By Dr Laura M. Labay and Dr Sherri L. Kacinko
The forever contaminants of our generation
PFAS (perfluoroalkyl and polyfluoroalkyl substances) are synthetic chemicals that have a wide range of industrial and manufacturing applications because of their chemical and thermal stability and their hydrophobic and lipophobic characteristics. PFAS are persistent in the environment, bioaccumulate in wildlife and humans, and are associated with adverse health effects including cancer, immune dysregulation, and elevated cholesterol. Because several thousand PFAS chemicals exist, knowledge about critical health effects related to PFAS is constantly developing. Biomonitoring and increased medical surveillance, when appropriate, are useful to evaluate patient-specific health risks.
What are PFAS?
Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are a heterogenous class of synthetic fluorinated compounds that have been used for decades (see Table 1 for the chemical names and abbreviations for the PFAS cited in this article). Although it is estimated that thousands of PFAS exist, two of the most well-known and widely studied are PFOA and PFOS . PFOA was first mass-manufactured in the late 1940s. Use escalated in the 1950s for the purpose of chemically coating products to create nonstick, waterproof, noncorrosive, and nonreactive surfaces. Its related compound, PFOS, was discovered soon thereafter and used as an ingredient to make various textiles water and stain repellant . Decades later, as awareness about the potentially harmful health effects associated with PFAS exposure grew within the scientific and medical communities, guidelines and policies addressing PFOA and PFOS use were formulated. In 2006, eight major companies using PFAS agreed to phase out production of PFOA and PFOA-related chemicals by 2015. In 2009, The Stockholm Convention on Persistent Organic Pollutants voted to eliminate the production and use of PFOS under most circumstances. A decade later, Stockholm Convention members banned the use of firefighting foams containing PFOA and removed exemptions for the use of PFOS . However, PFOA and PFOS were replaced with alternative shorter-chain PFAS chemicals such as PFBS and GenX, the latter of which was marketed as a “sustainable substitute for PFOA” (Fig. 1). It was postulated that they were safer because the short-chain PFAS bioconcentrate to a lesser degree and are eliminated more quickly from the body compared to the longer-chain PFAS [4,5]. Examples of consumer products that may contain PFAS include rain gear, cosmetics, stain-resistant textiles, food package coatings and cookware. Their extreme persistence in the environment and long half-lives, estimated from days to years depending on the length of the PFAS chain, have earned them the name “forever chemicals” .
Several interconnected pathways exist for the release and circulation of PFAS into the environment (Fig. 2). Primary sources of contamination are manufacturing sites that produce or use PFAS and then discharge the chemicals into surface water, wastewater and soil. The presence of PFAS in waste streams affects surface and groundwater, the two primary sources of drinking water worldwide. PFAS are recalcitrant compounds in that they are not readily degraded by light or microbial organisms. Owing to their solubilities in water and resistance to breakdown, they are persistent, environmentally mobile and challenging to mitigate and remove. They are taken up by plants and animals throughout the food chain, which further leads to bioaccumulation in fish, wildlife and humans. It is estimated that 99% of the human population have PFAS in their blood . Occupational exposure may also contribute to an increase of total PFAS body burden. Firefighters, as an example, can have significant exposure from direct contact, handling of contaminated equipment, managing foam waste, and working with foam concentrates. PFAS (e.g. PFHxS) can be present in some aqueous film-forming foam (AFFF) formulations that have been used for decades as a fire suppressant for extinguishing fires involving petroleum products or other flammable liquids. PFAS can also be present in personal protective equipment (PPE), which can carry PFAS-containing dust and particulates into firehouse work and living areas .
There are over 2100 PFAS hotspots (i.e. sites where the PFAS concentration reaches a level considered hazardous to health) in Europe and 2800 PFAS-contaminated public and private water systems in the United States of America [9,10]. Even though efforts have been made to reduce exposure through policies and regulations, complete success has been hindered. For example, oversight of environmental-toxicant regulations in the USA is not under the purview of a single authority – the Environmental Protection Agency (EPA) regulates public drinking water, the U.S. Food and Drug Administration (FDA) regulates bottled water, and private wells are not assigned to any federal agency. Furthermore, even though in March 2023, the EPA did announce the proposed National Primary Drinking Water Regulation that would limit PFAS in drinking water, this included only six PFAS (PFOA, PFOS, PFNA, Gen X chemicals, PFHxS and PFBS) .