What are PFAS and why are they called forever chemicals?

PFAS are a class of over 14,000 synthetic fluorinated compounds characterized by fully or partially fluorinated carbon chains¹. The carbon-fluorine bond -- the strongest single bond in organic chemistry -- gives these molecules extraordinary thermal and chemical stability. This is precisely what makes them useful in industrial applications and precisely what makes them persistent environmental contaminants.

The two most extensively studied PFAS are PFOA (perfluorooctanoic acid) and PFOS (perfluorooctane sulfonic acid), both of which have been phased out of production in the U.S. but remain widespread in the environment and in human blood². Newer "short-chain" replacements like GenX were introduced as safer alternatives, but emerging research suggests they carry their own risks³.

Major exposure pathways include contaminated drinking water (especially near military bases and industrial sites that used firefighting foam), food packaging, nonstick cookware, and occupational exposure in manufacturing³. The CDC's National Health and Nutrition Examination Survey has detected PFAS in the blood of nearly all Americans tested.

The sheer scale of PFAS contamination is difficult to overstate. A 2022 study published in Environmental Science & Technology by Cousins et al. concluded that PFAS contamination of rainwater globally has exceeded safe planetary boundaries⁴. Rainwater virtually everywhere on Earth now contains PFAS levels that exceed the most protective drinking water guidelines, including the EPA's interim health advisory of 0.004 ppt for PFOA and 0.02 ppt for PFOS set in 2022.

The chemical basis for PFAS persistence lies in the C-F bond dissociation energy of approximately 536 kJ/mol, compared to 411 kJ/mol for C-H bonds¹. No naturally occurring biological or environmental process efficiently degrades these bonds at ambient conditions. PFAS resist photolysis, hydrolysis, biodegradation, and atmospheric oxidation -- making them among the most persistent anthropogenic chemicals ever created.

PFAS bioaccumulate through food chains and have half-lives in the human body ranging from about 2-8 years for long-chain compounds like PFOA and PFOS³. While some shorter-chain PFAS are cleared more quickly, their widespread and continuous exposure means body burdens remain elevated even after source removal. The EPA estimates that PFAS contamination affects drinking water for over 100 million Americans².