However, PFOS remains in older products and may still be manufactured in regions with less stringent controls.

Despite regulations, legacy contamination persists. Items produced decades ago can continue to release PFOS into air, dust, and water as they degrade. Certain consumer goods and industrial materials stored in warehouses might also still contain PFOS-based coatings. On top of that, thousands of other PFAS compounds are in circulation, some with properties similar to PFOS, and the scientific community continues to evaluate their safety.

If you have ongoing concerns about potential PFOS problems where you live, you can consider testing or remediation options. Our pfas testing lab reference page outlines how specialized testing services can detect minute concentrations in water or soil. We also recommend exploring solutions like pfos water filter technologies designed specifically to reduce PFOS levels in residential water systems.

Where is PFOS most commonly found?

Drinking water and groundwater

PFOS contamination often appears in municipal water supplies and private wells if industrial discharge, landfill leachate, or firefighting foam runoff infiltrates groundwater. The Centers for Disease Control and Prevention (CDC) indicates that communities located near or downstream from these sites may face higher PFOS exposure. For context, if you suspect water contamination, you could compare local data using a resource like our pfas in drinking water guide.

Firefighting foam sites (airports, military bases)

Airport firefighting training grounds are often flagged as PFOS hotspots. Decades of using PFOS-containing foam to extinguish or practice extinguishing jet-fuel fires has led to extensive soil and groundwater contamination. Military bases also share a similar history. Government-led cleanup projects are underway in some locations, but large-scale remediation can be slow and costly.

Industrial discharge areas

Manufacturing facilities that once relied on PFOS in metal plating, textile finishing, or plastics production sometimes discharged PFOS-laden water. Although regulations have tightened, older sites may still be releasing PFOS. Nearby communities are at heightened risk of exposure when living near these industrial zones, especially if local soil and groundwater have not been fully rehabilitated.

Household products (older fabrics, carpets, food packaging)

Prior to the mid-2000s, many stain-resistant carpets, nonstick cookware, and grease-proof food wrappers contained PFOS. Over time, wear and tear can release dust particles laced with PFOS into indoor air. People who live in older homes or who keep older household goods may unknowingly come into contact with residues. If you notice unusual stains or coatings on vintage household products, it might be worth investigating further.

How are people exposed to PFOS?

Residents living near contaminated sites may ingest PFOS through drinking water or locally grown produce. According to the CDC, even fish from PFOS-contaminated lakes and rivers can carry elevated PFOS levels. Indoor air exposure is possible too, particularly if older carpets or furniture are shedding dust laden with PFOS.

Diet is another factor. Certain food packaging materials historically used PFOS-based grease barriers. Although many manufacturers have phased out these coatings, older packaging stock might still be in circulation in some areas. Direct contact, such as handling PFOS-containing items or working in industries where PFOS is used, can also lead to higher-than-average blood levels.

Below is a general summary of possible PFOS exposure pathways:

• Drinking water from contaminated municipal or private wells

• Eating fish caught in contaminated lakes or rivers

• Inhaling household dust from older carpets or textiles

• Consuming food packaged in older PFOS-treated materials

• Working on industrial processes that handle PFOS-based products

What are the health risks of PFOS exposure?

Several health agencies, including the EPA, have documented findings suggesting that elevated PFOS levels may be associated with effects on liver and kidney function, immune response, and developmental factors in infants. Children may be particularly vulnerable because they can ingest or inhale greater concentrations relative to their body weight. Studies by the CDC show that even small amounts of PFOS can accumulate in the bloodstream over time.

According to the International Agency for Research on Cancer (IARC), PFOS is classified as “possibly carcinogenic to humans.” Some research points to potential associations with testicular and kidney cancers, though these findings are still under evaluation. For an overview of these possible connections, our pfas and cancer page discusses links between PFAS exposure and various cancers, including the controversies around how strong the evidence is.

Health departments in multiple countries are investigating long-term health implications. Some of the commonly cited conditions linked to PFOS exposure include:

• Liver damage

• Hormonal and reproductive disruptions

• Immunological impacts (including potential lowered vaccine response)

• Possible increased risk of kidney, testicular, or other cancers

While many factors go into diagnosing specific health issues, it is clear that PFOS, like other PFAS, can linger in our blood for extended periods, increasing the potential for cumulative effects.

Can PFOS be found in blood tests?

Yes. Medical professionals use specialized tests to detect PFOS in a blood sample. These tests measure how much PFOS has accumulated, offering insights into potential long-term exposure. Studies conducted by the CDC’s National Health and Nutrition Examination Survey (NHANES) have consistently found PFOS in the blood of most participants, although levels vary widely by area and lifestyle.

Blood testing is not a routine procedure and is usually recommended for individuals with high potential exposure (for example, those living near a contaminated site or working with PFOS). If you are considering such testing, it helps to discuss the matter with a healthcare provider who can aid in interpreting the results in the context of your health profile. Be aware that even if your PFOS level is elevated, medical experts may not have a precise treatment to eliminate PFOS from your system, because it does not break down easily.

Are there regulations on PFOS?

Regulations have strengthened over the past two decades. The European Union effectively banned most PFOS uses under the Persistent Organic Pollutants regulation, aiming to reduce environmental and human exposure. Canada has taken a similar approach, adding PFOS to its List of Toxic Substances. In the United States, the EPA has proposed or enacted rules to limit PFAS discharges in industrial effluent and mandated more comprehensive reporting for the import or manufacture of PFOS-containing products under the Toxic Substances Control Act (TSCA).

According to the EPA’s January 2023 proposal, companies that have produced or imported PFOS since 2011 must report these activities. The rationale is to track usage patterns, better estimate environmental burdens, and facilitate cleanup efforts. Globally, the future may hold even stricter PFOS standards. The growing wave of international attention suggests that if you are producing, importing, or using PFOS, you will likely face further regulatory constraints.

If you suspect PFOS contamination in your community or have suffered health issues that you believe trace back to PFOS exposure, you may want to explore legal assistance. We help connect individuals to attorneys who can evaluate whether the costs of medical care and property damage are recoverable under evolving PFOS liability laws.

Frequently asked questions (FAQ)

Is PFOS the same as PFOA?

No. PFOS and PFOA (perfluorooctanoic acid) are chemically related but differ in their structure and specific uses. Both chemicals fall under PFAS. To learn more, see our article on what is pfoa.

Can home filtration remove PFOS?

Certain water filtration systems, such as activated carbon filters or reverse osmosis units, can reduce PFOS levels. For more on how filtration works, see pfos water filter or read about potential strategies at how to remove pfas from water.

What should we do if our local water supply is contaminated?

Check your local health department’s guidance and consider installing a filtration system. The EPA advises that people living in highly impacted areas may benefit from point-of-use filters. Additionally, you can stay informed on municipal testing results via the pfas in wastewater or pfas monitoring resources.

Does cooking with older nonstick cookware pose a risk?

Many older pans contained PFOS or related chemicals. If the nonstick surface is deteriorating, particles can migrate into food. Some experts recommend replacing heavily worn pans. Always follow manufacturers’ guidelines and look for PFAS-free labels if you want added peace of mind.

Where do we get help if we suspect PFOS exposure?

Start by consulting a healthcare provider for relevant testing. You may also want to check your community’s contamination status with local environmental agencies. If you believe your health issues or property contamination are linked to PFOS, a legal consultation may be an option.