Hydra's Scenes of Per- and Polyfluoroalkyl Substances (PFAS): Occurrence and Removal Across Environments

Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) are emerging contaminants, where some are known to harm ecological and human health. Due to their widespread use, PFAS have become commonly detected in aquatic environments, which serve both as pathways and as reservoirs for these pollutants. This study provides the first full quantitative national overview of 41 PFAS compounds in English waterbodies (surface water, groundwater, coastal, and estuarine; n=850), using High-Performance Liquid Chromatography-Triple Quadrupole Mass Spectrometry (HPLC-QQQ). Individual PFAS concentrations at 475 sites ranged from 0.0052 to 480ng/L while ΣPFAS concentrations per site ranged from 0.024 to 2021ng/L. Monitoring detected the highest concentrations near large distinct urban areas, though PFAS were also present in rural and undeveloped regions, highlighting the importance of detections across different land use. PFOA was one of the most frequently detected PFAS across all waterbodies, consistent with other studies. No clear correlations were found between PFAS physiochemical properties (chain length and functional group) and concentrations, this may be due to the sampling approach focused which focused on an assessment of background concentrations, rather than point-source, pollution. However, shorter chain PFAS compounds dominated detections in surface waters compared to groundwater. Physical properties and PFAS exposure in waterbodies may play a large role in PFAS detections, as higher concentrations were found in surface water relative to groundwater. Future research should explore PFAS trends over time, consider groundwater sampling depths, examine a broader range of land uses, and assess transboundary PFAS transport to better understand PFAS flux in aquatic systems.

Invited Perspective: Challenges in Evaluating the Effect of Per- and Polyfluoroalkyl Substance Mixtures on Polycystic Ovarian Syndrome

Perfluoroalkyl and polyfluoroalkyl substances in the lower atmosphere and surface waters of the Chinese Bohai Sea, Yellow Sea, and Yangtze River estuary

Opposite page: Sampling for per- and polyfluoroalkyl substances (PFAS) in a stream that wastewater discharges into. Photo courtesy of Linda Lee. Half a century ago, in response to burning rivers and other high-profile environmental disasters, the U.S. Congress passed the Clean Water Act (CWA) as a means to protect waterways from sea to shining sea. Commemorating that landmark legislation, the Journal of Environmental Quality this year has published a collection of papers celebrating the CWA. CSA News magazine is highlighting some of that work through a three-part series. In September, we looked at research (https://doi.org/10.1002/csan.20828) on how constructed wetlands can decrease nutrient runoff on tile-drained agricultural fields. In October, we examined what scientists have learned about the benefits and challenges of using biosolids to fertilize crops, rehabilitate contaminated landscapes, and boost soil health (https://doi.org/10.1002/csan.20853). This final story in the series discusses recent research on emerging contaminants—chemicals suspected of harming people and the environment. From “forever chemicals” to disinfection by-products, and from pharmaceuticals to the lithium batteries that we too often toss in the trash, these pollutants are resulting in unintended consequences that scientists are working hard to understand. Chemicals can be convenient, useful, even lifesaving. We love them when they keep food from sticking to stuff or help us apply lipstick with ease. We love them when they power our cars, computers, and cell phones. We love them when they protect us from diseases. We love them when they make our drinking water safe. But once we’re done with them—once we have thrown them in the trash, washed them down the sink, or flushed them down the loo—they can become a lot less loveable. Some benign compounds transform into harmful ones. Some toxic molecules defy degradation. One-time helpmates can even turn deadly when they end up where we never intended—in our soil, food, tap water, and air. Welcome to the ominous world of emerging contaminants, a vast group encompassing hormones, novel pesticides, nanoparticles, microplastics, disinfection by-products (DBPs), pharmaceuticals and personal care products (PPCPs), and per- and polyfluoroalkyl substances (PFAS). Although “emerging” suggests something novel, some of these pollutants have been around for decades. But building the scientific case for regulating these contaminants is a time-consuming, costly, and often controversial process. Alex Chow, a professor in the Department of Forestry and Environmental Conservation at Clemson University, believes it is high time we learned from our mistakes. In a recent article (https://doi.org/10.1002/jeq2.20405) published in the Journal of Environmental Quality (JEQ), Chow argues that society must be more proactive about preventing contamination from chemicals whose effects may not yet be understood. Over the decades, he has watched the same story unfold over and over as if stuck on repeat: A new compound with promising applications is synthesized; it is embraced by the public and hailed by scientists, perhaps even winning a Nobel Prize (as did DDT and plastics). Eventually, the compound reveals its dark side, leaving scientists and policymakers with a costly environmental and public health mess. He now sees the same story playing out with lithium. Alex Chow collects water samples at the University of California–Berkeley’s Sagehen Field Creek Station for a study on nutrients and pyrogenic dissolved organic carbon in surface water runoff. Photo courtesy of Alex Chow. “Our Society does not recognize it, does not learn from it,” says Chow, an SSSA and ASA member. He advocates taking a more proactive approach to managing the lithium widely used in batteries before it becomes the next Nobel Prize-winning environmental menace. Soil coring for transport studies of per- and polyfluoroalkyl substances (PFAS). Photo courtesy of Linda Lee. Below we introduce you to a trio of scientists who have dedicated their careers to mitigating the fallout from three classes of emerging contaminants: DBPs, PFAS, and PPCPs. Motivated by a love of the environment, they study these compounds from multiple angles—formation and transformation, fate and transport, remediation and prevention. Between the shifting regulatory landscape, the need to detect pollutants at ever more minute concentrations, and how intricately these compounds are enmeshed in our lives, the field keeps researchers on their toes. “I feel like we’re working in an ever-changing landscape,” says Purdue University researcher Linda Lee, an SSSA and ASA member who has been in the field for decades, “a rapidly changing landscape.” As a girl, fish net in tow, Heather Preisendanz would hunt for newts, salamanders, and—her favorite—frogs in the wetlands, vernal pools, and lakes of northern New Jersey. In support of her zeal for amphibians, her family even built a pond in the backyard. “I remember hatching tadpoles as a kid and just being so amazed that this creature could start as an egg, hatch into a tadpole, and then metamorphose into a frog,” recalls Preisendanz, an SSSA member. “These were creatures that I cared about protecting. And once I realized how sensitive they can be to all the pollutants in the environment, then that turned into, I guess, what it is now.” What it is now is a career devoted to keeping bad stuff out of water. As an associate professor of agricultural and biological engineering at Penn State University, Preisendanz studies emerging contaminants like PPCPs. The COVID-19 pandemic presented her team with a unique opportunity to study what happened to our wastewater while millions of people were taking drugs to treat the virus at home and in hospitals. For a study recently published in JEQ (https://doi.org/10.1002/jeq2.20398), Preisendanz and her colleagues spent a year mid-pandemic collecting samples of wastewater as it entered (influent) and then left (effluent) two treatment facilities in Pennsylvania. One is the facility that treats Penn State’s wastewater to the state’s “class B” standard before repurposing it for irrigation on a tract of university land called the Living Filter. The other is the facility that serves the surrounding area, including a hospital, which treats wastewater to the state’s “class A+” standard before using some for irrigation and discharging the rest into a nearby stream. Preisendanz’s team tested the samples for SARS-CoV-2, the virus that causes COVID-19, as well as for prescription and over-the-counter drugs used to treat the virus. They then looked for correlations between what they found in the wastewater, COVID infection and hospitalization rates, and the number of students on campus. “We started at the most basic,” Preisendanz says. “Do we see any trends with the COVID case numbers? And then: Do we see any trends with hospitalizations?” They observed some correlations they expected: For the university samples, for example, antibiotics showed up when students were on campus but not when they weren’t. However, when COVID infection rates rose in the community, they did not see a corresponding bump in over-the-counter drugs in wastewater. Rather, variations in those levels appeared to be seasonal. Similarly, when COVID hospitalizations increased, they saw in their samples no rise in the prescription drugs used to treat the disease. Treated wastewater effluent is sprayed at Penn State’s beneficial reuse site, called the “Living Filter.” This diverts the wastewater from Spring Creek and allows the soil to act as a natural filter for any chemical residuals that remain in the wastewater. Penn State’s Heather Preisendanz has studied the effluent for emerging contaminants. Photo by Heather Preisendanz. At first, this left the scientists scratching their heads. Then they drilled down to more specific data on the number of COVID patients on ventilators, who typically receive dexamethasone. That’s when the correlations began to emerge from the data. Kristin Cochran, a Ph.D. student in the lab of University of South Carolina chemist Susan Richardson, conducts a liquid-liquid extraction of drinking water to analyze disinfection by-products (DBPs). Photo courtesy of Susan Richardson. Demand for disinfectants surged during the COVID pandemic, adding to the wastewater stream more chemicals that, under the right circumstances, could transform into harmful disinfection by-products (DBPs). “You really had to look specifically for what the medicine was being used to treat, and then the numbers made sense,” Preisendanz says. More head scratching ensued when the team detected traces of remdesivir in campus wastewater: There were no hospitalized COVID patients on campus. After a bit of sleuthing, however, they learned that a lab was running experiments using the drug around the time they detected it in the wastewater. When comparing treated wastewater, the team found that the community facility, which treated the wastewater to a higher standard, did a better job at removing some pharmaceuticals than the campus facility. They also found that, in the effluent at both facilities, levels of some pharmaceuticals remained high enough to threaten aquatic organisms. To Preisendanz, the finding highlighted how important it was to filter the effluent through soil before it would eventually reach those organisms, as both facilities do, or to release it into streams that can immediately dilute it with fresh water. Unfortunately, notes Preisendanz, not all areas of the country can offer those ecosystem services. “In more arid portions of the U.S., that’s just not true,” she says. “There, effluent is a larger portion of the streamflow, and so there is less opportunity for the streams to dilute out contaminants. If what we’re seeing holds true to other wastewater treatment facilities where these chemicals are persisting and there is less dilution happening, then potentially the risk could be higher in those areas.” Preisendanz’s work had previously focused on, as she describes it, “what’s at the end of the pipe and where it goes after it is released into the environment.” But this new study also showcases the epidemiolocal applications of wastewater and what it can tell you about the health of the population that generated it. By monitoring wastewater for pathogens or pharmaceuticals, she says, treatment facilities can alert communities about potential public health issues—and help scientists get more bang for their research buck. “These are not cheap compounds to analyze for,” Preisendanz says. The data could be leveraged through collaborations with public health experts, universities, prisons, and municipalities. “It opened the window for us to think about what we are doing differently, as having connections back to human health on the upstream side, and not just the implications after the fact.” In addition to drugs and the virus itself, there’s another class of compounds COVID helped boost in wastewater: disinfectants. Demand for disinfectants surged during the pandemic, adding to the wastewater stream more chemicals that, under the right circumstances, could transform into harmful DBPs. Disinfectants such as chlorine, widely used in public water systems, react with naturally occurring organic matter, bromide, and iodide to create DBPs, some of which have been linked to cancer and other health problems. According to Susan Richardson, a leading expert in DBPs and a professor of chemistry at the University of South Carolina (USC), more than 700 variations of the compounds have been discovered in drinking water to date. Many were first identified in her own lab, including the recent discovery of an entirely new class of them. Richardson has water in her blood, she says. She grew up on St. Simons Island off the Georgia coast where she swam, crabbed, and explored the maritime forests. These days, she uses her off time to scuba dive in tidal rivers and hunt for fossils. Her discoveries include a six-inch-tall megalodon tooth: She was so excited to find it, she recalls, that she screamed into her regulator. “You’re holding a piece of an animal in your hand that was alive millions of years ago,” Richardson says. “It’s like holding history.” Her day job also involves hunting in water. But the specimens she looks for in drinking water are even harder to spot than dinosaur fossils—and a lot more dangerous. Richardson has spent more than three decades ferreting out DBPs using mass spectrometry, first at the USEPA, and more recently at her own lab at USC. Richardson is also concerned about PFAS; she has developed a new method that screens for them by measuring the total organic fluorine in a sample. But she reserves the bulk of her scientific energy for DBPs, which she believes pose the much greater threat. Like PFAS, they are found in most waters but in far higher concentrations—micrograms per liter rather than nanograms. The epidemiologic data, she argues, indicate DBPs are much more toxic to people than PFAS. “We’ve got bladder cancer, we’ve got a little bit of colorectal cancer,” Richardson says. “And then there’s some more recent studies that show miscarriage and birth defects.” Richardson worries DBPs are losing ground to PFAS in the competition for funding and public awareness. To understand this, it helps to know how the USEPA makes tough choices about which contaminants to regulate in drinking water. The process, managed through the Safe Drinking Water Act (or SDWA, which followed the CWA by two years), takes place in five-year cycles. The National Primary Drinking Water Regulations (NPDWR) currently cover dozens of contaminants, including 11 DBPs. The agency periodically updates a contaminant candidate list, the first step for considering a compound for regulation. Some candidates end up on a much shorter list of contaminants that public water systems are required to monitor. Based in part on that data, the USEPA selects a few new compounds to regulate every cycle. Dr. Tamie Veith, a research scientist with the USDA-ARS who collaborates with Penn State’s Heather Preisendanz, downloads hydrologic and water quality data from a monitoring station in Pennsylvania’s Halfmoon Creek watershed. The monitoring station records data every 15 minutes for water level, temperature, dissolved oxygen, and rainfall. Photo by Heather Preisendanz. When, at the end of 2021, the USEPA published its latest list of contaminants to monitor, all but one of the 30 pollutants–lithium–were PFAS. The agency had to pick which poisons to target with its limited resources, and it picked PFAS. Many saw the move as long overdue: Currently, the USEPA doesn’t regulate any PFAS in drinking water (although it recently issued new health advisories). While disappointed by the USEPA’s choices, Richardson continues to build her case against DBPs, like a prosecutor determined to nail a crime ring. One key challenge has been finding the worst of the bunch. “There are definite human health effects, but we still don’t exactly know which DBP’s are the culprits,” Richardson says. “That’s what’s been driving me.” Recently, Richardson narrowed in on those culprits. With a team that includes longtime collaborator Michael Plewa, now a professor emeritus of genetics at the University of Illinois Urbana-Champaign, she produced what the authors call the most comprehensive investigation of drinking water toxicity to date. They collected drinking water from across the U.S. that had been impacted by factors such as agricultural runoff, seawater, wastewater, and algal blooms. Then, using mass spectrometry, Richardson’s team tested each sample for 72 DBPs, many of which had originally been discovered by her lab. After characterizing the samples, she sent extracts to Plewa, who exposed them to mammalian cells. The team then correlated the data to see which caused the most damage. Richardson had a pretty good idea which compound would prove the worst offender: iodoacetic acid, a DBP she had discovered in 2004. She recalls the thrill of spying the pointy peak that denoted the new chemical as it jutted up from the x axis of her mass spec results like a tooth from a dino’s jaw. Penn State lab technician Bill Clees filters a wastewater effluent sample that will be analyzed for pharmaceuticals. Photo by Heather Preisendanz. “I had looked for them, hunted for them in the past, didn’t see them,” she remembers. “And all of a sudden, we’re seeing them big as you please in drinking water.” As with other DBPs, she knew it was a disinfection by-product because the chemical shows up in treated drinking water but not in the source water. After discovering its unique chemical fingerprint and confirming its makeup, she sent a batch to Plewa for toxicology tests. “Oh my God,” he reported, as Richardson recalls. “Iodoacetic acid is the most genotoxic thing I’ve ever looked at. It was like an atomic bomb going off on my cell plates.” In the recent toxicity study, team that iodoacetic with another group called were important of drinking water correlated the most with the observed toxicity of the drinking waters class is by the one of the DBP classes the USEPA does shows no the scientists In other the USEPA the a few while the DBP off the the side, Richardson a of the toxic they would be for the USEPA to with are having to turn to quality water potential DBP from or other to Richardson. Recently, she has been water from South Carolina lakes by In a published this she and her found that, when water as little as 15 of the the of DBPs some of the most than runoff to the algal Richardson Unfortunately, those now not help for many years to if all that that be to because to up the from the she says. The of with a that have been true for other scientists emerging contaminants. For Lee, a professor of environmental that through as she about her research on PFAS, toxic compounds so widely as “forever and As an she her and from one to the At the University of she followed an in chemistry with a in environmental engineering while also working in a lab before a Ph.D. in soil chemistry and contaminant Then it was off to Purdue to and study antibiotics and in In the after as an expert in emerging contaminants, she got a call from The chemical which at the time was under for its and of PFAS, to her a to study the as I see no recalls of realized that they to the environmental of PFAS and how to analyze them. It not have in the they had but they knew that they had to have data, of their own did not well for whose PFAS had to up to the chemical The has been in of millions in and to an While of at the of this the once class of chemicals they through products like is now a The compounds have made were the of a have been the target of regulatory If there was a for emerging contaminants, PFAS would be it. of some products that could be of per- and polyfluoroalkyl substances (PFAS). They are to their and in like makeup, and where their are courtesy of With her a new mass began PFAS, and never looked Over decades, she has studied the compounds in wastewater, drinking water, and at the she once called home where decades of have in the She with Purdue and health scientists to their harmful effects on and as well as and used as animal to on In one recent she and her its from to She even and has been a treatment on carbon that PFAS. Her research as as the compounds PFAS are to their and in like makeup, and where their are There are to of PFAS out says, on how you They are the of the chemical to their They but could to Alex Chow, a professor in the Department of Forestry and Environmental Conservation at Clemson and more are key to lithium he says. Photo courtesy of “It really hard for to PFAS out of their products because in their facility from or are still being used for some says. She She has the same in her own lab. of organic we we have to it for In the U.S., the USEPA has been PFAS including over the next few years to PFAS and other emerging contaminants in drinking water. The agency released new drinking water health for some PFAS, them to the levels of per for the class called and per for the class called part per is hard to It is one in the of water it takes to and are the most of PFAS and the most In the USEPA issued a to both as substances under the Although and still the U.S. in products from other have them. But they are still in this the U.S. by a as has One group of PFAS found in food and other U.S. products is not yet these compounds end up in the portion of what out of wastewater treatment can be used as while the from or But once the PFAS in those biosolids can on a of their own as and her recently The research team examined what out of biosolids over a other they observed that the of group that includes the candidates and the far what had been in the biosolids is the of other PFAS like The toxic with these “That’s we PFAS says. “It’s PFAS to The surrounding the fate and transport of PFAS in biosolids has some communities to or even its suggests taking a few back to see the we need to is out in what to apply them, and are there that we can PFAS from the says. the idea that they be or is the of what we to for to be The harmful effects of she are of than those of “We need to on up the areas contaminated by of and biosolids and not all the PFAS to be that you your says. “We’ve a lot of in to be more are and can be hard to people can on where to regulatory and there are a lot of there are on emerging contaminants. One may be But on this the scientists More funding for this and at keeping pollutants out of the to will The in PFAS funding across is up the field says. a lot and not going What it means is that be to a lot more in all areas.” Penn State’s Preisendanz, for example, has to her emerging contaminant to PFAS. She and was on Preisendanz’s Ph.D. at are on an study on PFAS in well water, the source of drinking water for of Preisendanz also a recent study the PFAS of decades of irrigation at Penn State’s Living Her team detected PFAS across its with on While levels were they drinking water levels being by the for and as well as the USEPA’s new health about the of with treated wastewater. is key to the public and says. I to see is being to with the and that have them,” she says. to get every including the to that their choices can make even at the group has a for people who to products with Purdue to to a for the side, has or is in the of PFAS in food and other are could also boost lithium says Chow, which the USEPA’s on lithium batteries as a and more are key to lithium he says, which is to of people in the U.S. have potentially harmful levels of the in their water to the U.S. think lithium is and because at he says. if we them they will get at higher and higher Then I will a In our is celebrating the Clean Water with two new In the first Dr. Alex Chow discusses how we can a proactive approach to lithium In the Dr. discusses years of biosolids research in us at or through your for to never an

Perfluoroalkyl substances (PFAS) are the member of that class of compounds which includes at least one fluorine atom in their structure, are being used in various industrial and consumer products due to their unique chemical properties. Perfluorooctanoic sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) are the most important and well-known components among PFAS. Perfluoroalkyl and polyfluoroalkyl substances (PFAS) exert various kinds of effects on living organisms, but the most serious ones are the metabolic effects. However, PFAS are inert metabolically itself, but they interfere with endogenous metabolic pathways and reactions, and indirectly affect the metabolism of the body. Unluckily, there are many other PFAS to those humans are exposed throughout their life which not only imparts harmful effects on adults but also in whole life. It has been quantified that PFAS are present in amniotic fluid, fetal tissue, breastmilk, lung, heart, umbilical cord, and brain, blood, and placenta which indicates PFAS exposure in infants from the very start of life. PFAS exposure to Nematodes for 72 h shows the evidence of neuropathology during the inspection of GABAergic, dopaminergic, serotoninergic, and cholinergic neuronal morphologies. Ingestion of mycotoxins causes complex problems to human health. Physio-chemical processing aimed to destroy and mineralize contaminants into carbon dioxide and water or less toxic products.

Perfluoroalkyl acids (PFAAs) in the Pra and Kakum River basins and associated tap water in Ghana.

Toxicological mode-of-action and developmental toxicity of different carbon chain length PFAS.

Sixty leading members of the scientific, engineering, regulatory, and legal communities assembled for the PFAS Experts Symposium in Arlington, Virginia on May 20 and 21, 2019 to discuss issues related to per‐ and polyfluoroalkyl substances (PFAS) based on the quickly evolving developments of PFAS regulations, chemistry and analytics, transport and fate concepts, toxicology, and remediation technologies. The Symposium created a venue for experts with various specialized skills to provide opinions and trade perspectives on existing and new approaches to PFAS assessment and remediation in light of lessons learned managing other contaminants encountered over the past four decades. The following summarizes several consensus points developed as an outcome of the Symposium: Regulatory and policy issues: The response by many states and the US Environmental Protection Agency (USEPA) to media exposure and public pressure related to PFAS contamination is to relatively quickly initiate programs to regulate PFAS sites. This includes the USEPA establishing relatively low lifetime health advisory levels for PFAS in drinking water and even more stringent guidance and standards in several states. In addition, if PFAS are designated as hazardous substances at the federal level, as proposed by several Congressional bills, there could be wide‐reaching effects including listing of new Superfund sites solely for PFAS, application of stringent state standards, additional characterization and remediation at existing sites, reopening of closed sites, and cost renegotiation among PRPs. Chemistry and analytics: PFAS analysis is confounded by the lack of regulatory‐approved methods for most PFAS in water and all PFAS in solid media and air, interference with current water‐based analytical methods if samples contain high levels of suspended solids, and sample collection and analytical interference due to the presence of PFAS in common consumer products, sampling equipment, and laboratory materials. Toxicology and risk: Uncertainties remain related to human health and ecological effects for most PFAS; however, regulatory standards and guidance are being established incorporating safety factors that result in part per trillion (ppt) cleanup objectives. Given the thousands of PFAS that may be present in the environment, a more appropriate paradigm may be to develop toxicity criteria for groups of PFAS rather than individual PFAS. Transport and fate: The recalcitrance of many perfluoroalkyl compounds and the capability of some fluorotelomers to transform into perfluoroalkyl compounds complicate conceptual site models at many PFAS sites, particularly those involving complex mixtures, such as firefighting foams. Research is warranted to better understand the physicochemical properties and corresponding transport and fate of most PFAS, of branched and linear isomers of the same compounds, and of the interactions of PFAS with other co‐contaminants such as nonaqueous phase liquids. Many PFAS exhibit complex transport mechanisms, particularly at the air/water interface, and it is uncertain whether traditional transport principles apply to the ppt levels important to PFAS projects. Existing analytical methods are sufficient when combined with the many advances in site characterization techniques to move rapidly forward at selected sites to develop and test process‐based conceptual site models. Existing remediation technologies and research: Current technologies largely focus on separation (sorption, ion exchange, or sequestration). Due to diversity in PFAS properties, effective treatment will likely require treatment trains. Monitored natural attenuation will not likely involve destructive reactions, but be driven by processes such as matrix diffusion, sorption, dispersion, and dilution. The consensus message from the Symposium participants is that PFAS present far more complex challenges to the environmental community than prior contaminants. This is because, in contrast to chlorinated solvents, PFAS are severely complicated by their mobility, persistence, toxicological uncertainties, and technical obstacles to remediation—all under the backdrop of stringent regulatory and policy developments that vary by state and will be further driven by USEPA. Concern was expressed about the time, expense, and complexity required to remediate PFAS sites and whether the challenges of PFAS warrant alternative approaches to site cleanups, including the notion that adaptive management and technical impracticability waivers may be warranted at sites with expansive PFAS plumes. A paradigm shift towards receptor protection rather than broad scale groundwater/aquifer remediation may be appropriate.

BackgroundExposure to per- and polyfluoroalkyl substances (PFAS) has been linked with various cancers. Assessment of PFAS in drinking water and cancers can help inform biomonitoring and prevention efforts.ObjectiveTo screen for incident cancer (2016–2021) and assess associations with PFAS contamination in drinking water in the US.MethodsWe obtained county-level age-adjusted cancer incidence (2016–2021) from the Surveillance, Epidemiology, and End Results (SEER) Program. Data on PFAS levels in public drinking water systems were obtained from the Third (UCMR3; 2013–2015) and Fifth (UCMR5; 2023–2024) Unregulated Contaminant Monitoring Rule. UCMR3 measured PFOS, PFOA, PFNA, PFHxS, PFHpA, and PFBS. UCMR5 expanded measurements to include PFBA, PFHxA, PFPeA, and PFPeS. We created indicators of PFAS detection and, for UCMR5, concentrations above Maximum Contaminant Levels (MCLs). MCLs for PFOA and PFOS are 4 ng/L, and for PFNA and PFHxS are 10 ng/L. We used Poisson regression models to assess associations between PFAS detection or MCL violation and cancer incidence, adjusting for potential confounders. We estimated the number of attributable cancer cases.ResultsPFAS in drinking water was associated with increased cancer incidence in the digestive, endocrine, oral cavity/pharynx, and respiratory systems. Incidence rate ratios (IRRs) ranged from 1.02 to 1.33. The strongest association was observed between PFBS and oral cavity/pharynx cancers (IRR: 1.33 [1.04, 1.71]). Among males, PFAS was associated with cancers in the urinary, brain, leukemia, and soft tissues. Among females, PFAS was associated with cancers in the thyroid, oral cavity/pharynx, and soft tissue. PFAS in drinking water is estimated to contribute to 4626 [95% CI: 1,377, 8046] incident cancer cases per year based on UCMR3 data and 6864 [95% CI: 991, 12,804] based on UCMR5.Impact statementThe ecological study examined the associations between PFAS in drinking water measured in two waves (2013–2015 and 2023–2024) and cancer incidence between 2016 and 2021. We found that PFAS in drinking water was associated with cancers in the organ system including the oral cavity/pharynx, lung, digestive system, brain, urinary system, soft tissue, and thyroid. Some cancers have not been widely studied for their associations with PFAS. We also observed sex differences in the associations between PFAS and cancer risks. This is the first ecological study that examined PFAS exposure in drinking water and various cancer risks.

Time-dependent effects of perfluorinated compounds on viability in cerebellar granule neurons: Dependence on carbon chain length and functional group attached

Polyfluoroalkyl and perfluoroalkyl substances (PFAS) are persistent organic pollutants and exposure have been suggested with the risk of developing preeclampsia. Yet, evidence on the associations of PFAS with preeclampsia is still conflicting. Thus, the current study conducted a systematic review and meta-analysis of the epidemiological evidence linking maternal PFAS exposure to preeclampsia. This research methodology involved searching three electronic databases for epidemiological studies, and then conducting a meta-analysis using a random-effects model to analyse the heterogeneity between the studies. The quality and strength of evidence for each exposure-outcome pair was also evaluated, as well as the risk of bias. The search identified 10 potentially eligible studies related to maternal PFAS blood level with preeclampsia, which 7 were ultimately selected. Meta-analysis demonstrated evidence of association between combined PFAS compounds in pregnant mother with preeclampsia with zero heterogeneity (I2=0.0%, Q= 3.09, df= 6, p=0.798). Preeclampsia was found to have moderate association with maternal perfluorooctanoic acid (PFOA) exposure (Test for overall effect: z=2.2, p=0.03; Test for heterogeneity: I2=0.0%, Q= 3.49, df= 6, p=0.745) as well as maternal perfluorooctane sulfonate (PFOS) exposure (Test for overall effect: z=2.5, p=0.01; Test for heterogeneity: I2=0.0%, Q= 3.70, df= 6, p=0.718). This study showed significant associations between PFOA and PFOS exposure with the risk of preeclampsia. However, in-depth investigation is imperative to elucidate the impact of the different concentration and types of PFAS on preeclampsia risk.

Model-based identification of vadose zone controls on PFAS mobility under semi-arid climate conditions

<p dir="ltr">Per- and polyfluoroalkyl substances (PFAS) are a group of synthetic chemicals, abundantly produced and with a wide range of applications. The partial or full fluorination of alkyl substances with varying functional groups, leads to physicochemical properties that are mainly characterised by persistence and amphiphilicity. While these properties are highly valuable for industrial- and consumer products, they pose major challenges in environmental pollution and health implications. Especially influences on the lipid metabolism have been frequently connected to PFAS exposures, yet lack deeper mechanistic understanding, and were, hence, the main investigated experimental subject of this thesis.</p><p dir="ltr">Regulatory efforts for PFAS have been made in the past and are currently underway. A harmonised approach for the assessment of human health effects, following PFAS exposure is, however, still needed. Dose-response assessment, through benchmark dose (BMD) modelling is the state of the science for hazard characterisation for risk assessment purposes. Specifically, the selection of a critical effect size (CES) - a threshold for adversity - of the assessed effect (response), is important in this context.</p><p dir="ltr">This thesis set out to tackle the outlined challenges in toxicological assessments of PFAS in three main approaches.</p><p dir="ltr">1) Testing contrasting ways to select the CESs in different BMD modelling approaches and assess the outcome metrics for select PFAS case-studies (Study I).</p><p dir="ltr">2) Utilise human cell models to gain insights into PFAS-effects on the human lipid metabolism. This was done by investigating PFAS (single and mixture) exposures and PPARa receptor activation, lipid metabolism-related gene expression and lipid accumulation in Study III. Further, PFAS (single) exposure was investigated with regards to affecting hepatocyte lipidomic profiles in Study II.</p><p dir="ltr">3) Assessing the meaningfulness of comparative relative potency factors (RPFs) for PFAS, through characterisation of RPFs, based on the endpoints in Study III.</p><p dir="ltr">The findings of Study I reveal that the CES choice alters the results of a dose- response assessment significantly for both, frequentist and Bayesian BMD modelling. Further, it became apparent that for the selected case-studies, the Bayesian BMD modelling - paired with flexible, effect-specific CES selection - led to more stable and biologically relevant results, supporting their use in regulatory decision-making.</p><p dir="ltr">Study II unveiled wide-range influences of PFAS exposures on the intracellular (hepatocyte) lipid profile. Legacy PFAS (e.g., PFOS and PFOA), as well as substitute PFAS (e.g., HFPO-DA and ADONA), were shown to have lipid profile-altering properties, with PFOS and PFOA having displayed the largest effects.</p><p dir="ltr">The cell-based assays in Study III confirmed PFAS influences in multiple mechanistic steps of the lipid metabolism. This further underscores the body of evidence for the investigated PFAS and PFAS mixtures to be involved in alterations of important lipid metabolic pathways with likely relevance to cardiovascular diseases and other metabolic conditions. With regards to their relative potencies, PFAS appeared to be endpoint-specific, with no unambiguous pattern of potency.</p><p dir="ltr">This thesis offers an assessment of the BMD methodology in chemical hazard characterisation within the context of assessing the risks from PFAS. Further, multi-endpoint assessment and exposures to single PFAS and PFAS mixtures of human relevance, highlighted the importance of the lipid metabolism as a major target system for PFAS toxicity. The use of RPFs to compare PFAS effects in an endpoint-specific manner, however, needs to be further investigated and a universal approach across endpoints appears to be very challenging.</p><h3>List of scientific papers</h3><p dir="ltr">I. BRUNKEN, L., Vieira Silva, A., & Öberg, M. (2025). Selection of the critical effect size alters hazard characterization - a retrospective analysis of key studies used for risk assessments of PFAS. Frontiers in Toxicology. 7. <a href="https://doi.org/10.3389/ftox.2025.1525089" rel="noreferrer" target="_blank">https://doi.org/10.3389/ftox.2025.1525089</a></p><p dir="ltr">II. Kashobwe, L.#, Sadrabadi, F.#, BRUNKEN, L.#, Coelho, A. C. M. F., Sandanger, T. M., Braeuning, A., Buhrke, T., Öberg, M., Hamers, T., & Leonards, P. E. G. (2024). Legacy and alternative per- and polyfluoroalkyl substances (PFAS) alter the lipid profile of HepaRG cells. Toxicology. 506, 153862. # Equally contributed. <a href="https://doi.org/10.1016/j.tox.2024.153862" rel="noreferrer" target="_blank">https://doi.org/10.1016/j.tox.2024.153862</a></p><p dir="ltr">III. BRUNKEN, L., Vieira Silva, A., & Öberg, M. Relative Potency of PFAS in Human Cell Models: Linking PPARa Activation, Gene Regulation, and Lipid Accumulation. [Manuscript]</p>

Background Per- and poly-fluoroalkyl substances (PFAS) are a growing public health concern, as they are widely used in industry and consumer products and some studies have shown associations between high PFAS exposure and adverse health effects. EPA monitors PFAS in public water systems (PWS) with the unregulated contaminant monitoring rule (UCMR). The National Academies of Science, Engineering, and Medicine (NASEM) published clinical and laboratory direction that 9 PFAS should be measured in serum and a summed total PFAS used to guide clinical care based on two categories: usual standard of care appropriate for age for most individuals at = 20 ng/mL summed PFAS; and additional testing, follow-up and further exposure reduction for individuals with a PFAS sum >20 ng/mL who may be at increased risk of PFAS-related adverse health effects. To better understand the correlation between PFAS contamination in drinking water and PFAS in serum in clinical populations, a prospective study was conducted with specimens collected from zip codes with low and high PFAS exposure. Methods Zip codes with low PFAS exposure were identified from PWS IDs in UCMR3 and UCMR5 with all measured PFAS below minimum reporting levels (MRLs). Zip codes with high PFAS exposure were determined by identifying the 25 PWS IDs with the highest individual and summed PFOS, PFOA, and PFHxS in UCMR5 data available as of April 2024. After removing duplicates, checking remnant specimen availability and pairing zip codes for low- and high-exposure groups by state, 20 unique paired PWS ID sets were finalized and used to pull random remnant specimens. With IRB approval, all remnant specimens were deidentified and tested using a recent published method for serum PFAS quantitation of the 9 NASEM-recommended analytes. Wilcoxon rank test and Chi-Square test were used to compare numeric PFAS (summation and individual) and categorical PFAS summation respectively. Results A total of 1,599 remnant specimens were received and tested: 771 in the high-exposure group and 788 specimens in the low-exposure group. Two groups were comparable in sex distribution (high group: female 56.7% and male 43.3%, low group: female 58.4% and male 41.6%) and mean age (high group: 52.0 y/o, low group: 51.1 y/o) (both p>0.4). Mean PFAS summation was 9.2 ng/mL in the high group comparing to 6.1 ng/mL in the low group (p<0.001). Categorically the percentage of people with PFAS summation >20 ng/mL in the high group was 7.1%, which was also significantly higher than 2.8% observed in the low group (p<0.001). Similarly, mean individual PFAS was higher in the high group comparing to the low group for PFOS (3.0 ng/mL vs. 2.2 ng/mL), PFOA (1.6 ng/mL vs. 0.9 ng/mL), and PFHxS (2.0 ng/mL vs. 1.1 ng/mL) (all p<0.001). Conclusion This PFAS study of remnant specimens supports the hypothesis that higher PFAS contamination in public drinking water is associated with higher PFAS serum concentrations in exposed communities. This study supports policies encouraging PFAS testing and treatment at public water systems to reduce potential health effects. Further studies on these remnant specimens will investigate correlations to clinical outcomes.

<p dir="ltr">Per- and polyfluoroalkyl substances (PFAS) are a group of synthetic chemicals, abundantly produced and with a wide range of applications. The partial or full fluorination of alkyl substances with varying functional groups, leads to physicochemical properties that are mainly characterised by persistence and amphiphilicity. While these properties are highly valuable for industrial- and consumer products, they pose major challenges in environmental pollution and health implications. Especially influences on the lipid metabolism have been frequently connected to PFAS exposures, yet lack deeper mechanistic understanding, and were, hence, the main investigated experimental subject of this thesis.</p><p dir="ltr">Regulatory efforts for PFAS have been made in the past and are currently underway. A harmonised approach for the assessment of human health effects, following PFAS exposure is, however, still needed. Dose-response assessment, through benchmark dose (BMD) modelling is the state of the science for hazard characterisation for risk assessment purposes. Specifically, the selection of a critical effect size (CES) - a threshold for adversity - of the assessed effect (response), is important in this context.</p><p dir="ltr">This thesis set out to tackle the outlined challenges in toxicological assessments of PFAS in three main approaches.</p><p dir="ltr">1) Testing contrasting ways to select the CESs in different BMD modelling approaches and assess the outcome metrics for select PFAS case-studies (Study I).</p><p dir="ltr">2) Utilise human cell models to gain insights into PFAS-effects on the human lipid metabolism. This was done by investigating PFAS (single and mixture) exposures and PPARa receptor activation, lipid metabolism-related gene expression and lipid accumulation in Study III. Further, PFAS (single) exposure was investigated with regards to affecting hepatocyte lipidomic profiles in Study II.</p><p dir="ltr">3) Assessing the meaningfulness of comparative relative potency factors (RPFs) for PFAS, through characterisation of RPFs, based on the endpoints in Study III.</p><p dir="ltr">The findings of Study I reveal that the CES choice alters the results of a dose- response assessment significantly for both, frequentist and Bayesian BMD modelling. Further, it became apparent that for the selected case-studies, the Bayesian BMD modelling - paired with flexible, effect-specific CES selection - led to more stable and biologically relevant results, supporting their use in regulatory decision-making.</p><p dir="ltr">Study II unveiled wide-range influences of PFAS exposures on the intracellular (hepatocyte) lipid profile. Legacy PFAS (e.g., PFOS and PFOA), as well as substitute PFAS (e.g., HFPO-DA and ADONA), were shown to have lipid profile-altering properties, with PFOS and PFOA having displayed the largest effects.</p><p dir="ltr">The cell-based assays in Study III confirmed PFAS influences in multiple mechanistic steps of the lipid metabolism. This further underscores the body of evidence for the investigated PFAS and PFAS mixtures to be involved in alterations of important lipid metabolic pathways with likely relevance to cardiovascular diseases and other metabolic conditions. With regards to their relative potencies, PFAS appeared to be endpoint-specific, with no unambiguous pattern of potency.</p><p dir="ltr">This thesis offers an assessment of the BMD methodology in chemical hazard characterisation within the context of assessing the risks from PFAS. Further, multi-endpoint assessment and exposures to single PFAS and PFAS mixtures of human relevance, highlighted the importance of the lipid metabolism as a major target system for PFAS toxicity. The use of RPFs to compare PFAS effects in an endpoint-specific manner, however, needs to be further investigated and a universal approach across endpoints appears to be very challenging.</p><h3>List of scientific papers</h3><p dir="ltr">I. BRUNKEN, L., Vieira Silva, A., & Öberg, M. (2025). Selection of the critical effect size alters hazard characterization - a retrospective analysis of key studies used for risk assessments of PFAS. Frontiers in Toxicology. 7. <a href="https://doi.org/10.3389/ftox.2025.1525089" rel="noreferrer" target="_blank">https://doi.org/10.3389/ftox.2025.1525089</a></p><p dir="ltr">II. Kashobwe, L.#, Sadrabadi, F.#, BRUNKEN, L.#, Coelho, A. C. M. F., Sandanger, T. M., Braeuning, A., Buhrke, T., Öberg, M., Hamers, T., & Leonards, P. E. G. (2024). Legacy and alternative per- and polyfluoroalkyl substances (PFAS) alter the lipid profile of HepaRG cells. Toxicology. 506, 153862. # Equally contributed. <a href="https://doi.org/10.1016/j.tox.2024.153862" rel="noreferrer" target="_blank">https://doi.org/10.1016/j.tox.2024.153862</a></p><p dir="ltr">III. BRUNKEN, L., Vieira Silva, A., & Öberg, M. Relative Potency of PFAS in Human Cell Models: Linking PPARa Activation, Gene Regulation, and Lipid Accumulation. [Manuscript]</p>