environment · water · health · family: the solution exists but nobody can afford it
forever chemicals withno known destroyer
No cost-effective technology exists to destroy PFAS at water treatment scale
Problem statement
Per- and polyfluoroalkyl substances (PFAS) — a class of synthetic chemicals used in firefighting foams, nonstick pans and stain-repellent fabrics, food packaging, and electronics manufacturing — have contaminated soil and water. The many fluorine atoms in PFAS give them their oil- and water-repelling properties, but the relative inertness of the carbon-fluorine bond to chemical reactions makes PFAS persist in the environment and in living organisms. Current treatment technologies can capture PFAS from water but cannot destroy them, merely concentrating the contamination into waste streams that require disposal, creating a secondary contamination problem. NSF's letter says there remains a critical national need for effective, feasible, and sustainable technologies to degrade, destroy, or permanently sequester PFAS in soil, sediment, aquatic systems, and waste streams.
Why this matters
Trang et al. (Science, 2022) write that chronic exposure to even low levels of PFAS is associated with negative health effects such as thyroid disease, liver damage, high cholesterol, reduced immune responses, low birth weights, and several cancers. The NSF letter says exposure can lead to adverse health effects, which makes removing PFAS from the environment a critically important goal. The letter does not require a full technical economic analysis, but it asks proposers to provide a basis of comparison to existing technologies, using preliminary data, theoretical arguments, or modeling, as evidence of sustainability and feasibility.
What’s been tried and why it hasn’t worked
Trang et al. (Science, 2022) describe the field this way: established adsorbents such as activated carbon and ion-exchange resins, emerging materials such as cross-linked polymers, and membrane-based separation processes remove PFAS from water but create PFAS-contaminated solid or liquid waste streams and do not address how to degrade the pollutants. Destruction is a daunting task because the strong carbon-fluorine bonds that give PFAS their desirable properties also make them resistant to end-of-life degradation, and the harsh degradation methods in use include incineration, ultrasonication, plasma-based oxidation, electrochemical degradation, supercritical water oxidation, and ultraviolet-initiated degradation using additives such as sulfite or iron. Current destruction strategies, they write, use nonselective destruction mechanisms. The NSF letter locates the difficulty in the extreme chemical stability of many PFAS compounds, including PFOA and PFOS, which results in recalcitrance to biodegradation, photo-oxidation, direct photolysis, and hydrolysis; the letter itself does not catalogue existing technologies or say why each falls short, and asks proposers to supply that comparison.
What would unlock progress
The NSF letter names three priority topics: research that enables technologies for the mitigation, remediation, or treatment of PFAS in the environment; research that elucidates the underlying limitations of PFAS transformation reactions and could lead to potentially transformative, feasible technologies; and research that identifies biological, chemical, or physical reaction mechanisms for treating the fluorotelomer-based fluorosurfactants in firefighting foams and other products. The most competitive proposals, it says, will address fundamental engineering science. Trang et al. (Science, 2022) report that perfluoroalkyl carboxylic acids can be mineralized through a sodium hydroxide-mediated defluorination pathway under mild conditions: heating the acids with sodium hydroxide in mixtures of water and dimethyl sulfoxide at 80 to 120°C and ambient pressure decarboxylates them to reactive perfluoroalkyl anions (carbanions), which degraded to fluoride ions (78 to about 100%) within 24 hours. They also observed degradation of branched perfluoroalkyl ether carboxylic acids, including GenX, and write that the approach might be extended to other PFAS classes as methods to activate their polar headgroups are identified; the journal's summary of the paper notes that sulfonic acids are not currently compatible.
Entry points for student teams
A student team could build the basis of comparison to existing technologies that the NSF letter asks proposers for: a decision framework that ranks the destruction methods Trang et al. list (incineration, ultrasonication, plasma-based oxidation, electrochemical degradation, supercritical water oxidation, and ultraviolet-initiated degradation) on published preliminary data, theoretical arguments, and modeling, which needs a library rather than a laboratory. Alternatively, a team with wet-lab access could take up the letter's third priority topic — reaction mechanisms for treating the fluorotelomer-based fluorosurfactants in firefighting foams — or test whether the sodium hydroxide pathway that Trang et al. describe for perfluorocarboxylic acids extends to another PFAS class, as they suggest it might. Relevant disciplines include environmental engineering, chemistry, and materials science.
Genes
Structural cousins: stuck the same way, in other fields
Sources
NSF CBET ERASE-PFAS Dear Colleague Letter (NSF 20-090) and Environmental Engineering Program; NSF Directorate for Engineering, Division of Chemical, Bioengineering, Environmental and Transport Systems, accessed 2026-02-15 go to source ↗
Working notes
Notes made while writing and checking this brief, shown as written. They use working shorthand.
NSF's ERASE-PFAS initiative specifically identifies the "critical national need to develop effective, feasible, and sustainable remediation technologies to degrade, destroy, and/or permanently sequester PFAS." The ECO-CBET solicitation (NSF 21-596) emphasizes research topics related to curtailing climate change and mitigating its impacts; its examples mention contaminant fate and transport and organisms engineered for environmental remediation, but it does not list emerging contaminants as a priority area. Related problem in collection: water-electrochemical-arsenic-removal.md addresses a different contaminant with similar lab-to-field-gap dynamics. The sodium hydroxide defluorination pathway (Trang, Li, Xue, Ateia, Houk and Dichtel, "Low-temperature mineralization of perfluorocarboxylic acids," Science 377(6608):839–845, 2022) opened a new mechanistic avenue.
Reconciliation 2026-09-30: Fact repair after reading the whole write-up against every source it names; a second reader went over the repairs on the same day. Read in full on 2026-09-30: the NSF Dear Colleague Letter NSF 20-090 (ERASE-PFAS), fetched from the address on the Source line (the page is now marked as an archived document, publication date June 2, 2020); the NSF Environmental Engineering program description (https://www.nsf.gov/funding/opportunities/environmental-engineering/505692/pd20-1440); the ECO-CBET solicitation NSF 21-596, read both at nsf.gov (https://www.nsf.gov/funding/opportunities/eco-cbet-environmental-convergence-opportunities-chemical/505748/nsf21-596/solicitation; the older nsf.gov/pubs address no longer resolves) and from the Internet Archive copy (web.archive.org/web/20250201023057/new.nsf.gov/funding/opportunities/eco-cbet-environmental-convergence-opportunities-chemical/505748/nsf21-596/solicitation); and Trang et al. (Science, 2022), whose publisher page refuses direct fetches but whose full text was read from the Internet Archive copy of that page (web.archive.org/web/20260430094524/www.science.org/doi/10.1126/science.abm8868), with the citation record from Crossref, Europe PMC and OpenAlex (DOI 10.1126/science.abm8868). (1) The Problem Statement said PFAS are "over 14,000" chemicals that "contaminate drinking water for an estimated 200+ million Americans" and that the carbon-fluorine bond is "among the strongest in organic chemistry," making PFAS "virtually indestructible." Neither count nor superlative is in the sources. The paragraph now follows the letter: PFAS are used in firefighting foams, nonstick pans, stain-repellent fabrics, food packaging and electronics manufacturing and have contaminated soil and water; the relative inertness of the carbon-fluorine bond contributes to their persistence; and there remains a critical national need for effective, feasible and sustainable technologies to degrade, destroy or permanently sequester PFAS. The sentence that current treatment captures PFAS but cannot destroy them, concentrating them into waste streams, was removed by the first reader and restored by the second: Trang et al. write that "Adsorbents or membrane-based separation processes create PFAS-contaminated solid or liquid waste streams but do not address how to degrade these persistent pollutants." (2) Why This Matters listed the EPA's 2024 standard of 4 parts per trillion, that most US utilities will need treatment systems, and a remediation market "projected to exceed $20 billion." None of this is in the sources and it is removed. The health effects now follow Trang et al. (thyroid disease, liver damage, high cholesterol, reduced immune responses, low birth weights, several cancers) and the letter ("can lead to adverse health effects"); the paragraph also carries the letter's ask for a basis of comparison to existing technologies as evidence of sustainability and feasibility. (3) What's Been Tried described granular activated carbon and ion exchange, incineration above 1100C with hydrogen fluoride by-products, sonochemistry at milliliter scale, boron-doped diamond electrodes with fouling, supercritical water oxidation at 250+ atm, and UV/titanium dioxide photocatalysis failing on short-chain PFAS. The temperatures, pressures, scales, electrode material, catalyst and failure modes are in no source and are removed. The section now gives Trang et al.'s own account: adsorbents (activated carbon, ion-exchange resins, cross-linked polymers) and membrane separation create PFAS-contaminated waste streams without degrading the pollutants; strong carbon-fluorine bonds make PFAS resistant to end-of-life degradation; the harsh destruction methods are incineration, ultrasonication, plasma-based oxidation, electrochemical degradation, supercritical water oxidation and ultraviolet-initiated degradation with sulfite or iron additives; and current strategies are nonselective. It keeps the letter's statement that the difficulty lies in the extreme chemical stability of compounds such as PFOA and PFOS, recalcitrant to biodegradation, photo-oxidation, direct photolysis and hydrolysis. (4) What Would Unlock Progress said progress "requires" a new ambient-condition pathway (mechanochemical, plasma or biocatalytic) or an engineering breakthrough at "millions of gallons per day." The requirement, the named routes and the flow rate are not in the sources; the section now lists the letter's three priority topics and its statement that the most competitive proposals will address fundamental engineering science. The Trang finding, formerly "simple NaOH at moderate temperatures ... via a carbanion pathway," now follows the paper: sodium hydroxide in water and dimethyl sulfoxide at 80 to 120°C and ambient pressure, decarboxylation to perfluoroalkyl anions (the paper's "perfluoroalkylcarbanions"), fluoride yields of 78 to about 100% within 24 hours, degradation of branched perfluoroalkyl ether carboxylic acids including GenX, possible extension to other PFAS classes, and the journal summary's note that sulfonic acids are not currently compatible. (5) The entry points named photocatalytic methods, foam fractionation and a standardized compound set at realistic concentrations, none of which the sources mention. They now follow the letter's own ask (a basis of comparison across the destruction methods Trang et al. list, which a team can build from published data without a laboratory) and the letter's third priority topic, plus the extension Trang et al. suggest; "electrochemistry" among the disciplines became "chemistry." (6) The Source Notes said the ECO-CBET solicitation "lists emerging contaminant mitigation as a priority area." The solicitation's stated strategic challenge is combating climate change and mitigating its impacts; contaminants appear only in an illustrative example. The sentence now says that. (7) The Source Notes dated the Trang discovery to 2024 and said "subsequent NSF-funded work is exploring" it. The record gives August 19, 2022 (Science 377, issue 6608, pages 839–845), and no source mentions subsequent NSF-funded work; the year is corrected, the citation now carries the authors, title, volume, issue and pages copied from the Crossref record, and the NSF-funded-work clause is removed. Confirmed in the sources and left as written: the Source line (Dear Colleague Letter, ERASE-PFAS, NSF 20-090, Environmental Engineering program, CBET, Directorate for Engineering); the quotation "critical national need to develop effective, feasible, and sustainable remediation technologies to degrade, destroy, and/or permanently sequester PFAS," which appears word for word in the letter; the "ERASE-PFAS" name; and the related brief water-electrochemical-arsenic-removal.md, which exists in the collection. No title changed; the long title's "cost-effective" and "at water treatment scale" are a rendering of the letter's "effective, feasible, and sustainable" and "aquatic systems, and waste streams" rather than its words, and are left for Beth. Genome tags untouched.