Per- and polyfluoroalkyl substances (PFAS or PFASs) are a group of synthetic organofluorine chemical compounds that have multiple fluorine atoms attached to an alkyl chain. An early definition, from 2011, required that they contain at least one perfluoroalkyl moiety, –CnF2n+1–. Beginning in 2021, the Organisation for Economic Co-operation and Development (OECD) expanded their terminology, stating that "PFASs are defined as fluorinated substances that contain at least one fully fluorinated methyl or methylene carbon atom (without any H/Cl/Br/I atom attached to it), i.e. with a few noted exceptions, any chemical with at least a perfluorinated methyl group (–CF3) or a perfluorinated methylene group (–CF2–) is a PFAS."
According to the OECD, at least 4,730 distinct PFASs that contain at least three perfluorinated carbon atoms are known. The United States Environmental Protection Agency's (EPA) toxicity database, DSSTox, lists 14,735 unique PFAS chemical compounds, while PubChem lists approximately 6 million. The fluorinated surfactants or fluorosurfactants subgroup has a fluorinated "tail" and a hydrophilic "head" and are thus considered surfactants. These are more effective at reducing the surface tension of water than comparable hydrocarbon surfactants. They include the perfluorosulfonic acids, such as perfluorooctanesulfonic acid (PFOS), and the perfluorocarboxylic acids like perfluorooctanoic acid (PFOA).
Many PFASs were used in the mid-20th century in products and on materials due to their enhanced water-resistant properties, such as within Teflon or aqueous film forming foam. Only since the start of the 21st century has the environmental impact and toxicity to human and mammalian life been studied in depth. PFOS, PFOA and other PFASs are commonly described as persistent organic pollutants or "forever chemicals" because they remain in the environment for long periods of time. Residues have been detected in humans and wildlife, prompting concern about impacts to health.
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Persistent organic pollutants (POPs) are organic compounds that are resistant to degradation through chemical, biological, and photolytic processes. They are toxic chemicals that adversely affect human health and the environment around the world. Because they can be transported by wind and water, most POPs generated in one country can and do affect people and wildlife far from where they are used and released.
Public water system is a regulatory term used in the United States and Canada, referring to certain utilities and organizations providing drinking water. The US Safe Drinking Water Act and derivative legislation define "public water system" as an entity that provides "water for human consumption through pipes or other constructed conveyances to at least 15 service connections or serves an average of at least 25 people for at least 60 days a year." The term "public" in "public water system" refers to the people drinking the water, not to the ownership of the system.
Emulsion polymerization is a type of radical polymerization that usually starts with an emulsion incorporating water, monomer, and surfactant. The most common type of emulsion polymerization is an oil-in-water emulsion, in which droplets of monomer (the oil) are emulsified (with surfactants) in a continuous phase of water. Water-soluble polymers, such as certain polyvinyl alcohols or hydroxyethyl celluloses, can also be used to act as emulsifiers/stabilizers. The name "emulsion polymerization" is a misnomer that arises from a historical misconception.
Delves into the history and impact of PFOA, a dangerous molecule causing severe contamination and health issues.
Delves into the impact of endocrine disruptors on human health and wildlife, exploring how these substances interfere with hormonal pathways.
Explores Persistent Organic Pollutants (POPs) sources, bioaccumulation potential, and toxicity, focusing on PAHs and pesticides impact on the environment and human health.
The hollow fiber ultrafiltration (HFUF)-based microbial concentration method is widely applied for monitoring pathogenic viruses and microbial indicators in environmental water samples. However, the HFUF-based method can co-concentrate substances that inte ...
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Chemical oxidation has been applied in municipal water treatment for more than a century, initially for disinfection. In the early decades, chlorine disinfection was adopted in the fight against waterborne disease. However, the oxidative properties of chlo ...
Emulsions are omnipresent in our everyday life; for example, in food, certain drug and cosmetic formulations, agriculture, and as paints. Moreover, they are frequently used to perform high-throughput screening assays with minimum sample volumes. Key to the ...