Perfluoroalkyl acid distribution in various plant compartments of edible crops grown in biosolids-amended soils

Occurrence and distribution of organic ultraviolet absorbents in soils and plants from a typical industrial area in South China

Organic ultraviolet absorbents (UVAs) have attracted increasing concern due to their ubiquity, bioaccumulation, and potential toxicity. However, available information on their occurrence and transfer in terrestrial environment is still extremely insufficient. In this study, we investigated twelve UVAs in the soils and five terrestrial plant species from a typical industrial area in South China, and found their total concentrations were 5.87-76.1 (median 13.1) and 17.9-269 (median 82.9) ng/g dry weight, respectively. Homosalate was dominant in soils while benzophenone and octrizole were predominant in plants, likely due to their complex sources and bioaccumulation preferences. The bioaccumulation factors (BAFs) were further evaluated based on the ratios of UVA concentrations in plants and soils. The observed BAFs of UVAs were compound and species-specific, and most of them were much >1.0, indicating the chemicals could be transferred from soils to plants. To the best of our knowledge, this is the first report of organic UVAs in field soil-plant systems, providing information that may improve our understanding of the bioaccumulability of these chemicals in terrestrial environment and the associated risks. More studies are needed to investigate the transfer and bioaccumulation of such chemicals in soils and terrestrial biota.

Ecological risk assessment for perfluorohexanesulfonic acid (PFHxS) in soil using species sensitivity distribution (SSD) approach

Perfluorohexanesulfonic acid (PFHxS) is one of the persistent organic pollutants that has been recommended to be listed in Annex A of the Stockholm Convention. It has gained increasing attention in recent years due to its toxic effects. The guideline values of PFHxS are commonly associated with PFOS in various countries and regulatory agencies. In this study, multispecies bioassays were conducted to determine the ecological toxic effects of PFHxS, including plants, soil invertebrates, and soil microorganisms, which indicated the EC10/NOEC values ranged from 2.9 to 250 mg/kg. Where possible, logistic models were used to calculate the EC30 values for various endpoints. The species sensitivity distributions were employed to estimate the ecological investigation levels for PFHxS contamination in soils using toxicity results from literature and this study. The calculation using EC10/NOEC values from both literature and this study indicated a most conservative HC5 as 1.0 mg/kg (hazardous concentration for 5 % of the species being impacted). However, utilisation of EC30 values derived from this study resulted in a much higher HC5 for PFHxS in contaminated soils (13.0 mg/kg) which is at the higher end of the existing guideline values for PFOS for protecting ecological systems. The results obtained in this study can be useful in risk assessment processes to minimize any uncertainty using combined values with PFOS.

Linking microbiomes with per- and poly-fluoroalkyl substances (PFASs) in soil ecosystems: Microbial community assembly, stability, and trophic phylosymbiosis

Microbiomes are vital in promoting nutrient cycling and plant growth in soil ecosystems. However, microbiomes face adverse effects from multiple persistent pollutants, including per- and poly-fluoroalkyl substances (PFASs). PFASs threaten the fertility and health of soil ecosystems, yet the response of microbial community stability and trophic transfer efficiencies to PFASs is still poorly understood. This study explored the spatial patterns of PFASs in topsoil environments from the West Taihu Lake Basin of China and links their presence to soil microbial community stability at compositional and functional levels. Our results revealed that PFBA (13.87%), PFTrDA (11.63%), PFDoA (11.02%), PFOA (10.99%), and PFOS (10.39%) contributed the most to the spatial occurrence of PFASs. Soil properties, including salinity (14.47%), uniformity (9.68%), dissolved inorganic carbon (8.62%), and clay content (8.18%), affected PFASs distribution the most. In soil microbiomes, eukaryotic taxa had wider niche breadths and stronger community stability than prokaryotes when exposed to PFASs (p < 0.05). The presence of PFBA and PFHpA inhibited the functional stability of archaeal and bacterial communities (p < 0.05). PFBA and PFPeA reduced the structural stability of heterotrophic bacteria and Myxobacteria, respectively (p < 0.05). Based on null modeling, PFPeA significantly regulated the assembly processes of most microbial sub-communities (p < 0.01). The trophic transferring efficiencies of autotrophic bacteria to metazoan organisms were directly stimulated by PFASs (p < 0.05), and the potential trophic transferring efficiencies of methanogenic archaea to protozoa were inhibited by PFASs (p < 0.05). This study highlighted the potential contributions of PFASs to soil microbial community stability and food webs during ecological soil management.

Health-related toxicity of emerging per- and polyfluoroalkyl substances: Comparison to legacy PFOS and PFOA

Per- and polyfluoroalkyl substances (PFAS) are highly persistent, manufactured chemicals used in various manufacturing processes and found in numerous commercial products. With over 9000 compounds belonging to this chemical class, there is increasing concern regarding human exposure to these compounds due to their persistent, bioaccumulative, and toxic nature. Human exposure to PFAS may occur from a variety of exposure sources, including, air, food, indoor dust, soil, water, from the transfer of PFAS from non-stick wrappers to food, use of cosmetics, and other personal care products. This critical review presents recent research on the health-related impacts of PFAS exposure, highlighting compounds other than Perfluorooctanoic acid (PFOA) and Perfluoroctane sulfonate (PFOS) that cause adverse health effects, updates the current state of knowledge on PFAS toxicity, and, where possible, elucidates cause-and-effect relationships. Recent reviews identified that exposure to PFAS was associated with adverse health impacts on female and male fertility, metabolism in pregnancy, endocrine function including pancreatic dysfunction and risk of developing Type 2 diabetes, lipid metabolism and risk of childhood adiposity, hepatic and renal function, immune function, cardiovascular health (atherosclerosis), bone health including risk for dental cavities, osteoporosis, and vitamin D deficiency, neurological function, and risk of developing breast cancer. However, while cause-and-effect relationships for many of these outcomes were not able to be clearly elucidated, it was identified that 1) the evidence derived from both animal models and humans suggested that PFAS may exert harmful impacts on both animals and humans, however extrapolating data from animal to human studies was complicated due to differences in exposure/elimination kinetics, 2) PFAS precursor kinetics and toxicity mechanism data are still limited despite ongoing exposures, and 3) studies in humans, which provide contrasting results require further investigation of the long-term-exposed population to better evaluate the biological toxicity of chronic exposure to PFAS.

A review of recent studies on toxicity, sequestration, and degradation of per- and polyfluoroalkyl substances (PFAS)

The fate, effects, and treatment of per- and polyfluoroalkyl substances (PFAS), an anthropogenic class of chemicals used in industrial and commercial production, are topics of great interest in recent research and news cycles. This interest stems from the ubiquity of PFAS in the global environment as well as their significant toxicological effects in humans and wildlife. Research on toxicity, sequestration, removal, and degradation of PFAS has grown rapidly, leading to a flood of valuable knowledge that can get swamped out in the perpetual rise in the number of publications. Selected papers from the Journal of Hazardous Materials between January 2018 and May 2022 on the toxicity, sequestration, and degradation of PFAS are reviewed in this article and made available as open-access publications for one year, in order to facilitate the distribution of critical knowledge surrounding PFAS. This review discusses routes of toxicity as observed in mammalian and cellular models, and the observed human health effects in exposed communities. Studies that evaluate of toxicity through in-silico approaches are highlighted in this paper. Removal of PFAS through modified carbon sorbents, nanoparticles, and anion exchange materials are discussed while comparing treatment efficiencies for different classes of PFAS. Finally, various biotic and abiotic degradation techniques, and the pathways and mechanisms involved are reviewed to provide a better understanding on the removal efficiencies and cost effectiveness of existing treatment strategies.

Developmental exposure to real-life environmental chemical mixture programs a testicular dysgenesis syndrome-like phenotype in prepubertal lambs

Current declines in male reproductive health may, in part, be driven by anthropogenic environmental chemical (EC) exposure. Using a biosolids treated pasture (BTP) sheep model, this study examined the effects of gestational exposure to a translationally relevant EC mixture. Testes of 8-week-old ram lambs from mothers exposed to BTP during pregnancy contained fewer germ cells and had a greater proportion of Sertoli-cell-only seminiferous tubules. This concurs with previous published data from fetuses and neonatal lambs from mothers exposed to BTP. Comparison between the testicular transcriptome of biosolids lambs and human testicular dysgenesis syndrome (TDS) patients indicated common changes in genes involved in apoptotic and mTOR signalling. Gene expression data and immunohistochemistry indicated increased HIF1α activation and nuclear localisation in Leydig cells of BTP exposed animals. As HIF1α is reported to disrupt testosterone synthesis, these results provide a potential mechanism for the pathogenesis of this testicular phenotype, and TDS in humans.

Recent progress and challenges on the removal of per- and poly-fluoroalkyl substances (PFAS) from contaminated soil and water

Currently, due to an increase in urbanization and industrialization around the world, a large volume of per- and poly-fluoroalkyl substances (PFAS) containing materials such as aqueous film-forming foam (AFFF), protective coatings, landfill leachates, and wastewater are produced. Most of the polluted wastewaters are left untreated and discharged into the environment, which causes high environmental risks, a threat to human beings, and hampered socioeconomic growth. Developing sustainable alternatives for removing PFAS from contaminated soil and water has attracted more attention from policymakers and scientists worldwide under various conditions. This paper reviews the recent emerging technologies for the degradation or sorption of PFAS to treat contaminated soil and water. It highlights the mechanisms involved in removing these persistent contaminants at a molecular level. Recent advances in developing nanostructured and advanced reduction remediation materials, challenges, and perspectives in the future are also discussed. Among the variety of nanomaterials, modified nano-sized iron oxides are the best sorbents materials due to their specific surface area and photogenerated holes and appear extremely promising in the remediation of PFAS from contaminated soil and water.

Dietary Perfluorohexanoic Acid (PFHxA) Exposures in Juvenile Zebrafish Produce Subtle Behavioral Effects across Generations

Ubiquitous anthropogenic contaminants of concern, per- and polyfluoroalkyl substances (PFAS) are frequently detected in the environment and human populations around the world. Diet is a predominate route of human exposure, and PFAS are frequently measured in food. Manufacturing trends have shifted from legacy PFAS to shorter-chain alternatives that are suggested to be safer, such as perfluorohexanoic acid (PFHxA). However, the current amount of data to support safety assessments of these alternatives is not yet sufficient. The present study investigated the effects of a 42-day dietary exposure to 1, 10, or 100 ng/g PFHxA in juvenile zebrafish. The zebrafish model was leveraged to interrogate morphometrics, fecundity, and numerous behavior endpoints across multiple generations. Dietary PFHxA exposure did not result in measurable body burden and did not affect growth, fecundity, adult social perception behavior, or associative learning. PFHxA exposure did induce abnormal adult anxiety behaviors in the F0 generation that persisted transgenerationally in the F1 and F2. Abnormal larval and juvenile behavior was observed in the F1 generation, but not in the F2. PFHxA juvenile dietary exposure induced subtle and multigenerational behavior effects that warrant further investigation of this and other alternative short-chain PFAS.

Transformation and fate of pharmaceuticals, personal care products, and per- and polyfluoroalkyl substances during aerobic digestion of anaerobically digested sludge

Post-anaerobic aerobic digestion (PAAD) is a promising strategy to further reduce the volume and improve the quality of anaerobically digested sludge (ADS). However, the effect of PAAD process on the fate of pharmaceuticals and personal care products (PPCPs) and per- and polyfluoroalkyl substances (PFAS) remains largely unknown. In this study, fourteen PPCPs and fifteen PFAS were detected in ADS and evaluated regarding their fate and transformation in a laboratory aerobic digester operated with a hydraulic retention time of 13 days under 22 ℃. Twelve PPCPs demonstrated significant (p < 0.05) decrease in their total concentrations (dissolved and adsorbed fractions combined) with six compounds presenting substantial transformation (> 80%) after aerobic digestion. On the contrary, PFAS were not removed and their concentrations were either increased (increasing ratio: 91 - 571%) or consistent in the sludge during PAAD process, suggesting their recalcitrance to post aerobic digestion. More than half of PPCPs and PFAS demonstrated medium to strong sorption onto solids with their solid fraction higher than 50% in the ADS. After PAAD process, sorption of four PPCPs and three PFAAs to solids was enhanced in sludge.

Assessment of Bioactive Surfactant Levels in Selected Cereal Products

Per- and polyfluoroalkyl substances (PFASs) are bioactive surfactants that are widespread in the environment and living organisms. This study presents measurements of PFAS in selected food of plant origin that are part of the healthy eating pyramid, including bread, rolls, flour, bran, buckwheat, millet, rice, and noodles. A simple and reliable analytical method was developed for the simultaneous determination of seven perfluorocarboxylic acids (PFCAs) and three perfluoroalkane sulfonates (PFSAs) in cereal-based products. Out of the 10 PFASs, 5 PFASs were detected at levels above LOQ. The most frequently detected compound was perfluorooctanoic acid (PFOA), which was quantified in 65.2% of samples, while none of the others were present in more than 40.0% of tested products. Perfluorobutanoic acid (PFBA) was the predominant PFAS in cereal-based products, and its maximum measured concentration was 202.85 ng/g for wheat bran. The soil–root–shoot interactions in relation to PFAS transfer to the above-ground parts of plants and PFAS’s ability to interfere with proteins are most likely the sources of these compounds in commonly consumed cereal products. As PFBA contributes greatly to total PFAS concentration, this food group should be included in future dietary exposure assessments.

Application of native plants in constructed floating wetlands as a passive remediation approach for PFAS-impacted surface water

Strategies for remediation of per- and polyfluoroalkyl substances (PFAS) generally prioritise highly contaminated source areas. However, the mobility of PFAS in the environment often results in extensive low-level contamination of surface waters across broad areas. Constructed Floating Wetlands (CFWs) promote the growth of plants in buoyant structures where pollutants are assimilated into plant biomass. This study examined the hydroponic growth of Juncus krausii, Baumea articulata and Phragmites australis over a 28-day period for remediation of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) contaminated (0.2 µg/L to 30 µg/L) urban stormwater. With increasing PFOA and PFOS concentrations, accumulation in plant species increased although root and shoot distribution varied depending on PFAS functional group. Less PFOA than PFOS accumulated in plant roots (0.006-0.16 versus 0.008-0.68 µg/g), while more PFOA accumulated in the plant shoots (0.02-0.55 versus 0.01-0.16 µg/g) indicating translocation to upper plant portions. Phragmites australis accumulated the highest overall plant tissue concentrations of PFOA and PFOS. The NanoSIMS data demonstrated that PFAS associated with roots and shoots was absorbed and not just surface bound. These results illustrate that CFWs have the potential to be used to reduce PFAS contaminants in surface waters.

Emerged macrophytes to the rescue: Perfluoroalkyl acid removal from wastewater and spiked solutions

This study evaluated the potential for three emergent aquatic macrophytes to remove perfluoroalkyl acids (PFAAs) from contaminated waters in constructed wetland systems. Three plants (Iris pseudacorus L., Phragmites australis (Cav.) Trin. Ex Steud., and Typha latifolia L.) were exposed to an effluent from a tannery wastewater treatment plant (WWTP) that contained residual PFAAs, and to three spiked solutions with increasing concentrations of 11 perfluorocarboxylic acids (PFCAs) and three perfluorosulfonic acids (PFSAs) (500, 2500, and 5000 ng L^-1, each). Thirty-six lightweight expanded clay aggregate- and vegetation-filled tanks (0.35 × 0.56 × 0.31 m) were exposed to the tested solutions at the Acque del Chiampo SpA WWTP in Arzignano (NE Italy). Throughout the experiment, PFAA concentrations and physicochemical water parameters were monitored via measures of the clay material, plastic tank inner surfaces, and below- and above-ground biomasses (after harvest). Vegetation growth was shown to be unaffected by increased PFAA levels in the spiked solutions. Alternatively, total biomass was significantly reduced when WWTP water was used, although we attribute this finding to the relatively high salinity that mainly restricted Typha and Iris development. The tested macrophytes were found to remove a significant PFAA mass from the contaminated waters (36% to ca. 80%, on average) when Phragmites was subjected to the highest PFAA concentrations. Such large accumulations were primarily associated with long C-chain PFAA stabilization in belowground biomass (26%, on average). Most PFAA translocations were observed in Typha, which accumulated mostly short perfluorinated C-chain PFBA, PFPeA, and PFHxA in the aboveground biomass (16%, on average). Despite some growth limitations, Iris was still the most efficient macrophyte for translocating PFBS under WWTP.

Translocation, bioaccumulation, and distribution of perfluoroalkyl and polyfluoroalkyl substances (PFASs) in plants

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are persistent in the environment and have been detected in a variety of plants such as vegetables, cereals, and fruits. Increasing evidence shows that plants are at a risk of being adversely affected by PFASs. This review concludes that PFASs are predominantly absorbed by roots from sources in the soil; besides, the review also discusses several factors such as soil properties and the species of PFASs and plants. In addition, following uptake by root, long-chain PFASs (C ≥ 7 for PFCA and C ≥ 6 for PFSA) were preferentially retained within the root, whereas the short-chain PFASs were distributed across tissues above the ground — according to the studies. The bioaccumulation potential of PFASs within various plant structures are further expressed by calculating bioaccumulation factor (BAF) across various plant species. The results show that PFASs have a wide range of BAF values within root tissue, followed by straw, and then grain. Furthermore, owing to its high water solubility than other PFASs, PFOA is the predominant compound accumulated in both the soil itself and within the plant tissues. Among different plant groups, the potential BAF values rank from highest to lowest as follows: leaf vegetables > root vegetables > flower vegetables > shoot vegetables. Several PFAS groups such as PFOA, PFBA, and PFOS, may have an increased public health risk based on the daily intake rate (ID). Finally, future research is suggested on the possible PFASs degradation occurring in plant tissues and the explanations at genetic-level for the metabolite changes that occur under PFASs stress.

•

Long-chain PFASs are preferentially retained in the roots

•

BAF values were ranked as root > straw > grain in one plant

•

PFOA is the main compound in soil and within plant tissues

•

PFOA, PFBA, and PFOS have a potential risk to humans through dietary exposure

Distribution, sources, and dietetic-related health risk assessment of perfluoroalkyl acids (PFAAs) in the agricultural environment of an industrial-agricultural interaction region (IAIR), Changshu, East China

The exploration of the distribution and dietetic-related health risks of perfluoroalkyl acids (PFAAs) in industrial-agricultural interaction regions (IAIRs) is of significant importance, due to the transfer of many PFAA-related factories to developing countries with intensive agricultural activities. In the present study, based on the local diet, edible parts of rice, vegetables, fish, and their corresponding soils and irrigation/aquaculture water were investigated in a typical Chinese city (Changshu). The concentrations of total perfluoroalkyl acids (ΣPFAAs) in the edible parts of rice /vegetables and fish tissues ranged from 26.69 to 37.09 ng/g dw, 12.93 to 40.77 ng/g dw, and 13.27 to 29.82 ng/g ww, with perfluorohexanoic acid (PFPeA) and perfluorooctane sulfonic acid (PFOS) as the most dominant compounds. The PFAA concentrations in the corresponding rice soils, vegetable soils, irrigation water, and aquaculture water ranged from 11.99 to 26.33 ng/g dw, 14.06 to 36.19 ng/g dw, 141.36 to 297.00 ng/L, and 179.23 to 235.82 ng/L, respectively. Biota-sediment accumulation factor (BSAF) values for the plant-soil system were far greater than those for bioaccumulation factor (BAF) values for the plant-irrigation water system. PFAAs were more inclined to accumulate in the gills of fish as determined by their highest BAF values. Correlation analysis showed that PFAAs in root vegetables had a stronger correlation with those in soil compared with those in irrigation water. Source analysis showed that emissions from fluoride industries, textiles, and food industries may be the dominant sources of PFAAs in agricultural environments. The estimated dietary intake (EDI) for the selected diet was lower than that for rice/vegetables but was higher than that found in fish. Toddlers (2-5 years) had the highest exposure risk, and rural residents were more exposed to PFAAs than urban residents under the selected diet.

Bioaccumulation and biotransformation of tetrabromoethylcyclohexane (TBECH) in maize (Zea mays L.): Stereoselective driving roles of plant biomacromolecules

The bioaccumulation and biotransformation of tetrabromoethylcyclohexane (TBECH) in maize were investigated. Furthermore, the roles of plant biomacromolecules such as lipid transfer proteins (LTPs), CYP and GST enzymes in driving the biological processes of TBECH stereoisomers were explored. The uptake and translocation of TBECH in maize were diastereo- and enantio-selective. Isomerization from α- to δ-TBECH and β- to γ-TBECH, and metabolites of debromination, hydroxylation and TBECH-GSH adducts were identified in maize roots. The gene expressions of LTPs, CYPs and GSTs were extensively changed in maize after exposure to technical TBECH. CYP and GST enzyme activities as well as GST31 and CYP71C3v2 gene expressions were selectively induced or inhibited by TBECH diastereomers over time. TBECH was able to dock into the active sites and bind with specific residues of the typical biomacromolecules ZmLTP1.6, GST31 and CYP71C3v2, indicating their roles in the bioaccumulation and metabolization of TBECH. Binding modes and affinities to biomacromolecules were significantly different between α- and β-TBECH, which contributed to their stereo-selectivity. This study provided a deep understanding of the biological fate of TBECH, and revealed the driving molecular mechanisms of the selectivity of TBECH stereoisomers in plants.

Source apportionment and crop bioaccumulation of perfluoroalkyl acids and novel alternatives in an industrial-intensive region with fluorochemical production, China: Health implications for human exposure

Due to their great environmental hazards, the widely used legacy perfluoroalkyl acids (PFAAs) are gradually restricted, and novel alternatives are being developed and applied. For efficient control of emerging environmental risks in agricultural production, we systematically studied the source apportionment in field soils and bioaccumulation characteristics in multiple crops of 12 PFAAs and five novel alternatives in an industrial-intensive region of China, followed by human exposure estimation and health risk assessment. Compared with perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), shorter-chained PFAAs and novel alternatives have become the dominant components in local soils and crops, indicating their wide application. A positive matrix factorization (PMF) model coupled with multivariate analysis identified fluoropolymer manufacturing and textile treatment as the principal sources. The bioaccumulation factors (BAFs) of individual PFAAs and alternatives in crops decreased with increasing carbon chain lengths. As a novel alternative of PFOA, hexafluoropropylene oxide dimer acid (GenX) exhibited much higher BAFs; for the alternative of PFOS, 6:2 chlorinated polyfluorinated ether sulfonic acid (6:2 Cl-PFESA) showed lower BAFs. The bioaccumulation capacities of PFAAs and alternatives were also associated with soil organic matter and crop species. Through crop consumption, short-chained PFAAs and novel alternatives might pose emerging human health threats.

Per- and polyfluoroalkyl substances in the environment

Over the past several years, the term PFAS (per- and polyfluoroalkyl substances) has grown to be emblematic of environmental contamination, garnering public, scientific, and regulatory concern. PFAS are synthesized by two processes, direct fluorination (e.g., electrochemical fluorination) and oligomerization (e.g., fluorotelomerization). More than a megatonne of PFAS is produced yearly, and thousands of PFAS wind up in end-use products. Atmospheric and aqueous fugitive releases during manufacturing, use, and disposal have resulted in the global distribution of these compounds. Volatile PFAS facilitate long-range transport, commonly followed by complex transformation schemes to recalcitrant terminal PFAS, which do not degrade under environmental conditions and thus migrate through the environment and accumulate in biota through multiple pathways. Efforts to remediate PFAS-contaminated matrices still are in their infancy, with much current research targeting drinking water.

Perfluorooctanoic Acid Transport in Soil and Absorption and Distribution in Alfalfa (Medicago sativa)

ABSTRACT

Perfluorooctanoic acid (PFOA) is used as a surfactant in consumer and industrial products and is frequently found in biosolids from wastewater treatment plants. When present in biosolids applied to croplands, PFOA can contaminate feed and fodder used by livestock, but the extent of PFOA transfer from soil to plants is not well characterized. A single dose of radiocarbon (14C)-tagged PFOA was applied to unplanted soil or soil containing growing alfalfa. PFOA transport through unplanted soil and uptake by alfalfa was monitored over a 10-week study period. Radiocarbon was initially measured in roots, stems, and leaves 7 days after [14C]-PFOA application to soil. PFOA accumulation was greatest in leaves during the 10-week sampling. By week 10, PFOA migration through unplanted soil had reached a depth of 22.8 ± 2.5 cm. In contrast, PFOA migrated to 7.5 ± 2.5 cm in soil containing alfalfa plants. The greatest predictor of PFOA concentration in alfalfa leaves was PFOA concentration in the top 5 cm of soil; PFOA concentrations at lower depths were not correlated with alfalfa PFOA concentrations. PFOA transport through soil may be slowed by the presence of forage; however, PFOA accumulation in edible portions of forage plants may increase food animal exposure to PFOA residues.

HIGHLIGHTS

Exposure routes, bioaccumulation and toxic effects of per- and polyfluoroalkyl substances (PFASs) on plants: A critical review

Per- and polyfluoroalkyl substances (PFASs) are artificial persistent organic pollutants ubiquitous in ecosystem, and their bioaccumulation and adverse outcomes in plants have attracted extensive concerns. Here, we review the toxic effects of PFASs encountered by various plants from physiological, biochemical and molecular perspectives. The exposure routes and bioaccumulation of PFASs in plants from contaminated sites are also summarized. The bioaccumulation of PFASs in plants from contaminated sites varied between ng/g and μg/g levels. The 50% inhibition concentration of PFASs for plant growth is often several orders of magnitude higher than the environmentally relevant concentrations (ERCs). ERCs of PFASs rarely lead to obvious phenotypic/physiological damages in plants, but markedly perturb some biological activities at biochemical and molecular scales. PFAS exposure induces the over-generated reactive oxygen species and further damages plant cell structure and organelle functions. A number of biochemical activities in plant cells are perturbed, such as photosynthesis, gene expression, protein synthesis, carbon and nitrogen metabolisms. To restore the desire states of cells exposed to PFASs, plants initiate several detoxifying mechanisms, including enzymatic antioxidants, non-enzymatic antioxidants, metallothionein genes and metabolic reprogramming. Future challenges and opportunities in PFAS phytotoxicity studies are also proposed in the review.

Removal of per- and poly-fluoroalkyl substances (PFASs) by wetlands: Prospects on plants, microbes and the interplay

Per- and polyfluoroalkyl substances (PFASs) represent a large family of synthetic organofluorine aliphatic compounds. They have been extensively produced since 1940s due to enormous applications as a surface-active agent, and water and oil repellent characteristics. PFASs are made to be non-biodegradable, therefore, many of them have been found in the environment albeit strict regulations have been in place since 2002. PFASs are extremely toxic compounds that can impart harm in both fauna and flora. Recent investigations have shown that wetlands might be useful for their removal from the environment as a passive and nature-based solution. To this end, understanding the role of plants, microbes, and their combined plant-microbe interplay is crucial because it could help design a sophisticated passive treatment wetland system. This review focuses on how these components (plants, microbe, substrate) can influence PFASs removal in wetlands under natural and controlled conditions. The information on underlying removal mechanisms is mostly retrieved from laboratory-based studies; however, pilot- and field-scale data are also presented to provide insights on their real-time performance. Briefly, a traditional wetland system works on the principles of phytouptake, bioaccumulation, and sorption, which are mainly due to the fact that PFASs are synthetic compounds that have very low reactivity in the environment. Nevertheless, recent investigations have also shown that Feammox process in wetlands can mineralize the PFASs; thus, opens new opportunities for PFASs degradation in terms of effective plant-microbe interplay in the wetlands. The choice of plants and bacterial species is however crucial, and the system efficiency relies on species-specific, sediment-specific and pollutant-specific principles. More research is encouraged to identify genetic elements and molecular mechanisms that can help us harness effective plant-microbe interplay in wetlands for the successful removal of PFASs from the environment.

Per- and Polyfluoroalkyl Substances (PFAS) in Integrated Crop-Livestock Systems: Environmental Exposure and Human Health Risks

Per- and polyfluoroalkyl substances (PFAS) are highly persistent synthetic organic contaminants that can cause serious human health concerns such as obesity, liver damage, kidney cancer, hypertension, immunotoxicity and other human health issues. Integrated crop–livestock systems combine agricultural crop production with milk and/or meat production and processing. Key sources of PFAS in these systems include firefighting foams near military bases, wastewater sludge and industrial discharge. Per- and polyfluoroalkyl substances regularly move from soils to nearby surface water and/or groundwater because of their high mobility and persistence. Irrigating crops or managing livestock for milk and meat production using adjacent waters can be detrimental to human health. The presence of PFAS in both groundwater and milk have been reported in dairy production states (e.g., Wisconsin and New Mexico) across the United States. Although there is a limit of 70 parts per trillion of PFAS in drinking water by the U.S. EPA, there are not yet regional screening guidelines for conducting risk assessments of livestock watering as well as the soil and plant matrix. This systematic review includes (i) the sources, impacts and challenges of PFAS in integrated crop–livestock systems, (ii) safety measures and protocols for sampling soil, water and plants for determining PFAS concentration in exposed integrated crop–livestock systems and (iii) the assessment, measurement and evaluation of human health risks related to PFAS exposure.

Per- and polyfluoroalkyl substances (PFASs) in the soil-plant system: Sorption, root uptake, and translocation

Per- and polyfluoroalkyl substances (PFASs) are ubiquitous in the environment but pose potential risks to ecosystems and human health. The soil-plant system plays an important role in the bioaccumulation of PFASs. Because most PFASs in the natural environment are anionic and amphiphilic (both lipophilic and hydrophilic), their sorption and accumulation behaviors differ from those of neutral organic and common ionic compounds. In this review, we discuss processes affecting the availability of PFASs in soil after analyzing the potential mechanisms underlying the sorption and uptake of PFASs in the soil-plant system. We also summarize the current knowledge on root uptake and translocation of PFASs in plants. We found that the root concentration factor of PFASs for plants grown in soil was not significantly correlated with hydrophobicity, whereas the translocation factor was significantly and negatively correlated with PFAS hydrophobicity regardless of whether plants were grown hydroponically or in soil. Further research on the cationic, neutral, and zwitterionic forms of diverse PFASs is urgently needed to comprehensively understand the environmental fates of PFASs in the soil-plant system. Additional research directions are suggested, including the development of more accurate models and techniques to evaluate the bioavailability of PFASs, the effects of root exudates and rhizosphere microbiota on the bioavailability and plant uptake of PFASs, and the roles of different plant organelles, lipids, and proteins in the accumulation of PFASs by plants.

Comparison of 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA) and perfluorooctane sulfonate (PFOS) accumulation and toxicity in mung bean

With the regulation of perfluorooctanesulfonate (PFOS), 6:2 chlorinated polyfluoroalkyl ether sulfonate (6:2 Cl-PFESA) has been used as a potential PFOS alternative in electroplating. In this study, the uptake, translocation and phytotoxicity of PFOS and 6:2 Cl-PFESA in mung bean (Vigna radiata (Linn.) Wilczek.) were investigated. The uptake kinetics of PFOS and 6:2 Cl-PFESA fit the Michaelis-Menten equation well, suggesting that the uptake is a carrier-mediated process. The root concentration factor (RCF) of 6:2 Cl-PFESA (34.55 mL g^-1 dw) was 1.27 times that of PFOS (27.11 mL g^-1 dw), and the translocation factor (TF) of 6:2 Cl-PFESA (0.177) was 1.07 times that of PFOS (0.165). Exposure to 6:2 Cl-PFESA and PFOS both resulted in the inhibition of mung bean seedling development. Treatment with 6:2 Cl-PFESA and PFOS led to the concentration-dependent elevation of malondialdehyde (MDA), carbonyl groups, and phosphorylated histone H2AX (γ-H2AX) levels in mung bean roots. The MDA and carbonyl group contents induced by 6:2 Cl-PFESA were 1.10-1.35 and 1.03-1.14 times, respectively, those of PFOS. The hydroxyl free radical (·OH) levels in mung bean roots after exposure to PFOS and 6:2 Cl-PFESA were elevated significantly, and the ·OH levels induced by 6:2 Cl-PFESA were higher than those induced by PFOS. Hydroxyl free radical levels were positively correlated with the MDA and carbonyl group contents in mung bean roots (p < 0.05). The dynamic changes in some antioxidative enzyme activities in mung bean seedlings were determined, including peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT). The results demonstrated the phytotoxicities of 6:2 Cl-PFESA and PFOS to mung bean in the early developmental stage. 6:2 Cl-PFESA is more harmful to mung beans than PFOS. The production of hydroxyl radical is the mechanism that causes the toxicity of PFOS and 6:2 Cl-PFESA toward plants.

Perfluoroalkylated acids (PFAAs) accumulate in field-exposed snails (Cepaea sp.) and affect their oxidative status

Perfluoroalkyl acids (PFAAs) are a group of synthetic persistent chemicals with distinctive properties, such as a high thermal and chemical stability, that make them suitable for a wide range of applications. They have been produced since the 1950s, resulting in a global contamination of the environment and wildlife. They are resistant to biodegradation and have the tendency to bio-accumulate in organisms and bio-magnify in the food chain. However, little is known about the bioaccumulation of PFAAs in terrestrial invertebrates, including how they affect the physiology and particularly oxidative status. Therefore, we studied the bioaccumulation of PFAAs in snails that were exposed for 3 and 6 weeks along a distance gradient radiating from a well-known fluorochemical hotspot (3M). In addition, we examined the potential effects of PFAAs on the oxidative status of these snails. Finally, we tested for relationships between the concentrations of PFAAs in snails with those in soil and nettles they were feeding on and the influence of soil physicochemical properties on these relationships. Our results showed higher concentrations of PFOA and/or PFOS in almost every matrix at the 3M site, but no concentration gradient along the distance gradient. The PFOS concentrations in snails were related to those in the nettles and soil, and were affected by multiple soil properties. For PFOA, we observed no relationships between soil and biota concentrations. Short-chained PFAAs were dominant in nettles, whereas in soil and snails long-chained PFAAs were dominant. We found a significant positive correlation between peroxidase, catalase and peroxiredoxins and PFAA concentrations, suggesting that snails, in terms of oxidative stress (OS) response, are possibly susceptible to PFAAs pollution. CAPSULE: We observed a positive correlation between the levels of PFAAs and the antioxidants peroxidase, catalase and peroxiredoxins in snails, exposed on nettles grown at contaminated sites.

Distribution, behaviour, bioavailability and remediation of poly- and per-fluoroalkyl substances (PFAS) in solid biowastes and biowaste-treated soil

Aqueous film-forming foam, used in firefighting, and biowastes, including biosolids, animal and poultry manures, and composts, provide a major source of poly- and perfluoroalkyl substances (PFAS) input to soil. Large amounts of biowastes are added to soil as a source of nutrients and carbon. They also are added as soil amendments to improve soil health and crop productivity. Plant uptake of PFAS through soil application of biowastes is a pathway for animal and human exposure to PFAS. The complexity of PFAS mixtures, and their chemical and thermal stability, make remediation of PFAS in both solid and aqueous matrices challenging. Remediation of PFAS in biowastes, as well as soils treated with these biowastes, can be achieved through preventing and decreasing the concentration of PFAS in biowaste sources (i.e., prevention through source control), mobilization of PFAS in contaminated soil and subsequent removal through leaching (i.e., soil washing) and plant uptake (i.e., phytoremediation), sorption of PFAS, thereby decreasing their mobility and bioavailability (i.e., immobilization), and complete removal through thermal and chemical oxidation (i.e., destruction). In this review, the distribution, bioavailability, and remediation of PFAS in soil receiving solid biowastes, which include biosolids, composts, and manure, are presented.

Phytoremediation of poly- and perfluoroalkyl substances: A review on aquatic plants, influencing factors, and phytotoxicity

Poly- and perfluoroalkyl substances (PFASs) are a group of emerging organic contaminants which are persistent to normal physicochemical treatments. The widespread use of PFASs has caused significant environmental issues. The bioaccumulation and distribution of PFASs within plant compartments have revealed great potentials for phytoremediation. In this review, the roles of aquatic plants in the process of PFASs remediation were highlighted. Moreover, there were different underlying mechanisms of PFASs uptake between terrestrial and aquatic plants. On the other hand, a wide range of influencing factors for bioaccumulation and translocation of PFASs within plant compartments are also presented and discussed. In response to exposure of PFASs, corresponding phytotoxic effects has affected the growth and metabolism of plants, which could provide beneficial guides of the phytotoxic tolerance for plant species selection in applications of phytoremediation. Finally, the discussion about whether phytoremediation is a viable option for PFASs removal and further research priorities are suggested.

Fate and budget of poly- and perfluoroalkyl substances in three common garden plants after experimental additions with contaminated river water

Poly- and perfluoroalkyl substances (PFAS) have become ubiquitous contaminants in the environment. Contamination of the terrestrial ecosystem can occur from the release of aqueous film forming foams (AFFF) used in firefighting operations. Following soil contamination with AFFF, studies report root uptake and translocation of PFAS to other plant organs, typically favouring the short chain moiety. This body of experimental work often focuses on edible organs and generally lacks entire PFAS budgets. Here, we calculate short chain (≤6 carbons) and long chain (≥6 or ≥ 7 carbons) PFAS concentrations and respective budgets for terrestrial multimedia mesocosms (plants, soil and lysimeter) of three common agricultural plants (tomato, lettuce and beet) following irrigation with low level PFAS (<1 μg L^-1) contaminated river water (short chain: 167 ng L^-1; long chain 526 ng L^-1). Total net recoveries were strong, ranging between 91% and 118% of added PFAS across all media. While soil was the largest receptor of PFAS in general (∼70% and 115%), there was considerable mobility to various media, including vegetation (∼3% and 20%) and leachate (∼1%). Translocation of short chain PFAS to tomato flowers resulted with biomagnified concentrations (maximus >4000 ng g^-1) and accounted for 1.4% of PFAS additions. While smaller tomato fruits had higher concentrations of short chain PFAS, larger fruit had more total PFAS mass. This work provides a detailed description of the fate of short and long chain PFAS when added to relatively uncontaminated terrestrial agricultural systems. We show low-level PFAS concentrations from real-world irrigation sources can affect various receptors across the multimedia landscape. This is most evident in tomato flowers and fruit where biomagnification and high total masses of short chain PFAS occurred which could have implications for pollinators and consumption, respectively.

Uptake of perfluorinated alkyl acids by crops: results from a field study

Four crops with different edible plant parts (radish, lettuce, pea and maize) were grown in outdoor lysimeters on soil spiked with 13 perfluorinated alkyl acids (PFAAs) at 4 different levels. PFAA concentrations were measured in soil, soil pore water, and different plant parts at harvest. Edible part/soil concentration factors ranged over seven orders of magnitude and decreased strongly with increasing PFAA chain length, by a factor of 10 for each additional fluorinated carbon (nCF) for pea. Three processes were responsible for most of the variability. The first was sorption to soil; calculating whole plant concentration factors on the basis of concentration in pore water instead of soil reduced the variability from five orders of magnitude to two. Second, the journey of the PFAAs with the transpiration stream to the leaves was hindered by retention in the roots driven by sorption; root retention factors increased by a factor 1.7 for each nCF. Third, transfer of PFAAs from the leaves to the fruit via the phloem flow was also hindered - presumably by sorption; fruit/leaf concentration factors decreased by a factor 2.5 for each nCF. A simple mathematical model based on the above principles described the measured concentrations in roots, leaves, fruits and radish bulbs within a factor 4 in most cases. This indicates that the great diversity in PFAA transfer from soil to crops can be largely described with simple concepts for four markedly different species.

Interactions between Lemna minor (common duckweed) and PFAS intermediates: Perfluorooctanesulfonamide (PFOSA) and 6:2 fluorotelomer sulfonate (6:2 FTSA)

Perfluorooctanesulfonamide (PFOSA) and 6:2 fluorotelomer sulfonate (FTSA) are widely present intermediates of per- and polyfluorinated substances (PFAS). Although detected at high concentrations in landfill leachate and groundwater, the interactions of these two compounds with plants have not been investigated much. In this work, uptake of these two PFAS intermediates at 10 and 200 μg/L by Lemna minor (common duckweed) were studied in detail. It was found that the biomass production of L. minor was not impacted negatively by PFOSA and FTSA at concentrations equal to or lower than 200 μg/L. Between these two target compounds, FTSA had much higher concentrations in L. minor when the concentrations and exposure times were the same as those for PFOSA. In addition, this compound at 200 μg/L inhibited the activities of catalase in L. minor significantly compared to the controls. This study indicates that PFOSA with low water solubility has low toxicity to L. minor, while FTSA at high concentration may accumulate in the floating plants and cause adverse effects on plant's antioxidative defense system. Longer-term studies of L. minor with these two and other PFAS are warranted given the important role of this floating plant in the ecosystem.

Variety-Selective Rhizospheric Activation, Uptake, and Subcellular Distribution of Perfluorooctanesulfonate (PFOS) in Lettuce (Lactuca sativa L.)

Perfluorooctanesulfonate (PFOS) as an accumulative emerging persistent organic pollutant in crops poses severe threats to human health. Lettuce varieties that accumulate a lower amount of PFOS (low-accumulating crop variety, LACV) have been identified, but the regarding mechanisms remain unsolved. Here, rhizospheric activation, uptake, translocation, and compartmentalization of PFOS in LACV were investigated in comparison with those of high-accumulating crop variety (HACV) in terms of rhizospheric forms, transporters, and subcellular distributions of PFOS. The enhanced PFOS desorption from the rhizosphere soils by dissolved organic matter from root exudates was observed with weaker effect in LACV than in HACV. PFOS root uptake was controlled by a transporter-mediated passive process in which low activities of aquaporins and rapid-type anion channels were corrected with low expression levels of PIPs (PIP1-1 and PIP2-2) and ALMTs (ALMT10 and ALMT13) genes in LACV roots. Higher PFOS proportions in root cell walls and trophoplasts caused lower root-to-shoot transport in LACV. The ability to cope with PFOS toxicity to shoot cells was poorer in LACV relative to HACV since PFOS proportions were higher in chloroplasts but lower in vacuoles. Our findings provide novel insights into PFOS accumulation in lettuce and further understanding of multiprocess mechanisms of LACV.

Occurrence, source apportionment, plant bioaccumulation and human exposure of legacy and emerging per- and polyfluoroalkyl substances in soil and plant leaves near a landfill in China

In this study, 17 legacy and emerging PFASs were investigated in soil and plant leaves near a valley-type landfill, which has been in operation for over 20 years. ΣPFASs concentrations ranged from 5.31 to 108 ng/g dw and 11.9 to 115 ng/g dw in the soil and leaf samples, respectively, and perfluorobutanoic acid (PFBA) was dominant in both soil and leaves. The concentrations of hexafluoropropylene oxide dimer acid (HFPO-DA), 6:2 chlorinated polyfluorinated ether sulfonic acid (F-53B) and 6:2 fluorotelomer sulfonic acid (6:2 FTS) were significantly higher than those of legacy PFOA and PFOS, indicating emerging alternatives were widely applied in the region. The integrated approach of PCA analysis, field investigation of relevant industrial activities in the study area, along with the Unmix model analysis quantitatively revealed that factories producing consumer products and the landfill were the major sources of PFASs in soil, accounting for 57% of total PFASs detected. Bioaccumulation factors (BAFs) of ΣPFASs in leaves varied from 0.37 to 8.59, and higher BAFs were found in camphor leaves. The log₁₀BAFs in all plant leaves showed a linear decrease with increasing carbon chain lengths for individual PFCAs (C4-C8). The BAF values of HFPO-DA, F-53B and 6:2 FTS were 0.01-3.39, 0.04-6.15 and 0.01-6.33, respectively. The human health risk assessment of EDIs showed a decreasing trend with the increasing carbon chain lengths of PFCAs (C4-C9), and the PFASs EDI indicated further study on the human health risk via vegetable consumption be warranted.

Biological and behavioral responses of European honey bee (Apis mellifera) colonies to perfluorooctane sulfonate exposure

Bees provide pollination services to managed and wild ecosystems but are threatened globally due to multiple stressors, including exposure to contaminants. Perfluorooctane sulfonate (PFOS) is a widely detected and persistent contaminant that accumulates and biomagnifies in food chains. In this exposure effect study, small whole colonies of Apis mellifera (1000 bees) were exposed to PFOS using a purpose-built cage system over a 4-week period. The PFOS exposure concentrations were provided to bees in sugar syrup at concentrations detected in the environment, ranging from 0 to 1.6 mg L^-1 . A range of biological and behavioral responses were monitored. Bee tissue, honey, and fecal matter were analyzed using isotope dilution combined with liquid chromatography-tandem mass spectrometry adapted for bee and honey matrix analysis. Bee mortality increased significantly with PFOS exposure at 0.8 mg L^-1  or greater, and brood development ceased entirely at 0.02 mg L^-1  or greater. Colony activity, temperament, hive maintenance, and defense were adversely affected in all PFOS exposure treatments compared with the control, even at the lowest PFOS exposure of 0.02 mg L^-1 . Perfluorooctane sulfonate was detected in bee tissue with a mean bioaccumulation factor of 0.3, and it was also identified in honey and in feces collected from the hive cages. These findings provide the first evidence that PFOS exposure adversely affects honey bee colonies and may transfer to honey. With PFOS contaminating thousands of sites worldwide, our study has implications for exposed bee populations under natural conditions, pollination services, the honey industry, and human health. Integr Environ Assess Manag 2021;17:673-683. © 2021 SETAC.

Sorbent assisted immobilisation of perfluoroalkyl acids in soils - effect on leaching and bioavailability

Contamination of soils and groundwater with perfluoroalkyl acids (PFAAs) is widespread due to their use in aqueous film-forming foams (AFFF). In this study the effectiveness of RemBind®, a sorbent containing activated carbon and aluminium oxyhydroxides was tested, as a tool to reduce the leaching and bioavailability of 12 PFAAs in soils, by amending contaminated soils with 5-30% (by weight) of the sorbents. Batch tests were used to determine the leaching of PFAAs. Their bioavailability to earthworms and wheat grass was assessed in greenhouse microcosms. Leaching and bioavailability of PFOS was reduced by up to 99.9%, at most sorbent application rates. Lowest reduction of leaching was found for shorter perfluoroalkyl chain length chemicals. The specific formulation of RemBind®, which is available in a basic and superior formulation, as well as the application rate were parameters for increasing effectiveness of the treatment. Furthermore, differences in leaching as well as bioavailability were seen depending on the perfluoroalkyl chain length. A preliminary assessment of the long-term stability of the treatment, assessed after a three-year curing period, suggested that the sorbent continued to be effective in reducing PFAAs in leachates, thus showing the potential of this sorbent to hinder further environmental contamination.

Review on plant uptake of PFOS and PFOA for environmental cleanup: potential and implications

Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) have gained increasing concern due to their persistent characteristics, wide distribution, biotoxicity, and bioaccumulative properties. The current remediation technologies for PFOA and PFOS are primarily focused on physical and chemical techniques. Phytoremediation has provided promising alternatives to traditional cleanup technologies due to their low operational costs, low maintenance requirements, end-use value, and aesthetic nature. In this review, uptake, translocation, and toxic effects of PFOS and PFOA are summarized and discussed. Several potential hyperaccumulators of PFOS and PFOA are provided according to the existing data. Biomass, chlorophyll, soluble protein, enzyme activities, oxidative stress, and other variables are assessed for potential indicator of PFOS/PFOA biotoxicity. The various studies on multiple scales are compared for identifying the threshold values. Several important implications and recommendations for future research are proposed at the end. This review provides an overview of current studies on plant uptake of PFOS and PFOA from the perspective of phytoremediation.

Fate and transport of per- and polyfluoroalkyl substances (PFASs) in the vadose zone

Per- and polyfluoroalkyl substances (PFASs) are a heterogeneous group of persistent organic pollutants that have been detected in various environmental compartments around the globe. Emerging research has revealed the preferential accumulation of PFASs in shallow soil horizons, particularly at sites impacted by firefighting activities, agricultural applications, and atmospheric deposition. Once in the vadose zone, PFASs can sorb to soil, accumulate at interfaces, become volatilized, be taken up in biota, or leach to the underlying aquifer. At the same time, polyfluorinated precursor species may transform into highly recalcitrant perfluoroalkyl acids, changing their chemical identity and thus transport behavior along the way. In this review, we critically discuss the current state of the knowledge and aim to interconnect the complex processes that control the fate and transport of PFASs in the vadose zone. Furthermore, we identify key challenges and future research needs. Consequently, this review may serve as an interdisciplinary guide for the risk assessment and management of PFAS-contaminated sites.

Extending the knowledge about PFAS bioaccumulation factors for agricultural plants - A review

A main source of perfluoroalkyl and polyfluoroalkyl substances (PFASs) residues in agricultural plants is their uptake from contaminated soil. Bioaccumulation factors (BAFs) can be an important tool to derive recommendations for cultivation or handling of crops prior consumption. This review compiles >4500 soil-to-plant BAFs for 45 PFASs from 24 studies involving 27 genera of agricultural crops. Grasses (Poaceae) provided most BAFs with the highest number of values for perfluorooctanoic acid and perfluorooctane sulfonic acid. Influencing factors on PFAS transfer like compound-specific properties (hydrophobicity, chain length, functional group, etc.), plant species, compartments, and other boundary conditions are critically discussed. Throughout the literature, BAFs were higher for vegetative plant compartments than for reproductive and storage organs. Decreasing BAFs per additional perfluorinated carbon were clearly apparent for aboveground parts (up to 1.16 in grains) but not always for roots (partly down to zero). Combining all BAFs per single perfluoroalkyl carboxylic acid (C4-C14) and sulfonic acid (C4-C10), median log BAFs decreased by -0.25(±0.029) and -0.24(±0.013) per fluorinated carbon, respectively. For the first time, the plant uptake of ultra-short-chain (≤ C3) perfluoroalkyl acids (PFAAs) was reviewed and showed a ubiquitous occurrence of trifluoroacetic acid in plants independent from the presence of other PFAAs. Based on identified knowledge gaps, it is suggested to focus on the uptake of precursors to PFAAs, PFAAs ≤C3, and additional emerging PFASs such as GenX or fluorinated ethers in future research. Studies regarding the uptake of PFASs by sugar cane, which accounts for about one fifth of the global crop production, are completely lacking and are also recommended. Furthermore, aqueous soil leachates should be tested as an alternative to the solvent extraction of soils as a base for BAF calculations.

Uptake and translocation of perfluoroalkyl acids with different carbon chain lengths (C2-C8) in wheat (Triticum acstivnm L.) under the effect of copper exposure

The co-contamination by perfluoroalkyl acids (PFAAs) and heavy metals (HMs) is ubiquitous in the surface environment subjected to sewage irrigation and land application of sludge. However, the joint effects of HMs and PFAAs on plant roots are not well clarified. This study explored the root uptake and acropetal translocation behaviors of C2-C8 PFAAs by wheat (Triticum acstivnm L.) under the co-exposure of copper (Cu). The underlying uptake mechanisms of PFAAs were verified in a defective root system. The results showed that excessive Cu (100-400 μmol/L) damaged the cell membrane of wheat root to increase electrolytic leakage. In the defective root system, the root concentrations of PFAAs decreased by 6%-73% and the decrease rates were negatively associated with the carbon chain length of PFAAs. Along with the decrease in root concentrations of PFAAs, the amount of ultrashort-chain (C2-C3) and short-chain (C4-C6) PFAAs translocated to the shoot also decreased by 45%-84%. In contrast, the acropetal translocation of long-chain (C8) PFAAs, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), was enhanced under Cu exposure due to the increase in root permeability as observed by increased electrolytic leakage. The shoot concentrations of PFOA and PFOS under Cu exposure were up to 5.5 and 11 times higher than those in the control, respectively. These results suggested that PFOA and PFOS could enter wheat root more easily through the breaks caused by Cu exposure and thereby their acropetal transportation to shoot was enhanced. Therefore, the risk of plant accumulation of long-chain PFAAs can be potentially underestimated if without considering the co-contamination with HMs in the environment.

Perfluorooctanoic Acid Uptake by Alfalfa (Medicago sativa) and Bioavailability in Sprague-Dawley Rats

ABSTRACT

Perfluorooctanoic acid (PFOA) is a perfluorinated alkyl substance used as a surfactant in a wide variety of industrial and consumer products. Over the past decade, concern has increased over the presence of PFOA in biosolids from wastewater treatment plants used as fertilizer on agricultural lands because of the potential for PFOA to enter the food chain. In this study, the uptake of 14C-PFOA from soil by alfalfa and 14C-PFOA bioavailability from consumption of this alfalfa was evaluated in Sprague-Dawley rats. Alfalfa leaves accumulated 14C-PFOA up to 4 to 5 μg/g of dry leaf, approximately 10 times higher than accumulation in the stem. Alfalfa was ground for feeding to 15 female Sprague-Dawley rats (175 to 200 g). Animals within metabolism cages were fed 10 g of feed (6 g of alfalfa plus 4 g of ground rat chow) twice daily for 14 days (equivalent to 50 μg of 14C-PFOA per kg per day). At the end of the feeding period, three rats were euthanized for sample collection on each of withdrawal days 0, 3, 7, 11, and 14. During the feeding and withdrawal phases, urine and feces were collected daily. At necropsy, blood, liver, kidney, adipose, muscle, skin, brain, heart, adrenal glands, spleen, lungs, and thymus were removed and assayed for 14C-PFOA by combustion and liquid scintillation counting. Rats had eliminated 72.8% ± 3.4% of the total dose via urine at 14 days, but urinary radioactivity fell below the level of detection by day 3 of the withdrawal period. Fecal elimination was 6.5% ± 1.2% of the dose and fell below the level of detection by day 2 of the withdrawal period. The rapid and high elimination via urine indicates that a majority of the dose was absorbed. The uptake of 14C-PFOA into alfalfa was low from soil with a high organic concentration; however, 14C-PFOA was highly bioavailable from the alfalfa when used as a feed component for rats. This study provides data for regulators investigating 14C-PFOA bioavailability and disposition in animals or animal products exposed to contaminated feed.

HIGHLIGHTS

The Effects of Soil Organic Carbon Content on Plant Uptake of Soil Perfluoro Alkyl Acids (PFAAs) and the Potential Regulatory Implications

Perfluoro alkyl acids (PFAAs) are known to bioconcentrate in plants grown in contaminated soils; the potential risk from consuming these plants is currently less understood. We determined that the current daily reference doses (RfDs) of the US Environmental Protection Agency (USEPA) could be met by consuming a single radish grown in soils with a perfluorooctanoic acid (PFOA) concentration of 9.7 ng/g or a perfluorooctane sulfonate (PFOS) concentration of 90.5 ng/g. Using a combination of our own research and literature data on plant uptake of PFAAs from soil, we developed equations for predicting PFAA bioconcentration factors (BCFs) for plant shoot and root tissues grown in soils with a known percentage of organic carbon. This calculated BCF was then applied to 6 scenarios with measured soil PFAA concentrations to estimate PFAA concentrations in plants and potential exposure to humans and animals consuming harvested vegetation. Five of the 6 scenarios showed potential for surpassing USEPA PFAA RfDs at soil concentrations as low as 24 ng/g PFOA and 28 ng/g PFOS. Environ Toxicol Chem 2021;40:832-845. © 2020 SETAC.

Ultrashort-chain perfluoroalkyl substance trifluoroacetate (TFA) in beer and tea - An unintended aqueous extraction

Trifluoroacetate (TFA) is an ultrashort-chain perfluoroalkyl substance, which is ubiquitously present in the aqueous environment. Due to its high mobility, it accumulates in plant material. The study presented here shows for the first time that TFA is a widely spread contaminant in beer and tea / herbal infusions. In 104beer samples from 23countries, TFA was detected up to 51 µg/L with a median concentration of 6.1 µg/L. An indicative brewing test and a correlation approach with potassium (K) indicate that the main source of TFA in beer is most likely the applied malt. It could be proven that the impact of the applied water is negligible in terms of TFA, which was supported by the analysis of numerous tap water samples from different countries. The unintended extraction of TFA was also demonstrated for tea / herbal infusions with a median concentration of 2.4 µg/L.

Removal and formation of perfluoroalkyl substances in Canadian sludge treatment systems - A mass balance approach

Poly- and per-fluoroalkyl substances (PFAS) are an emerging class of anthropogenic contaminants whose occurrence has raised concerns with the beneficial reuse of biosolids from wastewater treatment. This study evaluated the behavior of thirteen PFAS in nine Canadian sludge treatment systems including pelletization, alkaline stabilization, aerobic and anaerobic digestion processes. The composition of the overall PFAS-fluorine (ΣPFAS-F) loading in a system fed with only primary sludge was dominated by perfluorodecanoate (PFDA), whereas systems with blended primary and waste activated sludge feeds had a mix of short and long chain PFAS in raw sludges and treated biosolids. An increase in average ΣPFAS-F mass flow was observed through pelletization (19% formation) and alkaline stabilization (99% formation) processes indicating negative removal or contaminant formation. One of the two aerobic digestion systems and three of the five anaerobic digestion systems showed modest reductions (< 40% removal) in ΣPFAS-F loading. Long chain PFAS such as perfluorodecanoate (PFDA) and perfluorooctane sulfonate (PFOS) exhibited a wide variation in behavior ranging from substantial formation (> 75% formation) to modest removal (42% removal) in the surveyed systems while short chain perfluoropentanoate (PFPeA) mass flows increased through the three systems where they occurred. Overall, the contaminant mass balances revealed that there were significant changes in mass flows of the target PFAS through all kinds of sludge treatment systems. The results of this study on PFAS fate through sludge processing can inform future global PFAS risk management activities as well as sludge treatment considerations.

Aquatic plants and ecotoxicological assessment in freshwater ecosystems: a review

This paper reviews the current state-of-the-art, limitations, critical issues, and new directions in freshwater plant ecotoxicology. We selected peer-reviewed studies using relevant databases and for each (1) publication year, (2) test plant species, (3) reference plant group (microalgae, macroalgae, bryophytes, pteridophytes, flowering plants), (4) toxicant tested (heavy metal, pharmaceutical product, hydrocarbon, pesticide, surfactant, plastic), (5) experiment site (laboratory, field), and (6) toxicant exposure duration. Although aquatic plant organisms play a key role in the functioning of freshwater ecosystems, mainly linked to their primary productivity, their use as biological models in ecotoxicological tests was limited if compared to animals. Also, toxicant effects on freshwater plants were scarcely investigated and limited to studies on microalgae (80%), or only to a certain number of recurrent species (Pseudokirchneriella subcapitata, Chlorella vulgaris, Lemna minor, Myriophyllum spicatum). The most widely tested toxicants on plants were heavy metals (74%), followed by pharmaceutical products and hydrocarbons (7%), while the most commonly utilized endpoints in tests were plant growth inhibition, variations in dry or fresh weight, morpho-structural alterations, chlorosis, and/or necrosis. The main critical issues emerged from plant-based ecotoxicological tests were the narrow range of species and endpoints considered, the lack of environmental relevance, the excessively short exposure times, and the culture media potentially reacting with toxicants. Proposals to overcome these issues are discussed.

Regulating PFAS as a Chemical Class under the California Safer Consumer Products Program

BACKGROUND

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are a group of manmade chemicals containing at least one fully fluorinated carbon atom. The widespread use, large number, and diverse chemical structures of PFAS pose challenges to any sufficiently protective regulation, emissions reduction, and remediation at contaminated sites. Regulating only a subset of PFAS has led to their replacement with other members of the class with similar hazards, that is, regrettable substitutions. Regulations that focus solely on perfluoroalkyl acids (PFAAs) are ineffective, given that nearly all other PFAS can generate PFAAs in the environment.

OBJECTIVES

In this commentary, we present the rationale adopted by the State of California's Department of Toxic Substances Control (DTSC) for regulating PFAS as a class in certain consumer products.

DISCUSSION

We at the California DTSC propose regulating certain consumer products if they contain any member of the class of PFAS because: a) all PFAS, or their degradation, reaction, or metabolism products, display at least one common hazard trait according to the California Code of Regulations, namely environmental persistence; and b) certain key PFAS that are the degradation, reaction or metabolism products, or impurities of nearly all other PFAS display additional hazard traits, including toxicity; are widespread in the environment, humans, and biota; and will continue to cause adverse impacts for as long as any PFAS continue to be used. Regulating PFAS as a class is thus logical, necessary, and forward-thinking. This technical position may be helpful to other regulatory agencies in comprehensively addressing this large class of chemicals with common hazard traits. https://doi.org/10.1289/EHP7431.

Source, transportation, bioaccumulation, distribution and food risk assessment of perfluorinated alkyl substances in vegetables: A review

Contamination of perfluoroalkyl substances (PFASs) in agricultural products have attracted more and more attentions recently. In this review, relationship between PFASs and vegetables is summarized comprehensively. PFASs could transfer to cultivation soils by irrigation water, bio-amended soil, and atmospheric deposition mainly from industrial emissions. Carbon chain length of PFASs, species of vegetables and so on are key factors for PFASs migration and bioaccumulation in soils, plants and vegetables. Studies on food risk assessment of PFOA and PFOS show low consumption risk for most vegetables, however researches on other substances are lacking. In the future, we need to pay more attention on novel pollution pathway in cultivation, traceability research for considerable contamination, dietary exposure levels for different vegetables and more substances, as well as more exact and scientific food risk assessments. Additionally, effective means for PFASs adsorption in soil and removal from soil are also expected.

Different transport behaviors and mechanisms of perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS) in saturated porous media

Perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS) in soil aroused increasing concern, however there is little information about their transport in porous media, which is urgently needed to better control their environmental risks. In this study, saturated sand columns (considering the coupled effect of solution cation type and pH) and a two-site nonequilibrium transport model (TSM) were used to investigate the transport behaviors and mechanisms of PFOA and PFOS. Breakthrough data and the TSM parameters showed PFOA had higher mobility than PFOS, and divalent cation could inhibit their transport by increasing the nonequilibrium interactions between them and the sand. pH had little influence on PFOA migration when there was only monovalent cation in the solution since PFOA had limited affinity with the sand, however, polyvalent cation could provide additional adsorption sites for it through cation bridging and enhance the effect of pH. Differently, decreasing pH inhibited the transport of PFOS more significantly, and the effect was stronger than that of changing cation type. That proved mechanisms like hydrogen-bonding which were sensitive to solution pH played an important role in PFOS migration. These results provide important scientific basis to the remediation strategy and the migration prediction model development of PFOA and PFOS.

Challenges and Current Status of the Biological Treatment of PFAS-Contaminated Soils

Per- and polyfluoroalkyl substances (PFAS) are Synthetic Organic Compounds (SOCs) which are of current concern as they are linked to a myriad of adverse health effects in mammals. They can be found in drinking water, rivers, groundwater, wastewater, household dust, and soils. In this review, the current challenge and status of bioremediation of PFAs in soils was examined. While several technologies to remove PFAS from soil have been developed, including adsorption, filtration, thermal treatment, chemical oxidation/reduction and soil washing, these methods are expensive, impractical for in situ treatment, use high pressures and temperatures, with most resulting in toxic waste. Biodegradation has the potential to form the basis of a cost-effective, large scale in situ remediation strategy for PFAS removal from soils. Both fungal and bacterial strains have been isolated that are capable of degrading PFAS; however, to date, information regarding the mechanisms of degradation of PFAS is limited. Through the application of new technologies in microbial ecology, such as stable isotope probing, metagenomics, transcriptomics, and metabolomics there is the potential to examine and identify the biodegradation of PFAS, a process which will underpin the development of any robust PFAS bioremediation technology.

Remediation of poly- and perfluoroalkyl substances (PFAS) contaminated soils - To mobilize or to immobilize or to degrade?

Poly- and perfluoroalkyl substances (PFASs) are synthetic chemicals, which are introduced to the environment through anthropogenic activities. Aqueous film forming foam used in firefighting, wastewater effluent, landfill leachate, and biosolids are major sources of PFAS input to soil and groundwater. Remediation of PFAS contaminated solid and aqueous media is challenging, which is attributed to the chemical and thermal stability of PFAS and the complexity of PFAS mixtures. In this review, remediation of PFAS contaminated soils through manipulation of their bioavailability and destruction is presented. While the mobilizing amendments (e.g., surfactants) enhance the mobility and bioavailability of PFAS, the immobilizing amendments (e.g., activated carbon) decrease their bioavailability and mobility. Mobilizing amendments can be applied to facilitate the removal of PFAS though soil washing, phytoremediation, and complete destruction through thermal and chemical redox reactions. Immobilizing amendments are likely to reduce the transfer of PFAS to food chain through plant and biota (e.g., earthworm) uptake, and leaching to potable water sources. Future studies should focus on quantifying the potential leaching of the mobilized PFAS in the absence of removal by plant and biota uptake or soil washing, and regular monitoring of the long-term stability of the immobilized PFAS.

Identifying and Managing Aqueous Film-Forming Foam-Derived Per- and Polyfluoroalkyl Substances in the Environment

The use of aqueous film-forming foam (AFFF) has resulted in the widespread occurrence of per- and polyfluoroalkyl substances (PFAS) in groundwater, drinking water, soils, sediments, and receiving waters throughout the United States and other countries. We present the research and development efforts to date by the Strategic Environmental Research and Development Program (SERDP) and the Environmental Security Technology Certification Program (ESTCP) to measure PFAS in the environment, characterize AFFF-associated sources of PFAS, understand PFAS fate and behavior in the environment, assess the risk to ecological receptors, develop in situ and ex situ treatment technologies for groundwater, treat soils and investigation-derived wastes, and examine the ecotoxicity of PFAS-free fire suppression formulations. Environ Toxicol Chem 2021;40:24-36. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. This article has been contributed to by US Government employees and their work is in the public domain in the USA.

Per- and polyfluoroalkyl substances in soil and sediments: Occurrence, fate, remediation and future outlook

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are contaminants of great concern due to their wide-spread occurrence and persistence in the environments (i.e., in water, soil and sediment) and potential toxicology even at very low concentration. The main focus of this review is on the PFASs in soil and sediments. More specifically, this review systematically examines the occurrence and toxicological effects with associated risks, fate (i.e., PFASs adsorption by soil and sediment, transportation and transformation, and bioaccumulation), and remediation practices of PFASs in soil and sediment. Various models and equations such as fugacity-based multimedia fate and hydrodynamic models are used to study the fate, transport, and transformation of PFASs. Among different remediation practices, sorption is the dominant process for the removal of PFASs from soil and sediments. Results also indicate that PFASs adsorption onto activated carbon decrease with the increase of carbon chain length in the PFASs. The longer-chain PFASs have larger partition coefficient values than shorter-chained PFASs. Sorption of PFASs to soil and sediments are mainly governed by different electrostatic interactions, hydrogen bonds formation, hydrophobic interactions, organic content in soil and sediments, and ligand exchange. Other technology such as thermal treatment might be potential in the removal of PAFSs, but need further study to elucidate a conclusion. Finally, the associated challenges and future outlook have been included.