PFOA

PFOA
Name	Perfluorooctanoic acid
IUPACName	Pentadecafluorooctanoic acid
OtherNames	C8, Perfluorocaprylic acid, PFOA

PFOA. It is a synthetic, fully fluorinated carboxylic acid and a key member of the broader class of per- and polyfluoroalkyl substances. This chemical compound gained widespread industrial use in the mid-20th century due to its unique surfactant properties. Its environmental persistence and associated health risks have led to significant regulatory action and extensive scientific study.

Chemical properties and structure

The molecule consists of a seven-carbon fluorocarbon chain terminated with a carboxylate group, where all hydrogen atoms are replaced by fluorine. This perfluorinated structure creates an extremely strong carbon–fluorine bond, one of the strongest in organic chemistry, which confers exceptional thermal and chemical stability. The hydrophobic fluorinated tail and hydrophilic acid head make it an effective surfactant, capable of reducing surface tension in both aqueous and organic media. Its pKa is approximately -0.5, meaning it exists almost entirely in its anionic form, perfluorooctanoate, under environmental and physiological conditions, contributing to its high mobility in water and within living organisms.

Production and uses

Historically, PFOA was manufactured primarily via electrochemical fluorination, a process developed by the Minnesota Mining and Manufacturing Company. It served as a critical processing aid in the production of polytetrafluoroethylene, famously known by the E. I. du Pont de Nemours and Company brand name Teflon. Its primary function was to stabilize fluoropolymer dispersions during the manufacturing of non-stick cookware coatings, waterproof clothing, and stain-resistant carpets. It was also a key ingredient in aqueous film-forming foam used for fighting fuel fires at locations like military bases and airports.

Environmental presence and persistence

Due to its widespread use and resistance to degradation, PFOA has become a global contaminant. It has been detected in drinking water supplies, notably in communities near industrial sites like those involved in the Washington Works plant in West Virginia. Its environmental persistence is remarkable, with an estimated half-life in water of over 90 years; it does not break down via typical natural processes like hydrolysis, photolysis, or biodegradation. The compound undergoes long-range transport, leading to its accumulation in remote regions such as the Arctic and has been found in wildlife including polar bears, bald eagles, and fish.

Health effects and toxicology

Epidemiological studies, such as the C8 Science Panel research linked to the Ohio River Valley, have associated exposure with several adverse health outcomes. In humans, it is linked to elevated cholesterol, ulcerative colitis, thyroid disease, and preeclampsia. Animal studies conducted by agencies like the United States Environmental Protection Agency have shown it causes hepatotoxicity, immunotoxicity, and promotes tumors in the liver, pancreas, and testes of rodents. The substance is readily absorbed following oral exposure, binds to serum albumin in the blood, and has a very long half-life in the human body, estimated between two to four years.

Regulation and phase-out

Major regulatory action began in the early 21st century following litigation and scientific scrutiny. The United States Environmental Protection Agency launched the 2010/2015 PFOA Stewardship Program, securing commitments from major manufacturers like DuPont and 3M to eliminate its use and emissions. The Stockholm Convention on Persistent Organic Pollutants listed PFOA for global elimination in 2019, with specific exemptions for certain applications. In the United States, the Safe Drinking Water Act has been used to establish health advisories, and states like Vermont and California have enacted their own stringent regulations.

Alternatives and remediation

Industry has shifted towards shorter-chain perfluoroalkyl substances, such as GenX chemicals, though these alternatives also face environmental and health scrutiny. Remediation of contaminated sites is challenging; effective technologies include using granular activated carbon filtration at water treatment plants, like those installed in Hoosick Falls, New York. Advanced methods being researched include sonochemical degradation and specialized microbial degradation processes. Ongoing research by institutions like the University of Rhode Island focuses on developing non-fluorinated, safer chemical alternatives for essential applications.

Category:Perfluorinated compounds Category:Persistent organic pollutants Category:Surfactants