perfluorooctanoic acid

perfluorooctanoic acid
Name	perfluorooctanoic acid
IUPACName	pentadecafluorooctanoic acid
OtherNames	PFOA, C8, perfluorooctanoate

perfluorooctanoic acid is a synthetic perfluorinated carboxylic acid and a type of per- and polyfluoroalkyl substance. It is historically significant for its use in industrial and consumer applications, most notably in the manufacture of polytetrafluoroethylene. Due to its environmental persistence and bioaccumulative potential, it has become a major global contaminant and a subject of intense regulatory scrutiny and scientific study.

Chemical properties and structure

The molecule consists of a seven-carbon fluorocarbon chain terminated by a carboxylic acid functional group. This structure, where fluorine atoms replace all hydrogen atoms on the carbon backbone, confers exceptional stability and resistance to thermal, chemical, and biological degradation. The strong carbon–fluorine bond is central to its inert properties. In aqueous systems, it typically exists in its anionic conjugate base form, known as perfluorooctanoate, which is highly soluble and mobile in the environment.

Production and uses

Perfluorooctanoic acid was manufactured primarily via electrochemical fluorination, a process developed by the 3M Company, and later through telomerization. Its principal historical use was as a processing aid, specifically as an aqueous dispersant, in the production of fluoropolymers like polytetrafluoroethylene. Major manufacturers included DuPont, which used it at facilities such as its Washington Works plant. It was also a key ingredient in the manufacture of Scotchgard and other stain-resistant coatings for textiles, carpets, and food packaging.

Environmental and human exposure

Environmental release occurred through industrial emissions, wastewater discharge, and the degradation of precursor compounds. It is now a ubiquitous global contaminant detected in water, soil, air, and biological samples. Human exposure pathways include ingestion of contaminated drinking water, notably linked to releases from facilities like the DuPont Washington Works near Parkersburg, West Virginia, and consumption of contaminated food. It has been detected in the serum of the general population in many countries, including studies by the Centers for Disease Control and Prevention.

Health effects and toxicology

Epidemiological studies and animal toxicology data have associated exposure with several adverse health outcomes. Key concerns include links to testicular cancer, kidney cancer, ulcerative colitis, and pregnancy-induced hypertension. It is also a suspected endocrine disruptor and can affect lipid metabolism and the immune system. The substance is not metabolized in the body and has a long serum half-life in humans. Major health studies were prompted by litigation surrounding the DuPont Washington Works contamination.

Regulation and phase-out

In response to growing evidence of persistence and toxicity, the United States Environmental Protection Agency initiated the PFOA Stewardship Program in 2006, securing commitments from major companies to eliminate its use and emissions. The Stockholm Convention on Persistent Organic Pollutants listed perfluorooctanoic acid for global elimination in 2019. In the United States, the Safe Drinking Water Act has been used to establish health advisories, and several states, including Vermont and California, have enacted their own stringent regulations.

Detection and analysis

Accurate measurement in environmental and biological matrices is challenging due to low detection limits required. The primary analytical technique is liquid chromatography coupled with tandem mass spectrometry. Standardized methods have been developed by agencies like the United States Environmental Protection Agency and the International Organization for Standardization. Large-scale biomonitoring efforts, such as those conducted by the National Health and Nutrition Examination Survey, have been crucial in assessing population exposure levels.

Category:Organofluorides Category:Persistent organic pollutants Category:Carboxylic acids