Per- and polyfluoroalkyl substances in the environment

May combine two claims.

Transformation efficiency decreases from aerobic to anoxic to anaerobic conditions, and PFCA yields and formation rates depend on the specific precursor and transformation conditions.

“Efficiency of these transformations decreases from aerobic to anoxic to anaerobic (60, 61) conditions, and PFCA yields and rates of formation depend on specific precursor and transformation conditions (9).”

• cites [60] sourceDisputed

  The Conclusions (p. 12) report PFCA transformation yields of 11.12%, 0.46%, and 3.39% under aerobic, anoxic, and anaerobic conditions, respectively. Transformation efficiency therefore does not decrease in the stated order: anaerobic yield exceeds anoxic yield. The paper does report decreasing 8:2 FTOH biodegradation rate constants, but those are distinct from PFCA transformation yields; the sentence’s separate claim about precursor-dependent yields and rates is cited to another source. (LLM, conf=0.88)

  Checked by a reasoning model — may be wrong.

  Experimental — accuracy not yet measured
• cites [61] sourceNot checked — no full text of the source
• cites [9] sourceSupported

Probably not a substantial claim: may not pass S3 (load-bearing).

Global production volumes of fluoropolymers exceed 230,000 tonnes per year.

“With global production volumes of fluoropolymers surpassing 230,000 tonnes/year (2)”

• cites [2] sourcePartly supported

  The Discussion section (‘Scope of the present study and uncertainties’; page not provided) estimates fluoropolymer production at about 230,000 tonnes per year globally. That supports the scale and annual basis of the claim, but ‘about’ does not establish that production surpasses 230,000 tonnes. (LLM, conf=0.86)

  Experimental — accuracy not yet measured

Probably not a substantial claim: may not pass S3 (load-bearing).

PFAS have been used in more than 200 use areas because of the carbon-fluorine bond's stability and their oil- and water-repellent properties.

“PFAS have been incorporated in more than 200 use areas ranging from industrial-mining applications to food production and fire-fighting foams due to the innate chemical and thermal stability of the carbon-fluorine bond and ability to repel oil and water (2).”

• cites [2] sourceSupported

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

The 2021 OECD revised definition of PFAS is more inclusive and unambiguously includes side-chain fluorinated aromatics.

“This revised definition is more inclusive with unambiguous inclusion of PFAS such as side-chain fluorinated aromatics (Fig. 2) (11, 12).”

• cites [10]Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

• cites [11] sourceCould not verify

  The Introduction’s “Environmental Risk of Fluoro-Agrochemicals” section discusses PFAS and perfluoroalkyl chains, but does not address an OECD definition or the classification of side-chain fluorinated aromatics. Searches for the 2021 OECD revision and side-chain fluorinated aromatics found no passage supporting the attributed claim; page numbers are unavailable in our copy. (LLM, conf=0.77)

  Experimental — accuracy not yet measured
• cites [12] sourceCould not verify

  The Chemotypes of the Fluoro-Pharmaceuticals on the Market section (page unavailable) classifies fluorinated drug structures, including aryl–CF3 compounds, but does not discuss PFAS definitions. Searches for the 2021 OECD revision and side-chain fluorinated aromatics found no passage addressing whether that definition includes them. (LLM, conf=0.78)

  Experimental — accuracy not yet measured

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Major PFAS groups from direct fluorination include hydrofluorocarbons, hydrofluoroethers, hydrochlorofluoroolefins, and hydrofluoroolefins containing a -CF3 moiety, with global production over one megatonne per year.

“Major PFAS groups from direct fluorination include those hydrofluorocarbons, hydrofluoroethers, hydrochlorofluoroolefins and hydrofluoroolefins that contain a -CF3 moiety and have an overall global production of over one megatonne/year (24).”

• cites [24] sourcePartly supported

  Section 2.2 (page not available) says major commercial routes for HFCs and HFOs involve a reaction with hydrofluoric acid, and section 2.1.3.1 reports HFC production quantities. The cited paper does not identify the listed compounds as major PFAS groups from direct fluorination, address hydrofluoroethers or the -CF3 qualifier, or establish combined global production above one megatonne per year. (LLM, conf=0.82)

  Experimental — accuracy not yet measured

May combine two claims.

Functional moieties of starting materials can react further to yield different PFAS, so final products may contain unreacted intermediates and degradation products.

“Within individual PFAS groups, the functional moieties of starting materials may further react following conventional reaction pathways to yield different PFAS (9); thus, depending on the complexity of synthetic routes, final products may contain a number of unreacted intermediates and degradation products (22, 23).”

• cites [9] sourceSupported
• cites [22] sourceNot checked — no full text of the source
• cites [23] sourceNot checked — no full text of the source

May combine two claims.

Adding a -CF3 moiety can reduce biological degradation, increase biological activity, and assist membrane transport, making the parent compound longer lasting or more effective.

“Addition of the -CF3 moiety can reduce biological degradation, increase biological activity, and assist with membrane transport, making the parent compound longer lasting or more effective”

• cites [11] sourcePartly supported

  The Chemotype section says fluorinated groups can improve binding to biological targets, and the Agrochemical Type section says increased fluorine content can improve uptake across surface barriers and movement within membranes. The Environmental Risk section describes resistance to enzymatic degradation for fluoro-agrochemicals generally. These passages support the proposed effects at a broader level, but do not establish that adding a -CF3 moiety specifically produces all three effects in a parent compound; page numbers are unavailable in our copy. (LLM, conf=0.83)

  Experimental — accuracy not yet measured
• cites [12] sourcePartly supported

  “Fluoro-Pharmaceuticals in the Past Three Decades” (page not supplied) says C–F bonds often increase metabolic stability, supporting the reduced-degradation part in general. It describes effects on absorption as complex and does not establish that adding a –CF3 group assists membrane transport or increases biological activity relative to the parent compound. The potency example in “Chiral Fluoro-Pharmaceuticals” compares two fluorinated enantiomers, not a –CF3-modified compound with its parent. (LLM, conf=0.85)

  Experimental — accuracy not yet measured

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Historically, hundreds of PACF/PASF-based derivatives with various perfluorocarbon-chain lengths were produced at kilotonnes per year and used in industrial and consumer applications.

“Historically, hundreds of PACF/PASF-based derivatives with a wide range of perfluorocarbon-chain lengths were produced, on the order of kilotonnes/year (15, 29), and used for industrial and consumer applications (2).”

• cites [15] sourceNot checked — no full text of the source
• cites [29] sourceNot checked — no full text of the source
• cites [2] sourceSupported

Probably not a substantial claim: may not pass S3 (load-bearing).

Side-chain fluorinated aromatics are produced and used annually in unknown but likely considerable amounts.

“with unknown, but likely considerable amounts being produced and used annually (e.g., prozac).”

• cites [11] sourceCould not verify

  The chemotype-classification section describes fluorinated aromatic agrochemicals, but gives no annual production or use amounts. The Introduction discusses fluorinated pharmaceuticals, while the passages found for production volume do not mention Prozac or estimate quantities for side-chain fluorinated aromatics. Searches for Prozac, annual amounts, production volume, and fluoxetine did not verify the attributed claim. (LLM, conf=0.76)

  Experimental — accuracy not yet measured
• cites [12] sourcePartly supported

  The Chemotypes of the Fluoro-Pharmaceuticals on the Market section identifies 54 aryl–CF3 pharmaceuticals, supporting the presence of side-chain-fluorinated aromatics among marketed drugs. But the paper counts registered drugs, not amounts produced or used annually; searches for production quantities and Prozac did not establish that part of the claim. (LLM, conf=0.78)

  Experimental — accuracy not yet measured

May combine two claims.

Oligomerization is less aggressive and mainly yields homologous series of target compounds, as observed near fluoropolymer and perfluoropolyether manufacturing and processing sites.

“Oligomerization is less aggressive and mainly results in homologous series of target compounds (9), as have been observed near fluoropolymer (20) and perfluoropolyether (21) manufacturing and processing sites.”

• cites [9] sourcePartly supported

  The Manufacturing Processes > Telomerization section (page unavailable) describes a reaction that yields a mixture of related perfluoroalkyl iodides with progressively longer chains, supporting the homologous-series part of the citation. It does not describe oligomerization as “less aggressive” or compare its aggressiveness with another process. The observations near manufacturing sites are attached to other citations in the citing sentence, so they are not assessed against this source. (LLM, conf=0.76)

  Experimental — accuracy not yet measured
• cites [20] sourceNot checked — no full text of the source
• cites [21] sourceSupported
  Experimental — accuracy not yet measured

May combine two claims.

High concentrations of organic solvents inhibit PFOA degradation in in-situ remedial chemical-oxidation studies, suggesting that interactions of PFAS with non-PFAS co-contaminants can alter PFAS transformation.

“High concentrations of organic solvents have been shown to inhibit PFOA degradation under in-situ remedial chemical-oxidation studies, suggesting that interactions of PFAS with other non-PFAS co-contaminants can alter PFAS transformation (40).”

• cites [40] sourceSupported

May combine two claims.

Global-background PFAS ranges in surface soils are means of about 10-60 pg/g; surface soils rarely contain lower PFAS, and higher concentrations suggest local or regional sources.

“These soil concentrations have been used to define global-background PFAS ranges in surface soils (means ~10-60 pg/g), such that surface soils rarely contain lower PFAS and higher concentrations suggest local/regional sources (88).”

• cites [88] sourcePartly supported

  Table 1 (Results and discussion; page unavailable) gives global-background means of about 11–58 pg/g for the reported compounds, and Methods treats high concentrations as potentially reflecting local or regional sources. The paper does not establish that surface soils rarely have concentrations below those means; Table 1 also reports some Southern Hemisphere means below 10 pg/g. (LLM, conf=0.86)

  Experimental — accuracy not yet measured

May combine two claims.

Atmospheric residence time governs transport distance and depends on PFAS properties including volatility, reactivity, molecular weight, and vapor-particulate partitioning.

“Atmospheric residence time governs transport distance (83) and depends on a variety of PFAS properties including volatility, reactivity, molecular weight, and vapor-particulate partitioning (82, 84, 85).”

• cites [83] sourceNot checked — no full text of the source
• cites [82] sourceNot checked — no full text of the source
• cites [84] sourceSupported

May combine two claims.

In terrestrial settings, PFAS transport usually occurs via aqueous advection, with migration retarded by sorption on NOM, minerals, and fluid-fluid interfaces.

“In terrestrial settings, PFAS transport usually is via aqueous advection, with migration retarded by sorption on NOM, minerals and at fluid-fluid interfaces (particularly air-water) (91).”

• cites [91] sourcePartly supported

  The Introduction (page not available) identifies sorption to solids and adsorption at fluid-fluid interfaces as processes affecting PFAS transport; it also reports significant air-water interfacial retention in unsaturated porous media. It does not specify NOM or minerals as the sorbing solids, or state that terrestrial transport usually occurs via aqueous advection. (LLM, conf=0.86)

  Experimental — accuracy not yet measured

May combine two claims.

PFAS precursors can be metabolically converted in organisms to terminal acids or sulfonamides and can also transform during or after atmospheric or oceanic transport.

“PFAS precursors are susceptible to in-vivo metabolic conversion to terminal acids or sulfonamides post-exposure as well as transformation during (or subsequent to) atmospheric or oceanic transport (see previous sections).”

• cites [119] sourcePartly supported

  The Introduction says PFAA precursors transform both in the environment and in vivo to acids such as PFOS. Model Development describes an in-vivo pathway through sulfonamide intermediates to PFOS. The paper does not establish transformation during or after atmospheric or oceanic transport, or identify sulfonamides as terminal products. Page numbers were not available in our copy. (LLM, conf=0.87)

  Experimental — accuracy not yet measured
• cites [120] sourceNot checked yet

  Checked before — its earlier verdict is held back until a new check runs.

May combine two claims.

Waterborne rather than dietary exposure was associated with lower amphipod survival and reproduction, while higher trophic-level organisms are exposed mainly by ingestion.

“Solubilized (i.e., waterborne) rather than dietary exposure was linked to reduced amphipod survival and reproduction (133) while higher trophic-level organisms are exposed primarily through ingestion (109).”

• cites [133] sourceNot checked — no full text of the source
• cites [109] sourcePartly supported

  Citation (109) is attached to the claim about higher trophic-level organisms, not the amphipod finding. In “Approaches for quantifying exposure sources” (page unavailable), the review says dietary intake is generally the largest PFAS exposure source for human adults. It does not establish that ingestion is the primary exposure route for higher trophic-level organisms generally. (LLM, conf=0.83)

  Experimental — accuracy not yet measured

May combine two claims.

PFAS are globally persistent and are detectable in the blood of nearly all humans.

“Widespread global persistence of PFAS has resulted in detectable concentrations of the compounds in the blood of almost the entire human population (6).”

• cites [6] sourcePartly supported

  The Introduction says that widespread exposure, together with the environmental persistence and biological half-lives of some PFAS, has led to measurable PFAS in the blood of nearly the entire population in developed countries. The citing sentence extends that finding to almost the entire global population and attributes it to persistence alone; the passage does not support those extensions. No page number was supplied for the passage. (LLM, conf=0.90)

  Experimental — accuracy not yet measured

May combine two claims.

Because the carbon-fluorine bond is strong, complete PFAS mineralization is difficult, and fluorinated incomplete-destruction products are a concern.

“Given the strength of the C-F bond, complete mineralization is difficult, with fluorinated products of incomplete destruction remaining a concern (142, 143).”

• cites [142]Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

• cites [143] sourceSupported

May combine two claims.

In fauna other than terrestrial vegetation, perfluoroalkyl-acid bioaccumulation is greatest for long-chain compounds and increases with chain length.

“Conversely, potential perfluoroalkyl-acid bioaccumulation in other fauna is greatest in long-chain compounds (120), with clear trends of bioaccumulation increasing with chain length (Figs. 4C, 4F, 5) (121).”

• cites [120] sourceSupported
• cites [121] sourceNot checked — no full text of the source

May combine two claims.

PFAS-contaminated drinking water is often the main human exposure route, and water treatment methods are the most established, though removing some short-chain PFAS can be difficult and costly.

“PFAS-impacted drinking water often is the primary route of human exposure (146), and treatment techniques for aqueous media are the most well-established—although performance and cost for removal of some short-chain PFAS can be particularly challenging.”

• cites [146] sourcePartly supported

  In “Why are PFAAs in drinking water a current concern?” (page unavailable), the paper says that even low drinking-water concentrations substantially increase PFAA blood levels in exposed communities. It does not establish that drinking water is often the primary human exposure route; it also identifies diet and consumer products as exposure sources. Citation (146) is attached to the exposure-route clause, not the subsequent treatment-techniques clause. (LLM, conf=0.83)

  Experimental — accuracy not yet measured

May combine two claims.

At higher trophic levels, PFSAs such as PFOS bioaccumulate more than PFCAs such as PFOA of the same chain length and tend to be more toxic.

“At higher trophic levels, PFSAs (e.g., PFOS) bioaccumulate at greater rates than PFCAs (e.g., PFOA) of the same chain length (Fig. 5) (114, 129) and tend to be more toxic (4).”

• cites [114] sourceNot checked — no full text of the source
• cites [129] sourceNot checked — no full text of the source
• cites [4] sourceSupported

May combine two claims.

Moderate- and long-chain PFAS can cause oxidative stress and alter antioxidant defenses in invertebrates, produce neurotoxic and reprotoxic effects across species, and persist in organisms for as long as or longer than any known class of anthropogenic contaminants.

“Using these approaches, a number of moderate- and long-chain PFAS have been shown to 1) elicit varying degrees of oxidative stress and modify the antioxidant defense systems of invertebrates, 2) induce neurotoxic and reprotoxic effects across species, and 3) reside in organisms longer than or comparable to any known class of anthropogenic contaminants (120).”

• cites [120] sourcePartly supported

  Split into 2 atoms — 0 confirmed, 1 partially supported, 0 disputed, 0 misattributed, 1 unverifiable. Expand the claim to see per-atom verdicts.

  Experimental — accuracy not yet measured

May combine two claims.

In-situ stabilization can work in the short term but is not permanent and probably will not retain all PFAS species effectively.

“While this can be an effective short-term site-management technique, it is not a permanent solution, and likely will not retain all PFAS species effectively (148, 150, 151).”

• cites [148] sourceNot checked — no full text of the source
• cites [150] sourceSupported
• cites [151] sourcePartly supported

  The Abstract says stabilization can inhibit PFAS migration but does not destroy or remove PFAS. The results section (labeled “118 D” in our copy) reports substantial, but incomplete, reductions in leaching for the compounds tested. The study was limited to laboratory testing; it does not establish short-term in-situ performance, long-term permanence, or retention across all PFAS species. (LLM, conf=0.86)

  Experimental — accuracy not yet measured

May combine two claims.

In-situ modification can either increase PFAS mobility for pump-and-treat or stabilize PFAS migration using granular activated carbon or other sorbents to reduce impacts.

“Another approach to site management is in-situ modification to enhance mobility of PFAS for pump-and-treat application or to stabilize PFAS migration using GAC or other sorbents (e.g., clays) to limit impacts (150).”

• cites [150] sourcePartly supported

  Section 4.1.1 (p. 26) describes in-situ soil flushing to mobilize and extract contaminants, but does not identify pump-and-treat as the application. Section 4.2.1 describes activated carbon, including GAC, and clay-based sorbents for PFAS removal; the stabilization discussion (p. 32) reports reduced PFAS leaching with some additives. (LLM, conf=0.85)

  Experimental — accuracy not yet measured

May combine two claims.

Many destructive water-treatment technologies can destroy selected PFAS, but none have shown long-term full-scale mineralization for a wide range of PFAS in natural and industrial waters.

“Although many of these technologies have shown the ability to destroy select PFAS, none have demonstrated long-term performance approaching mineralization at full scale with natural- and industrial-water matrices for a wide assortment of PFAS.”

• cites [149] sourcePartly supported

  The Summary and Conclusion (section 5; page not provided) says some technologies achieve high destruction of parent PFAS, but none has shown complete mineralization at full scale under membrane-concentrate water qualities and treatment conditions. It does not establish the broader claim about long-term performance across natural- and industrial-water matrices and a wide assortment of PFAS. (LLM, conf=0.87)

  Experimental — accuracy not yet measured
• cites [156] sourceNot checked — no full text of the source

May combine two claims.

Incineration can at least partly destroy even highly fluorinated wastes, and advanced thermal oxidation can convert PFAS in solid, liquid, and gas samples into constituent gases with acid-scrubber cleanup.

“Incineration by itself has been shown to at least partially destroy even highly fluorinated wastes (143), and advanced thermal oxidation can be used on solid, liquid, and gas samples to convert PFAS to constituent gases with an acid-scrubber cleanup (152).”

• cites [143] sourcePartly supported

  The cited review’s “Full-scale incineration studies” section reports PFAS destruction in waste gas streams using a thermal oxidizer and four-stage scrubbing system. It does not establish that the system treats solid and liquid samples, converts PFAS specifically into constituent gases, or uses an acid scrubber. The separate incineration claim is attached to citation (143), not this source (152); page numbers are unavailable in our copy. (LLM, conf=0.85)

  Experimental — accuracy not yet measured
• cites [152]Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

Probably not a substantial claim: may not pass S3 (load-bearing).

Thousands of PFAS are present in end-use products.

“More than a megatonne is produced yearly and thousands of PFAS wind up in end-use products.”

Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

Remediation of PFAS-contaminated matrices is still in its infancy, and much current research targets drinking water.

“Efforts to remediate PFAS-contaminated matrices still are in their infancy with much current research targeting drinking water.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Estimated cumulative global emissions of perfluoroalkyl acids sum to at least 46,000 tonnes.

“estimated cumulative global emissions of perfluoroalkyl acids summing to ≥46,000 tonnes (7)”

• cites [7] sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S3 (load-bearing).

PFAS are a class of substances within organofluorine compounds.

“PFAS are a class of substances within a wide universe of organofluorine compounds (8)”

• cites [8] sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S3 (load-bearing).

PFAS have a wide range of bioaccumulation and adverse-effect concerns governed by their varied physiochemical properties.

“PFAS also have a wide range of bioaccumulation and adverse-effect concerns, governed by their varied physiochemical properties.”

Probably not a substantial claim: may not pass S3 (load-bearing).

As PFAS move through commerce from manufacturers to users to disposal, environmental release occurs through controlled and fugitive waste streams.

“As PFAS flow through commerce from primary manufacturer to commercial user to final disposal, environmental release occurs via both controlled and fugitive waste streams”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

More than 1400 individual PFAS are in the Toxic Substances Control Act Inventory, and more than 8000 unique structures are known.

“with an ever-expanding inventory of >1400 individual chemicals in the Toxic Substances Control Act Inventory and >8000 unique known structures (1)”

• cites [1]Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

Probably not a substantial claim: may not pass S3 (load-bearing).

PFAS are produced by two general synthetic routes: direct fluorination and oligomerization.

“PFAS are synthesized by two processes, direct fluorination (e.g., electrochemical) and oligomerization (e.g., fluorotelomerization).”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Some PFAS transformation pathways are well characterized, while others degrade through unknown pathways.

“Whereas some PFAS transformation pathways have been well-characterized, others degrade through yet unknown pathways”

Probably not a substantial claim: may not pass S3 (load-bearing).

Most historical research has focused on a small set of perfluoroalkyl(ether) acids and their precursors, emphasizing environmental and biological occurrence.

“In contrast, most historical work within the research community has focused on a small set of perfluoroalkyl(ether) acids and their precursors, with an emphasis on environmental and biological occurrence investigations.”

May combine two claims.

Enhanced degradation in those studies was attributed to soil organic carbon content, because adding carbon sources can increase microbial degradation rates through co-metabolic processes.

“In both studies, enhanced degradation was attributed to the organic carbon content of the soil, as addition of carbon sources can increase microbial degradation rates through co-metabolic processes (52).”

• cites [52] sourceNot checked — no full text of the source

May combine two claims.

Direct fluorination is aggressive and often causes uncontrolled reactions such as carbon-chain shortening and rearrangement, producing byproducts including cyclic and branched isomers.

“Direct fluorination is aggressive and often results in uncontrolled chemical reactions such as carbon-chain shortening and re-arrangement (17-19), leading to a wide range of byproducts including cyclic and branched isomers.”

• cites [17] sourceNot checked — no full text of the source
• cites [18] sourceNot checked — no full text of the source
• cites [19] sourceNot checked — no full text of the source

May combine two claims.

Some conditions, such as within industrial stacks, can promote PFAS partitioning to air via particulate sorption, and volatile PFAS such as FTOHs can exist in the gas phase, making atmospheric and photochemical transformation possible.

“some conditions (e.g., within industrial stacks) can promote partitioning to air via particulate sorption, and volatile PFAS such as FTOHs can exist in the gas phase (42), making atmospheric/photochemical transformation possible.”

• cites [42] sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Fluoropolymers and perfluoropolyethers are high-production polymers with fluorinated backbones; fluoropolymers are produced at hundreds of kilotonnes per year, and perfluoropolyether amounts are unknown but likely considerable.

“These are high-production polymers possessing fluorinated backbones, with fluoropolymers being produced on the scale of 100s kilotonnes/year and unknown, but likely considerable, amounts for perfluoropolyethers.”

May combine two claims.

Average PFOA yields from 8:2 FTOH were 25% in aerobic soils compared with less than 1% in anaerobic sludge.

“On average perfluorooctanoic acid (PFOA) yields from 8:2 FTOH were reported to be 25% in aerobic soils compared to <1% in anaerobic sludge (62).”

• cites [62] sourceNot checked — no full text of the source

May combine two claims.

Critical data gaps include PFAS identities, production and processing locations and quantities, and final product uses, limiting identification of environmental and human exposure.

“Critical data gaps include PFAS identities, locations/quantities of production and processing, and final uses of products, limiting the capability to identify where environmental and human exposure occur.”

Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing).

The complexity of fluoropolymers and perfluoropolyethers has not been clearly communicated with a comprehensive overview of market products.

“this complexity has not been clearly communicated with a comprehensive overview of different fluoropolymers and perfluoropolyethers on the market.”

May combine two claims.

The bioavailability and degradability of fluoropolymers and perfluoropolyethers are highly variable and complex and are generally overlooked, understudied, or unknown.

“Given their variety and complexity, their subsequent bioavailability and degradability are highly variable and complex, which is generally overlooked, understudied and/or unknown.”

May combine two claims.

Hydrofluoroethers and hydrofluoroolefins have low global-warming potentials but can degrade to persistent PFCAs such as trifluoroacetate.

“While having low global-warming potentials, hydrofluoroethers and hydrofluoroolefins can ultimately degrade to highly persistent perfluorocarboxylic acids (PFCAs) such as trifluoroacetate”

• cites [27] sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Fluorine in PFAS is mined from fluorite deposits and digested to form hydrofluoric acid.

“The fluorine in PFAS is mined from fluorite (CaF2) mineral deposits, which is digested to form hydrofluoric acid (HF) (Fig. 1).”

May combine two claims.

Fluorotelomers were historically produced at about 9 kilotonnes per year, and current amounts are unknown.

“Fluorotelomers were historically produced on the order of 9 kilotonnes/year (33), with current amounts being unknown.”

• cites [33]Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

May combine two claims.

Perfluoroalkene derivatives such as p-perfluorous nonenoxybenzene sulfonate have been produced since the 1980s, and large-scale production at kilotonnes per year recently began in China as an alternative to PFOS in firefighting and oil production.

“Perfluoroalkene derivatives such as p-perfluorous nonenoxybenzene sulfonate have been produced since the 1980s; large-scale production (on the scale of kilotonnes/year) recently was initiated in China as an alternative to perfluorooctane sulfonate (PFOS) in firefighting and oil production (35).”

• cites [35] sourceNot checked — no full text of the source

May combine two claims.

Since the early 2000s, many long-chain PACF/PASF-based derivatives have been phased out due to concern, while shorter-chain derivatives are still produced and widely used in unknown amounts.

“Since the early 2000s, numerous long-chain (fluoroalkyl carbon number ≥6) PACF/PASF-based derivatives have been - and are being - phased out due to widespread concern, whereas shorter-chain PACF/PASF-based derivatives still are being produced and widely used, although in unknown amounts (15, 29).”

• cites [15] sourceNot checked — no full text of the source
• cites [29] sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Unintentional PFAS can be an important part of human and environmental exposure and merit scrutiny.

“these unintentional PFAS can constitute an important part of human and environmental exposure, and merit scrutiny.”

May combine two claims.

In the soil-water environment, microbe-facilitated functional group biotransformation can occur aerobically or anaerobically, and some microbes carrying out these reactions have been identified.

“In the soil-water environment, microbe-facilitated functional group biotransformation can occur aerobically (43, 44) or anaerobically (45-47), and some microbes that carry out these reactions have been identified (46, 48, 49).”

• cites [43] sourceNot checked — no full text of the source
• cites [44] sourceNot checked — no full text of the source
• cites [45] sourceNot checked — no full text of the source
• cites [46] sourceNot checked — no full text of the source
• cites [47] sourceNot checked — no full text of the source

May combine two claims.

Controlled degradation studies show considerable variation in biotransformation potential and possibly different major stable perfluorinated products when extrapolating half-lives and products from laboratory to environmental conditions.

“degradation studies conducted under controlled conditions result in considerable variation in biotransformation potential and possibly different major stable perfluorinated degradation products when extrapolating half-lives and major products from laboratory to environmental conditions.”

May combine two claims.

Data suggest that complex mixtures could indirectly alter biodegradation and that one PFAS may affect the transformation rate of another, although transformation kinetics of PFAS mixtures has not been reported.

“data suggest that the presence of complex mixtures could indirectly alter biodegradation and that the presence of one PFAS may affect the transformation rate of another, although transformation kinetics of PFAS mixtures has not been reported.”

• AssumptionRests on an assumption: Environmental transformation of PFAS is mainly mediated by microbes.
• AssumptionRests on an assumption: Contaminants commonly occur as components of complex mixtures.

May combine two claims.

Long-chain PFAS preferentially adsorb to soil phases, and molecular weight can approximate relative stability among PFAS sharing common reaction centers.

“With long-chain PFAS preferentially adsorbing to soil phases, molecular weight can be used as an approximate indicator of relative stability amongst PFAS sharing common reaction centers (43).”

• cites [43] sourceNot checked — no full text of the source

May combine two claims.

In a study of soils from remote sites globally, all samples contained PFAS, with homologue ratios consistent with atmospheric transport.

“in a study of soils collected from remote sites globally, all samples contained PFAS, with homologue ratios (e.g., PFOA/perfluorononanoic acid, PFOA/PFNA) consistent with atmospheric transport (79).”

• cites [79] sourceNot checked — no full text of the source

May combine two claims.

The biodegradation half-life of N-ethyl-perfluorooctanesulfonamido-ethanol in sludge is 0.7-4.2 days, while in marine sediments it is 160 days at 4°C and 44 days at 25°C.

“biodegradation studies of N-ethyl-perfluorooctanesulfonamido-ethanol in sludge reported a half-life of 0.7-4.2 days, yet the biodegradation in marine sediments was found to proceed at much slower rates (t1/2, 4 °C = 160 days and t1/2, 25 °C = 44 days)”

• cites [66] sourceNot checked — no full text of the source

May combine two claims.

Iron and aluminum oxyhydroxides have positive surface charges below about pH 8 and can electrostatically bind anionic PFAS.

“Ferric and aluminum (oxy)hydroxides bear pH-dependent, positive surface charges below their zero-point of charge at pH~8, so these minerals can electrostatically sorb anionic PFAS.”

May combine two claims.

Comparing sorption of cationic, zwitterionic, and anionic PFAS showed concentration-dependent sorption for cationic and zwitterionic PFAS, pronounced sorption hysteresis for zwitterions, and major electrostatic and NOM sorption for cationic and zwitterionic PFAS.

“Comparing the sorption of cationic, zwitterionic and anionic PFAS showed i) concentration-dependent sorption for cationic and zwitterionic PFAS, ii) pronounced sorption hysteresis for zwitterions, and iii) major electrostatic and NOM sorption for cationic and zwitterionic PFAS (94).”

• cites [94] sourceNot checked — no full text of the source

May combine two claims.

Early precursor PFAS include volatile species such as FTOHs and sulfonamido ethanols, whose presence has been established globally.

“Early precursor PFAS include volatile species (FTOHs and sulfonamido ethanols, Fig. 3), the presence of which has been established globally (80-82).”

• cites [80] sourceNot checked — no full text of the source
• cites [81] sourceNot checked — no full text of the source
• cites [82] sourceNot checked — no full text of the source

May combine two claims.

PFAS can enter terrestrial plants through several routes, and root uptake is the most studied.

“Transport of PFAS into terrestrial plants occurs via a variety of pathways, with the most studied being uptake through roots.”

May combine two claims.

Surface-soil sorption mechanisms of two PFAS with sulfonate termini include an easily extractable fraction and less reversibly sorbed fractions formed by hydrophobic association with NOM, covalent binding to NOM-OH groups as ester linkages, and physical entrapment in NOM or minerals.

“Exploring surface-soil sorption mechanisms of two PFAS having sulfonate termini revealed an easily extractable fraction, as well as less reversibly sorbed fractions composed of i) perfluoroalkyl groups hydrophobically associating with NOM, ii) sulfonate moieties covalently binding to NOM–OH groups forming ester linkages, and iii) physical entrapment in NOM or minerals (93).”

• cites [93] sourceNot checked — no full text of the source

May combine two claims.

In those soil profiles, shorter-chain PFAS accumulate similarly to one another and more than longer-chain PFAS.

“ii) shorter chains vary little amongst each other, and iii) shorter chains exceeds that of longer.”

• cites [97] sourceNot checked — no full text of the source

May combine two claims.

Subsurface authigenic minerals are common and carry surface charges that allow electrostatic sorption.

“Authigenic minerals typically are abundant in the subsurface and these minerals possess surface charges for electrostatic sorption.”

• cites [92]Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

May combine two claims.

Organic matter in surface soils usually drops sharply within the top few centimeters, and deeper subsurface zones are dominated by mineral surfaces.

“The high NOM concentrations of surface soils typically diminish precipitously in the first several centimeters below ground surface where mineral surfaces come to dominate the vertically more-expansive subsurface realm (Fig. 4) (92).”

• cites [92]Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

May combine two claims.

Transformation rate depends on pH, temperature, and microbial population, and these factors contribute to wide variation in reported precursor half-lives.

“transformation rate is dependent on a number of other environmental factors including pH, temperature and microbial population (70), and these factors contribute to a wide variation of reported precursor half-lives.”

• cites [70] sourceNot checked — no full text of the source

May combine two claims.

Anionic PFAS log Kd values rise as pH falls, matching increased positive charge on pH-dependent oxyhydroxide mineral surfaces.

“It also was observed that log Kd for anionic PFAS increased with decreasing pH, a pattern consistent with increasing positive electrostatic charge on pH-dependent surfaces of (oxy)hydroxide minerals.”

• cites [95] sourceNot checked — no full text of the source

May combine two claims.

Terrestrial vegetation bioaccumulation factors are higher for PFCAs than PFSAs, and shorter-chain perfluoroalkyl acids bioaccumulate more than longer ones, mainly because of solubility differences.

“Bioaccumulation factors for terrestrial vegetation are greater for PFCAs than PFSAs, with shorter-chain perfluoroalkyl acids bioaccumulating to a greater degree than longer, largely driven by variation in PFAS solubility (126), followed by uptake and translocation into tissues (e.g., Fig. 4C) (100, 101).”

• cites [126] sourceNot checked — no full text of the source
• cites [100] sourceNot checked — no full text of the source
• cites [101] sourceNot checked — no full text of the source

May combine two claims.

Estimating environmental exposure is difficult because there are many functionally diverse PFAS and they occur as complex mixtures.

“Estimation of environmental exposure is hindered by the sheer number of functionally diverse PFAS and is further complicated by their presence as complex mixtures.”

May combine two claims.

In a landfill groundwater plume with travel times over 24 years, several PFCA homologues became non-detect, while PFBA, PFHxA, and PFOA showed lower downgradient-to-upgradient ratios as PFCA chain length increased.

“Given travel times exceeding 24 years for flow from the landfill to the water-supply well, several PFCA homologues fell to non-detect levels, but perfluorobutanoic acid, perfluorohexanoic acid and PFOA exhibited a pattern of lower downgradient/upgradient ratios (specifically, downgradient Well 1/upgradient Well OW1f03) with increasing PFCA chain length (Fig. 4D).”

• cites [105] sourceNot checked — no full text of the source

May combine two claims.

Biomagnification in predators depends on trophic level, food-chain length, and the ability to metabolize PFAS precursors.

“Biomagnification in predators is related to trophic level, food-chain length, and capacity to metabolize PFAS precursors (125).”

• cites [125] sourceNot checked — no full text of the source

May combine two claims.

Seabirds, marine mammals, and terrestrial species have higher magnification factors than organisms in exclusively aquatic food webs, where gilled animals eliminate perfluoroalkyl acids more efficiently.

“Seabirds, marine mammals, and terrestrial species show the greatest magnification factors compared with exclusively aquatic food webs in which organisms with gills eliminate perfluoroalkyl acids more efficiently (120).”

• cites [120] sourceNot checked yet

  Checked before — its earlier verdict is held back until a new check runs.

May combine two claims.

In aquatic food webs, long-chain PFAS concentrations tend to rise with trophic level, which is consistent with biomagnification.

“Long-chain PFAS concentrations tend to increase with trophic level in aquatic food webs, consistent with biomagnification processes (127).”

• cites [127] sourceNot checked — no full text of the source

May combine two claims.

Many current treatment technologies only concentrate PFAS, and concentrated residuals can reintroduce PFAS into the environment.

“Many existing treatment technologies are only capable of concentrating PFAS (144), and concentrated treatment residuals can result in reintroduction of PFAS into the environment (Fig 6);”

• cites [144] sourceNot checked — no full text of the source

May combine two claims.

Unexposed offspring of fish exposed to PFOA and PFOS had lower survival, reduced growth, and thyroid-related effects.

“For instance, unexposed progeny of fish exposed to PFOA and PFOS had lower survival rates, reduced growth, and thyroid-related effects as revealed by histology (138).”

• cites [138] sourceNot checked — no full text of the source

May combine two claims.

Drinking water treatment can lower human exposure at the treatment site while creating a PFAS source where residuals are produced.

“for example, treatment of drinking water can reduce human exposure at the site of treatment while also acting as a PFAS source where residuals are generated, reinforcing the need for a preventative and holistic approach (145).”

• cites [145]Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

May combine two claims.

At AFFF-contaminated sites, PFSAs were the most abundant PFAS in sediment and water, but exposed aquatic invertebrates had elevated PFCAs and 6:2 fluorotelomer sulfonate.

“For example, while PFSAs were the most abundant PFAS in both sediment and water at sites contaminated with AFFF (114), aquatic invertebrates exposed to AFFF displayed elevated concentrations of PFCAs as well as the 6:2 fluorotelomer sulfonate (114, 115).”

• cites [114] sourceNot checked — no full text of the source
• cites [115] sourceNot checked — no full text of the source

May combine two claims.

PFAS do not act like neutral hydrophobic organic contaminants and are thought to interact with both phospholipids and protein-rich tissues because they are anionic.

“PFAS do not behave like neutral, hydrophobic organic contaminants and instead are hypothesized to involve both phospholipids and proteinaceous tissues due in part to their anionic nature (123).”

• cites [123] sourceNot checked — no full text of the source

May combine two claims.

Differences in PFAS concentrations between fish and benthic invertebrates depend largely on functional group and exposure route, and high concentrations are often linked to local sources or benthic prey.

“Discrepancies in the relative concentrations of PFAS in fish compared to benthic invertebrates appear largely dependent on the compounds’ functional group and exposure routes, with elevated PFAS concentrations often linked to site-specific sources and/or benthic prey (131-133).”

• cites [131] sourceNot checked — no full text of the source
• cites [132] sourceNot checked — no full text of the source
• cites [133] sourceNot checked — no full text of the source

May combine two claims.

International reporting practices for PFAS synthesis, production volumes, and releases differ by country and are not always suited to tracking and understanding PFAS movement in the environment.

“Current international reporting practices used to document PFAS synthesis, production volumes, and potential releases vary among countries and are not always tailored to provide the knowledge necessary to adequately track and understand the movement of these compounds in the environment.”

May combine two claims.

Long-term storage of PFAS is only temporary because most PFAS do not naturally break down into non-fluorinated substances, so these sinks become delayed sources.

“Such sequestration is a temporary solution. Since most PFAS do not naturally degrade to non-fluorinated chemical species, these long-term sinks are time-delayed sources.”

• AssumptionRests on an assumption: Most PFAS do not break down naturally into non-fluorinated substances.

May combine two claims.

In many regulatory systems, PFAS information is treated as confidential business information and excluded from inventories, so continued discovery and forensic identification are needed.

“However, under regulatory frameworks around the world, information on many PFAS is protected as confidential-business information and will not be included in this inventory (16), thereby necessitating substantial continued discovery and forensic-identification efforts around the world.”

• cites [16] sourceNot checked — no full text of the source

May combine two claims.

Energy costs reduce the sustainability and appeal of many destructive PFAS technologies, and harmful byproducts such as bromate and perchlorate remain a concern.

“Also, the energy costs of many of these technologies limit their sustainability and desirability, and the formation of harmful byproducts (e.g. bromate, perchlorate) remain a concern (144).”

• cites [144] sourceNot checked — no full text of the source

May combine two claims.

Some PFAS categories, including unknown or variable composition substances, byproducts, biological materials, and polymers, may be too complex to characterize fully and pose challenges for scientific study.

“Other PFAS, such as those classified as chemical substances of unknown or variable composition, byproducts and biological materials and polymers, may be too complex to fully characterize and can challenge scientific investigation.”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Soils can be diffusely contaminated by wet or dry deposition, land application of PFAS-rich materials, use of PFAS-containing products, or uncontrolled releases from landfills or spills.

“Environmental media such as soils that can be diffusely contaminated via i) wet/dry deposition, ii) land application of PFAS-enriched materials such as biosolids, wastewater or leachate, and iii) usage of PFAS-containing products such as AFFFs and pesticides, or uncontrolled release via unlined landfills or spills (Print Fig.).”

May combine two claims.

Thermal treatment needs temperatures above 700 °C for enough time to convert PFAS into HF and non-fluorinated products, and more highly fluorinated species need more time and higher temperatures.

“However, thermal treatment requires substantial temperatures (>700 °C) for a sufficient period to convert PFAS into HF and non-fluorinated products, with more highly fluorinated species requiring more time and higher temperature (153, 154).”

• cites [153] sourceNot checked — no full text of the source
• cites [154] sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Granular activated carbon is usually reactivated and single-use resins are usually incinerated, but little is known about PFAS fate in full-scale facilities.

“GAC typically is reactivated and single-use resins typically are incinerated where little is known regarding PFAS fate in full-scale facilities.”