Bioaccumulation of Perfluoroalkyl Sulfonamides (FASA).

Hundreds of sites across the United States have high concentrations of perfluoroalkyl sulfonamides (FASA), but little is known about their propensity to accumulate in fish. FASA are precursors to terminal per- and polyfluoroalkyl substances (PFAS) that are abundant in diverse consumer products and aqueous film-forming foams manufactured using electrochemical fluorination (ECF AFFF). In this study, FASA with C3-C8 carbon chain lengths were detected in all fish samples from surface waters up to 8 km downstream of source zones with ECF AFFF contamination. Short-chain FASA ≤ C6 have rarely been included in routine screening for PFAS, but availability of new standards makes such analyses more feasible. Bioaccumulation factors (BAF) for FASA were between 1 and 3 orders of magnitude greater than their terminal perfluoroalkyl sulfonates. Across fish species, BAF for FASA were greater than for perfluorooctanesulfonate (PFOS), which is presently the focus of national advisory programs. Similar concentrations of the C6 FASA (<0.36-175 ng g-1) and PFOS (0.65-222 ng g-1) were detected in all fish species. No safety thresholds have been established for FASA. However, high concentrations in fish next to contaminated sites and preliminary findings on toxicity suggest an urgent need for consideration by fish advisory programs.

Global mercury concentrations in biota: their use as a basis for a global biomonitoring framework.

An important provision of the Minamata Convention on Mercury is to monitor and evaluate the effectiveness of the adopted measures and its implementation. Here, we describe for the first time currently available biotic mercury (Hg) data on a global scale to improve the understanding of global efforts to reduce the impact of Hg pollution on people and the environment. Data from the peer-reviewed literature were compiled in the Global Biotic Mercury Synthesis (GBMS) database (>550,000 data points). These data provide a foundation for establishing a biomonitoring framework needed to track Hg concentrations in biota globally. We describe Hg exposure in the taxa identified by the Minamata Convention: fish, sea turtles, birds, and marine mammals. Based on the GBMS database, Hg concentrations are presented at relevant geographic scales for continents and oceanic basins. We identify some effective regional templates for monitoring methylmercury (MeHg) availability in the environment, but overall illustrate that there is a general lack of regional biomonitoring initiatives around the world, especially in Africa, Australia, Indo-Pacific, Middle East, and South Atlantic and Pacific Oceans. Temporal trend data for Hg in biota are generally limited. Ecologically sensitive sites (where biota have above average MeHg tissue concentrations) have been identified throughout the world. Efforts to model and quantify ecosystem sensitivity locally, regionally, and globally could help establish effective and efficient biomonitoring programs. We present a framework for a global Hg biomonitoring network that includes a three-step continental and oceanic approach to integrate existing biomonitoring efforts and prioritize filling regional data gaps linked with key Hg sources. We describe a standardized approach that builds on an evidence-based evaluation to assess the Minamata Convention's progress to reduce the impact of global Hg pollution on people and the environment.

Binding of Per- and Polyfluoroalkyl Substances (PFAS) to Serum Proteins: Implications for Toxicokinetics in Humans.

Per- and polyfluoroalkyl substances (PFAS) are a diverse class of highly persistent anthropogenic chemicals that are detectable in the serum of most humans. PFAS exposure has been associated with many adverse effects on human health including immunotoxicity, increased risk of certain cancers, and metabolic disruption. PFAS binding to the most abundant blood serum proteins (human serum albumin [HSA] and globulins) is thought to affect transport to active sites, toxicity, and elimination half-lives. However, few studies have investigated the competitive binding of PFAS to these proteins in human serum. Here, we use C18 solid-phase microextraction fibers to measure HSA-water and globulin-water distribution coefficients (DHSA/w, Dglob/w) for PFAS with carbon chains containing 4 to 13 perfluorinated carbons (ηpfc = 4-13) and several functional head-groups. PFAS with ηpfc < 7 were highly bound to HSA relative to globulins, whereas PFAS with ηpfc ≥ 7 showed a greater propensity for binding to globulins. Experimentally measured DHSA/w and Dglob/w and concentrations of serum proteins successfully predicted the variability in PFAS binding in human serum. We estimated that the unbound fraction of serum PFAS varied by up to a factor of 2.5 among individuals participating in the 2017-2018 U.S. National Health and Nutrition Examination Survey. These results suggest that serum HSA and globulins are important covariates for epidemiological studies aimed at understanding the effects of PFAS exposure.

Unregulated Active and Closed Textile Mills Represent a Significant Vector of PFAS Contamination into Coastal Rivers.

Despite concerns over the ubiquity of per- and polyfluoroalkyl substances (PFAS), little is known about the diversity of input sources to surface waters and their seasonal dynamics. Frequent use of PFAS in textiles means both active and closed textile mills require evaluation as PFAS sources. We deployed passive samplers at seven sites in an urban river and estuary adjacent to textile mills in Southern Rhode Island (USA) over 12 months. We estimated monthly mass flows (g month-1) of perfluorohexanoic acid (PFHxA: 45±56), and perfluorooctanoic acid (PFOA: 30±45) from the upstream river influenced by an active mill. Average mass flows were 73-155% higher downstream, where historical textile waste lagoons contributed long chain perfluoroalkyl acids (PFAA). Mass flows of PFNA increased from 7.5 to 21 g month-1 between the upstream and downstream portions of the rivers. Distinct grouping of the two main PFAS sources, active textile mills and historical waste lagoons, were identified using principal components analysis. Neither suspect screening nor extractable organofluorine analysis revealed measurable PFAS were missing beyond the targeted compounds. This research demonstrates that both closed and active textile mills are important ongoing PFAS sources to freshwater and marine regions and should be further evaluated as a source category.

Interlaboratory Comparison of Extractable Organofluorine Measurements in Groundwater and Eel (Anguilla rostrata): Recommendations for Methods Standardization.

Research on per- and polyfluoroalkyl substances (PFAS) frequently incorporates organofluorine measurements, particularly because they could support a class-based approach to regulation. However, standardized methods for organofluorine analysis in a broad suite of matrices are currently unavailable, including a method for extractable organofluorine (EOF) measured using combustion ion chromatography (CIC). Here, we report the results of an international interlaboratory comparison. Seven laboratories representing academia, government, and the private sector measured paired EOF and PFAS concentrations in groundwater and eel (Anguilla rostrata) from a site contaminated by aqueous film-forming foam. Among all laboratories, targeted PFAS could not explain all EOF in groundwater but accounted for most EOF in eel. EOF results from all laboratories for at least one replicate extract fell within one standard deviation of the interlaboratory mean for groundwater and five out of seven laboratories for eel. PFAS spike mixture recoveries for EOF measurements in groundwater and eel were close to the criterion (±30%) for standardized targeted PFAS methods. Instrumental operation of the CIC such as replicate sample injections was a major source of measurement uncertainty. Blank contamination and incomplete inorganic fluorine removal may introduce additional uncertainties. To elucidate the presence of unknown organofluorine using paired EOF and PFAS measurements, we recommend that analysts carefully consider confounding methodological uncertainties such as differences in precision between measurements, data processing steps such as blank subtraction and replicate analyses, and the relative recoveries of PFAS and other fluorine compounds.

Sociodemographic Disparities in Mercury Exposure from United States Coal-Fired Power Plants.

Hazardous air pollutants emitted by United States (U.S) coal-fired power plants have been controlled by the Mercury and Air Toxics Standards (MATS) since 2012. Sociodemographic disparities in traditional air pollutant exposures from U.S. power plants are known to occur but have not been evaluated for mercury (Hg), a neurotoxicant that bioaccumulates in food webs. Atmospheric Hg deposition from domestic power plants decreased by 91% across the contiguous U.S. from 6.4 Mg in 2010 to 0.55 Mg in 2020. Prior to MATS, populations living within 5 km of power plants (n = 507) included greater proportions of frequent fish consumers, individuals with low annual income and less than a high school education, and limited English-proficiency households compared to the US general population. These results reinforce a lack of distributional justice in plant siting found in prior work. Significantly greater proportions of low-income individuals lived within 5 km of active facilities in 2020 (n = 277) compared to plants that retired after 2010, suggesting that socioeconomic status may have played a role in retirement. Despite large deposition declines, an end-member scenario for remaining exposures from the largest active power plants for individuals consuming self-caught fish suggests they could still exceed the U.S. Environmental Protection Agency reference dose for methylmercury.

Centurial Persistence of Forever Chemicals at Military Fire Training Sites.

Drinking water contamination by per- and polyfluoroalkyl substances (PFAS) is widespread near more than 300 United States (U.S.) military bases that used aqueous film-forming foams (AFFF) for fire training and firefighting activities. Much of the PFAS at these sites consist of precursors that can transform into terminal compounds of known health concern but are omitted from standard analytical methods. Here, we estimate the expected duration and contribution of precursor biotransformation to groundwater PFAS contamination at an AFFF-contaminated military base on Cape Cod, Massachusetts, United States, by optimizing a geochemical box model using measured PFAS concentrations from a multidecadal time series of groundwater and a soil survey in the source zone. A toolbox of analytical techniques used to reconstruct the mass budget of PFAS showed that precursors accounted for 46 ± 8% of the extractable organofluorine (a proxy for total PFAS) across years. Terminal PFAS still exceed regulatory limits by 2000-fold decades after AFFF use ceased. Measurements and numerical modeling show that sulfonamido precursors are retained in the vadose zone and their slow biotransformation into perfluoroalkyl sulfonates (half-life > 66 yr) sustains groundwater concentrations of perfluorobutane sulfonate (PFBS) and perfluorohexane sulfonate (PFHxS). The estimated PFAS reservoir in the vadose zone and modeled flux into groundwater suggest PFAS contamination above regulatory guidelines will persist for centuries without remediation.

Sociodemographic Factors Are Associated with the Abundance of PFAS Sources and Detection in U.S. Community Water Systems.

Drinking water contaminated by per- and polyfluoroalkyl substances (PFAS) is a widespread public health concern, and exposure-response relationships are known to vary across sociodemographic groups. However, research on disparities in drinking water PFAS exposures and the siting of PFAS sources in marginalized communities is limited. Here, we use monitoring data from 7873 U.S. community water systems (CWS) in 18 states to show that PFAS detection is positively associated with the number of PFAS sources and proportions of people of color who are served by these water systems. Each additional industrial facility, military fire training area, and airport in a CWS watershed was associated with a 10-108% increase in perfluorooctanoic acid and a 20-34% increase in perfluorooctane sulfonic acid in drinking water. Waste sector sources were also significantly associated with drinking water PFAS concentrations. CWS watersheds with PFAS sources served higher proportions of Hispanic/Latino and non-Hispanic Black residents compared to those without PFAS sources. CWS serving higher proportions of Hispanic/Latino and non-Hispanic Black residents had significantly increased odds of detecting several PFAS. This likely reflects disparities in the siting of PFAS contamination sources. Results of this work suggest that addressing environmental justice concerns should be a component of risk mitigation planning for areas affected by drinking water PFAS contamination.

Nitrifying Microorganisms Linked to Biotransformation of Perfluoroalkyl Sulfonamido Precursors from Legacy Aqueous Film-Forming Foams.

Drinking water supplies across the United States have been contaminated by firefighting and fire-training activities that use aqueous film-forming foams (AFFF) containing per- and polyfluoroalkyl substances (PFAS). Much of the AFFF is manufactured using electrochemical fluorination by 3M. Precursors with six perfluorinated carbons (C6) and non-fluorinated amine substituents make up approximately one-third of the PFAS in 3M AFFF. C6 precursors can be transformed through nitrification (microbial oxidation) of amine moieties into perfluorohexane sulfonate (PFHxS), a compound of regulatory concern. Here, we report biotransformation of the most abundant C6 sulfonamido precursors in 3M AFFF with available commercial standards (FHxSA, PFHxSAm, and PFHxSAmS) in microcosms representative of the groundwater/surface water boundary. Results show rapid (<1 day) biosorption to living cells by precursors but slow biotransformation into PFHxS (1-100 pM day-1). The transformation pathway includes one or two nitrification steps and is supported by the detection of key intermediates using high-resolution mass spectrometry. Increasing nitrate concentrations and total abundance of nitrifying taxa occur in parallel with precursor biotransformation. Together, these data provide multiple lines of evidence supporting microbially limited biotransformation of C6 sulfonamido precursors involving ammonia-oxidizing archaea (Nitrososphaeria) and nitrite-oxidizing bacteria (Nitrospina). Further elucidation of interrelationships between precursor biotransformation and nitrogen cycling in ecosystems would help inform site remediation efforts.

The Utility of Machine Learning Models for Predicting Chemical Contaminants in Drinking Water: Promise, Challenges, and Opportunities.

PURPOSE OF REVIEW: This review aims to better understand the utility of machine learning algorithms for predicting spatial patterns of contaminants in the United States (U.S.) drinking water. RECENT FINDINGS: We found 27 U.S. drinking water studies in the past ten years that used machine learning algorithms to predict water quality. Most studies (42%) developed random forest classification models for groundwater. Continuous models show low predictive power, suggesting that larger datasets and additional predictors are needed. Categorical/classification models for arsenic and nitrate that predict exceedances of pollution thresholds are most common in the literature because of good national scale data coverage and priority as environmental health concerns. Most groundwater data used to develop models were obtained from the United States Geological Survey (USGS) National Water Information System (NWIS). Predictors were similar across contaminants but challenges are posed by the lack of a standard methodology for imputation, pre-processing, and differing availability of data across regions. We reviewed 27 articles that focused on seven drinking water contaminants. Good performance metrics were reported for binary models that classified chemical concentrations above a threshold value by finding significant predictors. Classification models are especially useful for assisting in the design of sampling efforts by identifying high-risk areas. Only a few studies have developed continuous models and obtaining good predictive performance for such models is still challenging. Improving continuous models is important for potential future use in epidemiological studies to supplement data gaps in exposure assessments for drinking water contaminants. While significant progress has been made over the past decade, methodological advances are still needed for selecting appropriate model performance metrics and accounting for spatial autocorrelations in data. Finally, improved infrastructure for code and data sharing would spearhead more rapid advances in machine-learning models for drinking water quality.

Organic Fluorine as an Indicator of Per- and Polyfluoroalkyl Substances in Dust from Buildings with Healthier versus Conventional Materials.

Per- and polyfluoroalkyl substances (PFAS) are a class of thousands of persistent, organic fluorinated chemicals added to materials and products mainly to repel stains and water. PFAS have been associated with many adverse human health effects. We aimed to determine whether buildings with "healthier" materials─defined here as reportedly free of all PFAS─exhibit lower PFAS in dust. In addition to analyzing targeted PFAS with available commercial standards, we measured extractable organic fluorine (EOF) as a novel proxy that includes both known and unknown types of PFAS. We measured at least 15 targeted PFAS (n = 24), EOF (n = 24), and total fluorine (TF; n = 14) in dust collected from university common spaces and classrooms, half of which had "healthier" furniture and carpet. We observed lower PFAS contamination in buildings with "healthier" materials: "healthier" rooms had a 66% lower median summed PFAS and a 49% lower Kaplan-Meier estimated mean EOF level in dust in comparison to conventional rooms. The summed targeted PFAS were significantly correlated with EOF but accounted for up to only 9% of EOF, indicating the likely presence of unidentified PFAS. EOF levels explained less than 1% of TF in dust. We emphasize the need to use chemical class-based methods (e.g., EOF) for evaluating class-based solutions and to expand non-PFAS solutions for other building materials.

PFAS and Precursor Bioaccumulation in Freshwater Recreational Fish: Implications for Fish Advisories.

Per- and polyfluoroalkyl substances (PFAS) are a diverse class of fluorinated anthropogenic chemicals that include perfluoroalkyl acids (PFAA), which are widely used in modern commerce. Many products and environmental samples contain abundant precursors that can degrade into terminal PFAA associated with adverse health effects. Fish consumption is an important dietary exposure source for PFAS that bioaccumulate in food webs. However, little is known about bioaccumulation of PFAA precursors. Here, we identify and quantify PFAS in recreational fish species collected from surface waters across New Hampshire, US, using a toolbox of analytical methods. Targeted analysis of paired water and tissue samples suggests that many precursors below detection in water have a higher bioaccumulation potential than their terminal PFAA. Perfluorobutane sulfonamide (FBSA), a short-chain precursor produced by electrochemical fluorination, was detected in all fish samples analyzed for this compound. The total oxidizable precursor assay interpreted using Bayesian inference revealed fish muscle tissue contained additional, short-chain precursors in high concentration samples. Suspect screening analysis indicated these were perfluoroalkyl sulfonamide precursors with three and five perfluorinated carbons. Fish consumption advisories are primarily being developed for perfluorooctane sulfonate (PFOS), but this work reinforces the need for risk evaluations to consider additional bioaccumulative PFAS, including perfluoroalkyl sulfonamide precursors.

Elevated Mercury Concentrations and Isotope Signatures (N, C, Hg) in Yellowfin Tuna (Thunnus albacares) from the Galápagos Marine Reserve and Waters off Ecuador.

We examined how dietary factors recorded by C and N influence Hg uptake in 347 individuals of yellowfin tuna (Thunnus albacares), an important subsistence resource from the Galápagos Marine Reserve (Ecuador) and the Ecuadorian mainland coast in 2015-2016. We found no differences in total Hg (THg) measured in red muscle between the two regions and no seasonal differences, likely due to the age of the fish and slow elimination rates of Hg. Our THg concentrations are comparable to those of other studies in the Pacific (0.20-9.60 mg/kg wet wt), but a subset of individuals exhibited the highest Hg concentrations yet reported in yellowfin tuna. Mercury isotope values differed between Δ199 Hg and δ202Hg in both regions (Δ199 Hg = 2.86 ± 0.04‰ vs. Δ199 Hg = 2.33 ± 0.07‰), likely related to shifting food webs and differing photochemical processing of Hg prior to entry into the food web. There were significantly lower values of both δ15 N and δ13 C in tuna from Galápagos Marine Reserve (δ15 N: 8.5-14.2‰, δ13 C: -18.5 to -16.1‰) compared with those from the Ecuadorian mainland coast (δ15 N: 8.3-14.4‰, δ13 C: -19.4 to -11.9‰), of which δ13 C values suggest spatially constrained movements of tuna. Results from the pooled analysis, without considering region, indicated that variations in δ13 C and δ15 N values tracked changes of Hg stable isotopes. Our data indicate that the individual tuna we used were resident fish of each region and were heavily influenced by upwellings related to the eastern Pacific oxygen minimum zone and the Humboldt Current System. The isotopes C, N, and Hg reflect foraging behavior mainly on epipelagic prey in shallow waters and that food web shifts drive Hg variations between these populations of tuna. Environ Toxicol Chem 2022;41:2732-2744. © 2022 SETAC.

Study Protocol: Interactive Dynamics of Coral Reef Fisheries and the Nutrition Transition in Kiribati.

The Kiribati 2019 Integrated Household Income and Expenditure Survey (Integrated HIES) embeds novel ecological and human health research into an ongoing social and economic survey infrastructure implemented by the Pacific Community in partnership with national governments. This study seeks to describe the health status of a large, nationally representative sample of a geographically and socially diverse I-Kiribati population through multiple clinical measurements and detailed socio-economic surveys, while also conducting supporting food systems research on ecological, social, and institutional drivers of change. The specific hypotheses within this research relate to access to seafood and the potential nutritional and health benefits of these foods. We conducted this research in 21 of the 23 inhabited islands of Kiribati, excluding the two inhabited islands-Kanton Islands in the Phoenix Islands group with a population of 41 persons (2020 census) and Banaba Island in the Gilbert Islands group with a population of 333 persons (2020 census)-and focusing exclusively on the remaining islands in the Gilbert and Line Islands groups. Within this sample, we focused our intensive human health and ecological research in 10 of the 21 selected islands to examine the relationship between ecological conditions, resource governance, food system dynamics, and dietary patterns. Ultimately, this research has created a baseline for future Integrated HIES assessments to simultaneously monitor change in ecological, social, economic, and human health conditions and how they co-vary over time.

A food web bioaccumulation model for the accumulation of per- and polyfluoroalkyl substances (PFAS) in fish: how important is renal elimination?

Per- and polyfluoroalkyl substances (PFAS) are a large class of highly fluorinated anthropogenic chemicals. Some PFAS bioaccumulate in aquatic food webs, thereby posing risks for seafood consumers. Existing models for persistent organic pollutants (POPs) perform poorly for ionizable PFAS. Here we adapt a well-established food web bioaccumulation model for neutral POPs to predict the bioaccumulation behavior of six perfluoroalkyl acids (PFAAs) and two perfluoroalkyl ether acids (HFPO-DA, 9-Cl-PF3ONS) produced as PFAA replacements. The new model includes sorption to blood plasma proteins and phospholipids, empirically parameterized membrane transport, and renal elimination for PFAAs. Improved performance relative to prior models without these updates is shown by comparing simulations to field and lab measurements. PFAS with eight or more perfluorinated carbons (ηpfc ≥ 8, i.e., C8 perfluorosulfonic acid, C10-C11 perfluorocarboxylic acid, 9-Cl-PF3ONS) are often the most abundant in aquatic food webs. The new model reproduces their observed bioaccumulation potential within a factor of two for >80% of fish species, indicating its readiness to support development of fish consumption advisories for these compounds. Results suggest bioaccumulation of ηpfc ≥ 8 PFAS is primarily driven by phospholipid partitioning, and that renal elimination is negligible for these compounds. However, specific protein binding mechanisms are important for reproducing the observed tissue concentrations of many shorter-chain PFAAs, including protein transporter-mediated renal elimination. Additional data on protein-binding and membrane transport mechanisms for PFAS are needed to better understand the biological behavior of shorter-chain PFAAs and their alternatives.

Multidecadal declines in particulate mercury and sediment export from Russian rivers in the pan-Arctic basin.

SignificanceRussian rivers are the predominant source of riverine mercury to the Arctic Ocean, where methylmercury biomagnifies to high levels in food webs. Pollution controls are thought to have decreased late-20th-century mercury loading to Arctic watersheds, but there are no published long-term observations on mercury in Russian rivers. Here, we present a unique hydrochemistry dataset to determine trends in Russian river particulate mercury concentrations and fluxes in recent decades. Using hydrologic and mercury deposition modeling together with multivariate time series analysis, we determine that 70 to 90% declines in particulate mercury fluxes were driven by pollution reductions and sedimentation in reservoirs. Results suggest that Russian rivers likely dominated over all other sources of mercury to the Arctic Ocean until recently.