Perfluorooctane sulfonate (PFOS) is a “forever chemical,” also known as a per- and polyfluoroalkyl substance (PFAS). These synthetic compounds are notable for their persistence and widespread presence throughout global environments. Historically, PFOS found extensive application across various consumer and industrial products due to its unique chemical properties.
Understanding Perfluorooctane Sulfonate
PFOS is a synthetic chemical that originated in the mid-20th century, characterized by an eight-carbon fluorocarbon chain and a sulfonic acid functional group. It is a perfluorosulfonic acid. Its strong carbon-fluorine bonds contribute to extreme stability and persistence in the environment.
The compound exhibits exceptional properties, including the ability to repel both water and oil, as well as high heat resistance. These qualities led to its widespread use in numerous applications. PFOS was a primary ingredient in stain and water repellents like Scotchgard, and it was also found in firefighting foams, specifically Aqueous Film Forming Foam (AFFF). It was also incorporated into non-stick coatings, various industrial surfactants, and impregnation agents for textiles, paper, and leather.
Sources and Pathways of Exposure
PFOS enters the environment through various routes, primarily stemming from industrial activities and product disposal. Industrial discharges from manufacturing facilities, releases from wastewater treatment plants, and leachate from landfills are significant contributors. Sites where firefighting foams (AFFF) were used, such as military bases, airports, and firefighter training facilities, are also major sources of environmental contamination.
Once released, PFOS spreads through environmental pathways, contaminating drinking water sources, soil, and air. Its persistence allows it to travel long distances before deposition. Humans can be exposed through ingesting contaminated drinking water and food, particularly fish and shellfish that have accumulated PFOS. Inhalation of indoor air, especially dust from consumer products like carpets and upholstered furniture, also contributes to exposure.
Health and Environmental Implications
Exposure to PFOS has been linked to several adverse effects on human health. Studies suggest links with elevated cholesterol levels and liver damage. There is also evidence of immune system suppression, including a reduced response to vaccines, particularly in infants and children.
Further research suggests links to thyroid disruption and developmental effects in children, such as low birth weight, accelerated puberty, and bone variations. Exposure may also increase the risk of certain cancers, including kidney and testicular cancers. PFOS accumulates in wildlife across various trophic levels, including polar bears, marine mammals, and birds, disrupting ecological balance.
Mitigation and Prevention
Efforts to address PFOS contamination and reduce exposure involve regulatory actions and voluntary initiatives. The U.S. Environmental Protection Agency (EPA) has taken steps, including setting a national, legally enforceable drinking water standard for PFOS at 4.0 parts per trillion (ppt) in April 2024. The EPA also designated PFOS as a hazardous substance under the Comprehensive Environmental Response, Compensation, and Liability Act (Superfund) to promote cleanup efforts.
International agreements also play a role, with the Stockholm Convention on Persistent Organic Pollutants listing PFOS for global elimination or restriction in May 2009. This convention aims to prevent or minimize human exposure and environmental releases. Major manufacturers voluntarily phased out PFOS production in the early 2000s, though some existing stocks of PFOS-based firefighting foams may still be in use. Individuals can minimize exposure by considering water filters certified to remove PFAS, checking product labels for “PFAS-free” claims, and avoiding older non-stick cookware or stain-resistant fabrics that might contain PFOS.