Tag: pfas

Machine Learning Predicts Highest-Risk Groundwater Sites to Improve Water Quality Monitoring

 Matt Shipman  

illustration shows a digital screen displaying data related to groundwater quality

For Immediate Release

Yaroslava Yinglingyara_yingling@ncsu.edu

Paul Westerhoffp.westerhoff@asu.edu

Matt Shipmanmatt_shipman@ncsu.edu

An interdisciplinary team of researchers has developed a machine learning framework that uses limited water quality samples to predict which inorganic pollutants are likely to be present in a groundwater supply. The new tool allows regulators and public health authorities to prioritize specific aquifers for water quality testing.

This proof-of-concept work focused on Arizona and North Carolina but could be applied to fill critical gaps in groundwater quality in any region.

Groundwater is a source of drinking water for millions and often contains pollutants that pose health risks. However, many regions lack complete groundwater quality datasets.

“Monitoring water quality is time-consuming and expensive, and the more pollutants you test for, the more time-consuming and expensive it is,” says Yaroslava Yingling, co-corresponding author of a paper describing the work and Kobe Steel Distinguished Professor of Materials Science and Engineering at North Carolina State University.

“As a result, there is interest in identifying which groundwater supplies should be prioritized for testing, maximizing limited monitoring resources,” Yingling says. “We know that naturally occurring pollutants, such as arsenic or lead, tend to occur in conjunction with other specific elements due to geological and environmental factors. This posed an important data question: with limited water quality data for a groundwater supply, could we predict the presence and concentrations of other pollutants?”

“Along with identifying elements that pose a risk to human health, we also wanted to see if we could predict the presence of other elements – such as phosphorus – which can be beneficial in agricultural contexts but may pose environmental risks in other settings,” says Alexey Gulyuk, a co-first author of the paper and a teaching professor of materials science and engineering at NC State.

To address this challenge, the researchers drew on a huge data set, encompassing more than 140 years of water quality monitoring data for groundwater in the states of North Carolina and Arizona. Altogether, the data set included more than 20 million data points, covering more than 50 water quality parameters.

“We used this data set to ‘train’ a machine learning model to predict which elements would be present based on the available water quality data,” says Akhlak Ul Mahmood, co-first author of this work and a former Ph.D. student at NC State. “In other words, if we only have data on a handful of parameters, the program could still predict which inorganic pollutants were likely to be in the water, as well as how abundant those pollutants are likely to be.”

One key finding of the study is that the model suggests pollutants are exceeding drinking water standards in more groundwater sources than previously documented. While actual data from the field indicated that 75-80% of sampled locations were within safe limits, the machine learning framework predicts that only 15% to 55% of the sites may truly be risk-free.

“As a result, we’ve identified quite a few groundwater sites that should be prioritized for additional testing,” says Minhazul Islam, co-first author of the paper and a Ph.D. student at Arizona State University. “By identifying potential ‘hot spots,’ state agencies and municipalities can strategically allocate resources to high-risk areas, ensuring more targeted sampling and effective water treatment solutions”

“It’s extremely promising and we think it works well,” Gulyuk says. “However, the real test will be when we begin using the model in the real world and seeing if the prediction accuracy holds up.”

Moving forward, researchers plan to enhance the model by expanding its training data across diverse U.S. regions; integrating new data sources, such as environmental data layers, to address emerging contaminants; and conducting real-world testing to ensure robust, targeted groundwater safety measures worldwide.

“We see tremendous potential in this approach,” says Paul Westerhoff, co-corresponding author and Regents’ Professor in the School of Sustainable Engineering and the Built Environment at ASU. “By continuously improving its accuracy and expanding its reach, we’re laying the groundwork for proactive water safety measures across the globe.”

“This model also offers a promising tool for tracking phosphorus levels in groundwater, helping us identify and address potential contamination risks more efficiently,” says Jacob Jones, director of the National Science Foundation-funded Science and Technologies for Phosphorus Sustainability (STEPS) Center at NC State, which helped fund this work. “Looking ahead, extending this model to support broader phosphorus sustainability could have a significant impact, enabling us to manage this critical nutrient across various ecosystems and agricultural systems, ultimately fostering more sustainable practices.”

The paper, “Multiple Data Imputation Methods Advance Risk Analysis and Treatability of Co-occurring Inorganic Chemicals in Groundwater,” is published open access in the journal Environmental Science & Technology. The paper was co-authored by Emily Briese and Mohit Malu, both Ph.D. students at Arizona State; Carmen Velasco, a former postdoctoral researcher at Arizona State; Naushita Sharma, a postdoctoral researcher at Oak Ridge National Laboratory; and Andreas Spanias, a professor of digital signal processing at Arizona State.

This work was supported by the NSF STEPS Center; and by the Metals and Metal Mixtures: Cognitive Aging, Remediation and Exposure Sources (MEMCARE) Superfund Research Center based at Harvard University, which is supported by the National Institute of Environmental Health Science under grant P42ES030990.

-shipman-

Note to Editors: The study abstract follows.

“Multiple Data Imputation Methods Advance Risk Analysis and Treatability of Co-occurring Inorganic Chemicals in Groundwater”

Authors: Akhlak U. Mahmood, Alexey V. Gulyuk and Yaroslava G. Yingling, North Carolina State University; Minhazul Islam, Emily Briese, Carmen A. Velasco, Mohit Malu, Naushita Sharma, Andreas Spanias and Paul Westerhoff, Arizona State University

Published: Nov. 7, Environmental Science & Technology

DOI: 10.1021/acs.est.4c05203

Abstract: Accurately assessing and managing risks associated with inorganic pollutants in groundwater is imperative. Historic water quality databases are often sparse due to rationale or financial budgets for sample collection and analysis, posing challenges in evaluating exposure or water treatment effectiveness. We utilized and compared two advanced multiple data imputation techniques, AMELIA and MICE algorithms, to fill gaps in sparse groundwater quality data sets. AMELIA outperformed MICE in handling missing values, as MICE tended to overestimate certain values, resulting in more outliers. Field data sets revealed that 75% to 80% of samples exhibited no co-occurring regulated pollutants surpassing MCL values, whereas imputed values showed only 15% to 55% of the samples posed no health risks. Imputed data unveiled a significant increase, ranging from 2 to 5 times, in the number of sampling locations predicted to potentially exceed health-based limits and identified samples where 2 to 6 co-occurring chemicals may occur and surpass health-based levels. Linking imputed data to sampling locations can pinpoint potential hotspots of elevated chemical levels and guide optimal resource allocation for additional field sampling and chemical analysis. With this approach, further analysis of complete data sets allows state agencies authorized to conduct groundwater monitoring, often with limited financial resources, to prioritize sampling locations and chemicals to be tested. Given existing data and time constraints, it is crucial to identify the most strategic use of the available resources to address data gaps effectively. This work establishes a framework to enhance the beneficial impact of funding groundwater data collection by reducing uncertainty in prioritizing future sampling locations and chemical analyses.

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https://news.ncsu.edu/2024/11/predicting-risk-in-groundwater-supplies/?

Scientists Say This Simple Underground Fix Could Keep PFAS Out of Drinking Water

In real-world testing, researchers found that a carbon-based material placed underground sharply lowered PFAS in groundwater and required minimal maintenance.

By Stacey Leasca

Published on January 16, 2026

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  • Scientists from Brown University, the University of Minnesota, and the U.S. Navy found that injecting colloidal carbon into contaminated soil can trap PFAS chemicals underground, dramatically reducing contamination.
  • In field tests, PFAS concentrations fell from over 50,000 nanograms per liter to undetectable levels within 10 months, capturing both long- and short-chain PFAS compounds.
  • The approach could cost less than half as much as current cleanup methods and require minimal maintenance, offering a sustainable solution for communities dealing with PFAS pollution.

Over decades, per- and polyfluoroalkyl substances (PFAS) have slowly woven their way into our daily lives, without most of us ever noticing. They’re the stuff that prevents your eggs from sticking to the frying pan, waterproofs your jackets, allows makeup to last an entire day, and keeps those fast-food wrappers grease-resistant.

They’re also the stuff that earned the unsettling nickname “forever chemicals” thanks to carbon-fluorine bonds so strong that once these chemicals enter the environment, they tend to stay there. Forever. And that durability has become a serious problem. Scientists are increasingly recognizing that PFAS may cause a range of health issues, even as these chemicals have been detected in groundwater near military bases, airports, industrial sites, and municipal water systems across the United States. Cleaning them up has proven frustratingly difficult, expensive, and often temporary. Public-facing advice has often focused on avoiding products that contain PFAS or relying on above-ground water filtration, which requires almost constant upkeep. But now a few savvy researchers say they may soon have a solution for that, too.

​Researchers from Brown University and the University of Minnesota, alongside industry partners and the U.S. Navy, tested whether an ultrafine carbon material could be injected directly into contaminated soil to trap PFAS in place. Their findings, published in The Journal of Hazardous Materials, show that it may be a wild enough idea to work.

The team tested an activated carbon material known as “colloidal carbon,” which acts like a microscopic sponge that can trap PFAS chemicals underground. They began by trialing it in lab conditions, collecting soil from a contaminated site, before testing it on the real thing, taking it to a field at a Navy training area known to have extremely high PFAS levels.

https://www.foodandwine.com/embed?url=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DP-x-FXvsjTw&id=mntl-sc-block_10-0-iframe&options=e30%3D&docId=11883002

​The researchers ran a “push-pull” test, injecting the carbon into the ground, creating an underground treatment zone where PFAS bind as groundwater flows through the net, then pumping the water back out to measure how much of the PFAS made it through. In their tests, the PFAS concentrations dropped from more than 50,000 nanograms per liter to tktk, below detection limits, within 10 months. Importantly, the carbon net captures both long-chain and short-chain PFAS. This is a big deal for the potential cleanup of these forever chemicals because short-chain PFAS are harder to remove, yet are becoming increasingly common as manufacturers move away from older compounds.

​Just as important from an economic standpoint is that, according to the team’s analysis, the long-term operating costs of this carbon-based approach would be less than half those of the existing PFAS remedies. And because the system would exist underground, it would require little maintenance.

Your Beer May Contain ‘Forever Chemicals,’ According to New Research

“This study shows that we can create an effective treatment zone underground that dramatically reduces PFAS levels with far lower long-term costs,” Matt Simcik, a professor in the School of Public Health and co-author of the study, shared in a statement. “The effectiveness of this method, combined with the fact that the system requires very little ongoing maintenance, makes this a promising option for real-world cleanup efforts. For communities facing PFAS contamination, this represents a major step forward toward practical, sustainable technologies that can protect drinking water and reduce long-term exposure risks.”

​It’s critical to note that this isn’t a silver bullet — at least not yet. The researchers are clear that more work is needed to understand how long underground carbon remains effective and how it could perform under different soil conditions. But the study does offer some good news and a potentially practical path forward in the fight against forever chemicals. And, on a similarly impactful note, it shows just how important it is that we work on this issue together.

​”The project shows the importance of partnerships between practitioners, government, and academia,” William Arnold, a professor in the College of Science and Engineering, said. “The expertise, experience, and insight of the individuals who made up the team were needed for this lab-to-field project to succeed.”

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https://www.foodandwine.com/carbon-based-filter-removes-pfas-in-contaminated-groundwater-11883002?

Improving drinking water quality in the U.S.

By: Jay Lau

Throughout the fall, Harvard Chan faculty will share evidence-based recommendations on urgent public health issues facing the next U.S. administration. Ronnie Levin, instructor in the Department of Environmental Health, offered her thoughts on policies that could address contamination in the country’s drinking water supply.

Q: Why is drinking water quality a pressing public health issue?

A: The U.S. has arguably the best and most reliable drinking water in the world, and that’s because we’ve spent a lot of money and time getting it in that shape. On the other hand, our drinking water is not risk-free. It’s not perfectly safe—it can contain lead, nitrate, PFAS, arsenic, and uranium, as examples. In addition, there are racial and ethnic disparities in contaminant exposures, so not everybody gets the same quality of drinking water.

Q: What are the biggest challenges facing the next administration around improving drinking water quality?

A: A hundred years ago, we sunk a lot of money into water treatment and infrastructure, but then we stopped putting in that kind of investment. Now our water systems are severely aging and deteriorated, and we haven’t continued to maintain the older ones. And when we build new ones, they’re not always as well designed as the old ones.

In addition, science has moved on—we’ve found things in our drinking water that we thought weren’t bad, like PFAS, that turn out to be biologically active at very low levels. Lead, arsenic, and nitrate cause health effects at lower levels than we knew when we set the standards decades ago. We now need to catch up.

Ronnie Levin. Photo: Kent Dayton
Q: What are your top policy recommendations to address drinking water quality?

A: There’s been recent progress toward reducing lead in drinking water. On Oct. 8, the Environmental Protection Agency (EPA) announced a rule that requires all lead pipes in U.S. water systems to be replaced within the next decade, lowers the current level for taking action to reduce lead exposure from 15 to 10 parts per billion, and also implements several other policies to reduce exposure to lead from drinking water. If the rule is implemented and enforced, millions of people will have cleaner, safer water. Importantly, it will particularly enhance environmental protection among disadvantaged and low-income populations, which have been disproportionately impacted by lead-contaminated water.

There are several other contaminants I’d like to see the government address. PFAS are a class of thousands of chemicals that are in all kinds of consumer products. We don’t even know all of them, because industry keeps tweaking them to be different and cheaper, and industry doesn’t have to report how they get used. There are PFAS everywhere, contaminating water, soil, air, and food, and they build up in people and the environment over time.

We don’t know a lot about the thousands of different PFAS because it takes years to do studies, and we haven’t known about them for that many years. But research so far has suggested that PFAS are associated with a host of biological changes, even at very low levels. PFAS exposure has been linked with many adverse health outcomes, such as decreased immune system function, thyroid disease, and kidney and testicular cancers.

The EPA recently set regulations for six PFAS chemicals, ones that we know are the easiest to measure and are associated with numerous health effects. Many people are researching PFAS, but industry is constantly altering the formulations for new and different applications, and so there’s no way to stop this train. But the EPA’s efforts are really good news.

Another issue that the EPA needs to address is revising the standard for arsenic in drinking water. We’ve known that arsenic is a poison for a really long time, and that’s actually what makes it so useful—we use it in chemotherapies, pesticides, and herbicides. It has a lot of other useful applications, like in paints and glassmaking. But arsenic has negative health effects across the board, including cardiovascular harms, liver damage, neurotoxicity, and reproductive toxicity.

The arsenic limit for drinking water—which was set in 2001 at 10 parts per billion—is probably an order of magnitude too high. It was looking like the EPA might propose lowering the arsenic standard in the next few years, but with the change in administration, that likelihood is looking dim. There’s a lot of resistance from industry and water utilities, but I think taking action on arsenic will be easier than regulating so many different types of PFAS, which is going to take a lot longer.

As for the EPA’s nitrate standard, it is dangerously high, and violations of the nitrate standard are the most common health-based violations of drinking water standards.

In general, the EPA is behind in keeping the drinking water standards up to date with the current scientific literature. Setting standards is a laborious process and, in addition, there is tremendous pushback from the “drinking water industry”—public water systems, which are often cities themselves, or semi-governmental agencies like the Massachusetts Water Resources Authority, which oversees water systems in the Boston metropolitan area. There are 50,000 active public water systems in the U.S., and there is a lot of complaining from those systems about the difficulty and expense of meeting stricter standards.

Q: What’s the evidence supporting those recommendations?

A: My colleagues and I wrote a 2023 review article about the exposure risks of a wide range of drinking water contaminants, including PFAS, arsenic, and more. In that article, we cited a number of studies linking these chemicals to health harms:

A 2023 meta-analysis of over a dozen different studies found that several types of PFAS may lower the body’s ability to produce antibodies after receiving vaccines, particularly for diphtheria, rubella, and tetanus.
A 2022 meta-analysis of over 100 rodent and human epidemiological studies identified a link between PFAS exposure and liver injury.
A 2013 study followed almost 4,000 individuals for around two decades, and found that higher arsenic levels in urine were associated with increased mortality from lung, prostate, and pancreatic cancers.
A 2015 meta-analysis of over a dozen studies identified a link between arsenic exposure and adverse pregnancy outcomes and infant mortality.
A 2021 study analyzed nationwide data collected by the Centers for Disease Control and Prevention, finding that an increased level of arsenic in urine was associated with heart disease mortality.
Q: What do you hope can be accomplished to improve drinking water quality in the next four years?

A: Addressing both PFAS and arsenic will be difficult and expensive, and also take a lot of political will. The Supreme Court has tied the EPA’s hands through decisions such as eliminating the Chevron deference, which called for deferring to federal agencies for their judgments where federal law is silent or unclear, and the 2023 Sackett v. EPA case, which limited the agency’s power to regulate wetlands and waterways. The EPA can’t just issue regulations, it has to get laws passed through Congress, which is much harder to do. It used to be that the courts would defer to the EPA, but now the agency is going to have to make a much stronger case for regulations.

Regarding lead, now that the Biden administration has finalized the new lead pipe rule the government needs to make sure that the rule is implemented and enforced.

We have to regain a commitment to protecting human health and the environment, and clean drinking water should be a top priority. We have a lot of hard work to do.

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Exposure to PFAS in drinking water linked to higher blood levels of these “forever” chemicals

First-of-its-kind study at ADLM 2025 lays the foundation for addressing public health threat

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CHICAGO — Breaking research presented today at ADLM 2025 (formerly the AACC Annual Scientific Meeting & Clinical Lab Expo) found that people who live in areas with higher levels of PFAS in their drinking water also have elevated blood levels of these manufactured chemicals. Highlighting why these so-called “forever chemicals” are a growing public-health concern, these findings provide support for policies encouraging more PFAS testing and treatment in public water systems.

“Drinking water is one of the most important routes for exposure to environmental contaminants, including PFAS,” said Dr. Wen Dui, a member of the research team from Quest Diagnostics that conducted the study. “This study was the first of its kind to apply the National Academies of Science, Engineering, and Medicine (NASEM) PFAS guidance to study correlation between PFAS in human bodies and drinking water in a large-scale clinical population.” 

First developed in the 1940s, PFAS, or per- and poly-fluoroalkyl substances, were designed to resist water, oil, grease, and heat, making them useful in numerous consumer products and across multiple industries. For example, PFAS can be found in non-stick cookware, waterproof clothing, and fast-food packaging, as well as in firefighting foams, aircraft components, medical devices, and construction materials. The substances can enter the public water supply when manufacturers release wastewater into nearby water sources, for example, or when PFAS in landfills leach into groundwater.

Scientists are concerned about possible health consequences of PFAS, which build up in people and the environment over time. For instance, NASEM found evidence of an association between PFAS and adult kidney cancer, decreased infant and fetal growth, abnormally high cholesterol, and a reduced antibody response. The NASEM guidance recommends that anyone with high blood levels of PFAS, defined as a summed total of more than 20 ng/mL of nine key PFAS, receive further testing and reduce their exposure.

“Several federal agencies, including the Centers for Disease Control and Prevention and NASEM, have worked together to summarize evidence, publish guidance, and encourage more clinical PFAS testing,” Dui said. “Quest developed and published a blood test for serum PFAS quantitation of the nine NASEM-recommended analytes to address the critical need for reliable PFAS measurement in clinical laboratories,” Dui said.

As one of its first steps, the team sought to establish the relationship between drinking water contaminated with PFAS and PFAS levels in people’s blood — which is what this new study accomplishes.

Since the U.S. Environmental Protection Agency monitors the amount of PFAS in public water systems, the researchers were able to pull information from previously collected blood samples to do a geographic comparison by exposure level. They evaluated blood samples taken from 771 individuals who lived in zip codes with high exposure to PFAS through their water and 788 people with low exposure to the substances, ensuring the two groups were otherwise comparable in their age and gender distribution.

They found that 7.1% of the people from zip codes with high-exposure to PFAS had elevated blood levels of PFAS (>20 ng/mL), versus only 2.8% of the people in the low-exposure group — a significant difference. Moreover, the estimated average of combined PFAS in the blood samples was significantly higher in the high-exposure group (9.2 ng/mL) versus the low-exposure group (6.1 ng/mL), as were mean blood levels of each individual PFAS studied.

“Our study found that a higher PFAS level in U.S. public drinking water supply corresponds to higher PFAS serum concentrations in exposed communities,” Dui said, adding that, as a next step, the company hopes to contribute to research on the correlation between PFAS exposure and health outcomes.

Session information

ADLM 2025 registration is free for members of the media. Reporters can register online here: https://xpressreg.net/register/adlm0725/media/landing.asp

Abstract B-281: Correlation between PFAS forever chemical concentrations in remnant serum and public drinking water will be presented during:

Scientific poster session
Wednesday, July 30
9:30 a.m. – 5 p.m. (presenting authors in attendance from 1:30 – 2:30 p.m.)

The session will take place in the Poster Hall on the Expo show floor of McCormick Place, Chicago.

About ADLM 2025

ADLM 2025 (formerly the AACC Annual Scientific Meeting & Clinical Lab Expo) offers 5 days packed with opportunities to learn about exciting science from July 27-31 in Chicago. Plenary sessions will explore urgent problems related to clinical artificial intelligence (AI) integration, fake medical news, and the pervasiveness of plastics, as well as tapping into the promise of genomics and microbiome medicine for personalized healthcare.

At the ADLM 2025 Clinical Lab Expo, more than 800 exhibitors will fill the show floor of the McCormick Place Convention Center in Chicago, with displays of the latest diagnostic technology, including but not limited to AI, point-of-care, and automation.

About the Association for Diagnostics & Laboratory Medicine (ADLM)

Dedicated to achieving better health for all through laboratory medicine, ADLM (formerly AACC) unites more than 70,000 clinical laboratory professionals, physicians, research scientists, and business leaders from 110 countries around the world. Our community is at the forefront of laboratory medicine’s diverse subdisciplines, including clinical chemistry, molecular diagnostics, mass spectrometry, clinical microbiology, and data science, and is comprised of individuals holding the spectrum of lab-related professional degrees, certifications, and credentials. Since 1948, ADLM has championed the advancement of laboratory medicine by fostering scientific collaboration, knowledge sharing, and the development of innovative solutions that enhance health outcomes. For more information, visit www.myadlm.org.

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https://myadlm.org/media/press-release-archive/2025/07-july/exposure-to-pfas-in-drinking-water-linked-to-higher-blood-levels-of-these-forever-chemicals?

Study links PFAS contamination of drinking water to a range of rare cancers

In the first study of its kind, researchers from the Keck School of Medicine of USC found an association between levels of manmade “forever chemicals” in drinking water and the incidence of certain digestive, endocrine, respiratory, and mouth and throat cancers.

Zara Abrams

Image shows water from faucet with the letters PFAS under a magnifying glass.
Image/Francesco Scatena, iStock

Communities exposed to drinking water contaminated with manufactured chemicals known as per- and polyfluoroalkyl substances (PFAS) experience up to a 33% higher incidence of certain cancers, according to new research from the Keck School of Medicine of USC.

The study, funded by the National Institutes of Health and just published in the Journal of Exposure Science and Environmental Epidemiology, is the first to examine cancer and PFAS contamination of drinking water in the U.S.

PFAS, which are used in consumer products such as furniture and food packaging, have been found in about 45% of drinking water supplies across the United States. Past research has linked the chemicals, which are slow to break down and accumulate in the body over time, to a range of health problems, including kidney, breast and testicular cancers.

To paint a more comprehensive picture of PFAS and cancer risk, Keck School of Medicine researchers conducted an ecological study, which uses large population-level datasets to identify patterns of exposure and associated risk. They found that between 2016 and 2021, counties across the U.S. with PFAS-contaminated drinking water had higher incidence of certain types of cancer, which differed by sex. Overall, PFAS in drinking water are estimated to contribute to more than 6,800 cancer cases each year, based on the most recent data from the U.S. Environmental Protection Agency (EPA).

“These findings allow us to draw an initial conclusion about the link between certain rare cancers and PFAS,” said Shiwen (Sherlock) Li, PhD, a postdoctoral researcher in the Department of Population and Public Health Sciences at the Keck School of Medicine and first author of the study. “This suggests that it’s worth researching each of these links in a more individualized and precise way.”

In addition to providing a roadmap for researchers, the findings underscore the importance of regulating PFAS. Starting in 2029, the EPA will police levels of six types of PFAS in drinking water, but stricter limits may ultimately be needed to protect public health, Li said.

The toll of PFAS 

To understand how PFAS contamination relates to cancer incidence, the researchers compared two exhaustive datasets—one covering all reported cancer cases and the other including all data on PFAS in drinking water data across the country. Data on cancer cases between 2016 and 2021 were obtained from the National Cancer Institute’s Surveillance, Epidemiology, and End Results Program, while data on PFAS levels in public drinking water (2013-2024) came from the EPA’s Unregulated Contaminant Monitoring Rule programs.

Li and his colleagues controlled for a number of factors that could influence cancer risk. At the individual level, these included age and sex; at the county level, they ruled out changes in cancer incidence due to socioeconomic status, smoking rates, obesity prevalence, urbanicity (how urban or rural an area is) and the presence of other pollutants.

The researchers then compared cancer incidence in each county to PFAS contamination in the drinking water, using the EPA’s recommended cutoffs for each type of PFAS. Counties where drinking water surpassed recommended maximum levels of PFAS had a higher incidence of digestive, endocrine, respiratory, and mouth and throat cancers. Increases in incidence ranged from slightly elevated at 2% to substantially elevated at 33% (the increased incidence of mouth and throat cancers linked to perfluorobutanesulfonic acid, or PFBS).

Males in counties with contaminated drinking water had a higher incidence of leukemia, as well as cancers of the urinary system, brain and soft tissues, compared to males living in areas with uncontaminated water. Females had a higher incidence of cancers in the thyroid, mouth and throat, and soft tissues. Based on the latest available EPA data, the researchers estimate that PFAS contamination of drinking water contributes to 6,864 cancer cases per year.

“When people hear that PFAS is associated with cancer, it’s hard to know how it’s relevant. By calculating the number of attributable cancer cases, we’re able to estimate how many people may be affected,” Li said, including inferring the personal and financial toll of these cases year after year.

Protecting public health 

These population-level findings reveal associations between PFAS and rare cancers that might otherwise go unnoticed. Next, individual-level studies are needed to determine whether the link is causal and to explore what biological mechanisms are involved.

On the regulation side, the results add to the mounting evidence that PFAS levels should be limited, and suggest that proposed changes may not go far enough.

“Certain PFAS that were less studied need to be monitored more, and regulators need to think about other PFAS that may not be strictly regulated yet,” Li said

The work is part of a collaboration between the Southern California Environmental Health Sciences Center, which is funded by the National Institute of Environmental Health Sciences, and the USC Norris Comprehensive Cancer Center at the Keck School of Medicine.

About this research 

In addition to Li, the study’s other authors are Lu Zhang, Jesse Goodrich, Rob McConnell, David Conti, Lida Chatzi and Max Aung from the Department of Population and Public Health Science, Keck School of Medicine of USC, University of Southern California; and Paulina Oliva from the Department of Economics, Dornsife College of Letters, Arts and Sciences, University of Southern California.

This work was supported by a pilot grant from the Southern California Environmental Health Sciences Center [P30ES007048] and the National Cancer Institute [5P30CA014089-47].

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Study links PFAS contamination of drinking water to a range of rare cancers

New EPA data shows 165M people exposed to ‘forever chemicals’ in U.S. drinking water

WASHINGTON – New data released by the Environmental Protection Agency shows an additional 6.5 million Americans have drinking water contaminated by the toxic “forever chemicals” known as PFAS. It brings the total number of people at risk of drinking this contaminated tap water to about 165 million across the U.S. 

That’s a 4% increase in the number of Americans with verified PFAS-polluted water in just the last few months. Exposure to PFAS is linked to cancer, reproductive harm, immune system damage and other serious health problems, even at low levels. 

“It is impossible to ignore the growing public health crisis of PFAS exposure. It’s detectable in nearly everyone and it’s found nearly everywhere, including the drinking water for a huge segment of the population,” said David Andrews, Ph.D., acting chief science officer at the Environmental Working Group.

“The documented extent of PFAS contamination of the country’s water supply highlights the enormous scale of contamination,” he added.  

The EPA’s new findings come from tests of the nation’s drinking water supply conducted as part of the Fifth Unregulated Contaminant Monitoring Rule, or UCMR 5, which requires U.S. water utilities to test drinking water for 29 individual PFAS compounds.

Protections under threat

In 2024, the EPA finalized first-time limits on six PFAS in drinking water, which help tackle forever chemicals contamination – but these standards are now at risk.

The EPA has said it will roll back limits on four PFAS in drinking water, leaving those chemicals unregulated. It plans to only retain standards for the  two most notorious chemicals, PFOA and PFOS. These maximum contaminant levels or MCLs, set enforceable standards for the amount of contaminants allowed in drinking water. 

Even with keeping the PFOA and PFOS MCLs in place, rolling back the four other limits will make it harder to hold polluters responsible and ensure clean drinking water.

In addition, the EPA’s plan to reverse the four science-based MCLs likely contradicts an anti-backsliding provision in the Safe Drinking Water Act. That law requires any revision to a federal drinking water standard “maintain, or provide for greater, protection of the health of persons.”

“It’s worrying to see the EPA renege on its commitments to making America cleaner and safer, especially as it ignores its own guidelines to do so,” said Melanie Benesh, EWG’s vice president for government affairs.

Widespread PFAS pollution 

The Trump administration’s PFAS standards rollback could grant polluters unchecked freedom to release toxic forever chemicals into U.S. waterways, endangering millions of Americans.

EWG estimates nearly 30,000 industrial polluters could be discharging PFAS into the environment, including into sources of drinking water. Restrictions on industrial discharges would lower the amount of PFAS ending up in drinking water sources.

“Addressing the problem means going to the source. For PFAS, that’s industrial sites, chemical plants and the unnecessary use of these chemicals in consumer products,” said Andrews. 

Health risks of PFAS exposure

PFAS are toxic at extremely low levels. They are known as forever chemicals because once released into the environment, they do not break down and can build up in the body. The Centers for Disease Control and Prevention has detected PFAS in the blood of 99 percent of Americans, including newborn babies. 

Very low doses of PFAS have been linked to suppression of the immune system. Studies show exposure to PFAS can also increase the risk of cancer, harm fetal development and reduce vaccine effectiveness. 

For over 30 years, EWG has been dedicated to safeguarding families from harmful environmental exposures, holding polluters accountable and advocating for clean, safe water.

“Clean water should be the baseline,” Andrews said, “The burden shouldn’t fall on consumers to make their water PFAS-free. While there are water filters that can help, making water safer begins with ending the unnecessary use of PFAS and holding polluters accountable for cleanup.” 

For people who know of or suspect the presence of PFAS in their tap water, a home filtration system is the most efficient way to reduce exposure. Reverse osmosis and activated carbon water filters can be extremely effective at removing PFAS. 

EWG researchers tested the performance of 10 popular water filters to evaluate how well each reduced PFAS levels detected in home tap water. 

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The Environmental Working Group is a nonprofit, non-partisan organization that empowers people to live healthier lives in a healthier environment. Through research, advocacy and unique education tools, EWG drives consumer choice and civic action.

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https://www.ewg.org/news-insights/news-release/2025/06/new-epa-data-shows-165m-people-exposed-forever-chemicals-us?

Yale Experts Explain PFAS ‘Forever Chemicals’

Illustration of a frying pan and spatula

PFAS, also known as “forever chemicals,” have emerged as a serious environmental and public health threat due to their persistence and widespread contamination. These man-made chemicals, widely utilized in consumer and industrial products since World War II, are now linked to alarming levels of contamination in drinking water supplies and health risks ranging from cancers to liver toxicity to reduced fertility. 

Following decades of litigation, the U.S. Environmental Protection Agency in 2024 finally set legally enforceable levels for six PFAS chemicals in drinking water, requiring public water systems to monitor for the substances, report findings to customers, and take steps to reduce contamination. However, those regulations were partially rolled back in May 2025. 

In this Q&A, two Yale experts delve into the challenges posed by PFAS and potential solutions for reducing exposure and contamination. Vasilis Vasiliou is Department Chair and Susan Dwight Bliss Professor of Epidemiology at Yale School of Public Health (YSPH). Robert Bilott is an environmental attorney and serves as a lecturer with the YSPH Department of Environmental Health Sciences. Bilott’s story and landmark case against chemical giant DuPont were recounted in his book, “Exposure: Poisoned Water, Corporate Greed, and One Lawyer’s Twenty-Year Battle Against DuPont,” and were the basis for the 2019 motion picture “Dark Waters,” starring Mark Ruffalo. 

This interview was edited and condensed for clarity. 

What are PFAS? 

BILOTT: PFAS stands for per- and polyfluoroalkyl substances. They are a completely man-made family of chemicals created around the time of World War II. These chemicals, formed by artificially connecting carbon and fluorine, are known for their strength, stain resistance, grease protection, and water resistance. They are used in a wide variety of products, and there are now estimates of up to 14,000 different PFAS compounds. 

Why are PFAS called ‘forever chemicals?’ 

VASILIOU: PFAS are often called ‘forever chemicals’ because they contain an exceptionally strong carbon-fluorine bond, which makes them highly resistant to breakdown. As a result, they persist in the environment for decades or longer—in water, soil, and even living organisms. Their environmental and biological persistence means they can accumulate over time, raising long-term concerns for ecosystems and public health. 

What consumer or industrial products contain PFAS? 

BILOTT: PFAS have been used in an incredible array of consumer and commercial products since the 1940s. Common products containing PFAS include non-stick cookware, carpeting, clothing, fast food wrappers and packaging, computer chips, toilet paper, and waterproof cosmetics. Keywords like stain-resistant, waterproof, grease-resistant, and non-stick often indicate the presence of PFAS. These chemicals were not listed on ingredient lists or labels, and many companies were unaware they were using them. 

What are the known health risks associated with PFAS? 

VASILIOU: PFAS are linked to various cancers such as kidney, testicular, and liver cancer, as well as liver toxicity. There is a rising incidence of early-onset cancers, like colon and liver cancer, in younger individuals, potentially due to developmental exposure. Developmental and reproductive effects of PFAS include low birth weight, accelerated puberty, reduced fertility, and pregnancy-induced hypertension, with possible epigenetic changes that might contribute to early-onset cancers. PFAS also impair the immune system, reducing vaccine effectiveness and potentially increasing susceptibility to infections like COVID-19. Additionally, PFAS exposure is linked to various metabolic effects such as obesity, type 2 diabetes, cardiovascular disease, reduced kidney function, high cholesterol, colitis, and neurodegenerative issues in children. 

By some estimates, 90% of drinking water in the U.S. contains PFAS. How did that happen? 

BILOTT: PFAS contamination in drinking water primarily comes from aqueous film-forming foam, or AFFF—the firefighting foam that was developed during the Vietnam War to extinguish petroleum-based fires. This foam contains high concentrations of C-8 PFAS chemicals known as PFOA and PFOS that have been widely used by military organizations, airports, and fire stations globally since the 1960s. The people buying and using it were not informed about its PFAS content and were misled about its safety, which led to widespread environmental contamination. 

Has a safe level for PFAS chemicals been identified? 

BILOTT: No one has identified a safe level of PFAS chemicals. Companies like 3M and DuPont set internal safety guidelines for their employees decades ago, but this information was withheld from government agencies and scientists until much later. Studies have revealed that PFAS are persistent, bioaccumulative, and toxic, affecting multiple organ systems and potentially reducing vaccine effectiveness. The EPA has set very low drinking water standards, aiming for no more than four parts per trillion and ideally zero for PFOA and PFOS, which are now recognized as human carcinogens. 

VASILIOU: PFAS chemicals are not metabolized by the body, unlike many other environmental contaminants. Because they resist breakdown and are only slowly excreted, they accumulate in human tissues—especially in the blood, liver, and kidneys—over time. This bioaccumulation contributes to a range of toxic effects, including immunotoxicity, endocrine disruption, and increased risk of kidney and testicular cancer. Given their extreme persistence and potential for harm even at very low levels, efforts to establish safe exposure limits increasingly aim toward zero. 

Can the human body repair damage caused by PFAS? 

VASILIOU: The human body has some ability to repair tissue damage, but with PFAS, this process is complicated by the chemicals’ persistence. PFAS remain in the body for years and can interfere with normal repair mechanisms by promoting inflammation, oxidative stress, and immune dysfunction. Even if some tissues, like the liver, can regenerate, ongoing internal exposure means that damage may continue, making full recovery difficult—especially with chronic or high-level exposures.

Are any PFAS chemicals regulated? 

BILOTT: In 2024, the first federal nationwide regulations for PFAS chemicals were adopted by the EPA, setting drinking water standards and declaring two C-8 PFAS as hazardous under federal Superfund law. The process took decades, with companies pushing back and fighting regulation in courts. States like New Jersey, Minnesota, and Connecticut have also moved forward with regulations, which are facing legal challenges from manufacturers. In Europe, proposed global bans on PFAS face significant opposition due to economic impacts.

What technologies exist to remove PFAS from drinking water? 

VASILIOU: Activated carbon and reverse osmosis are the primary technologies to remove PFAS, though reverse osmosis is very expensive for individual homes. Yale engineers are working on innovative solutions, such as membranes and methods to break down PFAS chemicals.

Who is going to pay for cleaning up PFAS contamination? 

BILOTT: Our law firm represents hundreds of cities seeking compensation from companies like 3M and DuPont, who created the chemicals. These cases are part of the aqueous film-forming foam (AFFF) multidistrict litigation in South Carolina. Recently, significant settlements totaling over $14 billion from companies like 3M, DuPont, BASF, and Tyco have been reached to help public water systems clean up PFAS. The federal government has allocated $10 billion for this purpose but that is taxpayer money. We are working to ensure the responsible companies pay for the cleanup. 

How does someone know if PFAS is present in their drinking water or consumer products? 

BILOTT: It’s not always easy. For public water systems, sampling is starting to be required and information may be available in quarterly reports to customers. But many districts haven’t started testing yet. The Environmental Working Group created an interactive map showing where testing has occurred and what the levels are. For consumer products, there’s a lot less information. PFAS were not listed on ingredient labels or material safety data sheets, and even manufacturers might not have known they were using PFAS. Some groups are now testing products for PFAS, and products labeled with buzzwords like waterproof, stain-resistant, non-stick, and grease-proof might contain PFAS. Consumer demand has led some companies to commit to PFAS-free products, but definitions and detection levels vary so that is causing mass confusion in the market. 

What can the average person do about the PFAS problem? 

VASILIOU: Individuals can reduce their PFAS exposure by avoiding products such as older non-stick cookware, water-resistant clothing, stain-proof textiles, and certain cosmetics that may contain PFAS. It’s also important to be informed about your drinking water—use certified filters that are effective against PFAS and consult local or state resources for water quality information, including bottled water when available. Beyond personal choices, civic engagement plays a powerful role. Raising awareness, supporting legislation, and demanding transparency from manufacturers and regulators can drive meaningful, large-scale change 

BILOTT: An individual can make a huge difference by standing up, speaking out, and demanding change. It may take a while, but as you see in the story of “Dark Waters,” individuals speaking out are having a huge impact. Laws are being proposed and passed to restrict these chemicals. Some of the biggest companies on the planet are now committing to getting out of PFAS. That only happened by individuals saying ‘we don’t want this.’ 

What is Yale doing? 

Yale is committed to making the university a healthy and productive place to live, work, and study. We are reducing the amount of harmful chemicals on campus through healthy furniture standards to reduce the amount of chemicals of concern in the materials we purchase to furnish our buildings. The Yale School of Public Health is leading groundbreaking research into the human health impacts of PFAS, analyzing their role in cancer cell migration, liver damage, and pregnancy loss. The Yale School of Engineering and Applied Sciences is developing technologies to separate and destroy PFAS at water treatment facilities and other locations.

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https://sustainability.yale.edu/explainers/yale-experts-explain-pfas-forever-chemicals?

EPA Announces It Will Keep Maximum Contaminant Levels for PFOA, PFOS

EPA intends to provide regulatory flexibility and holistically address these contaminants in drinking water 

Contact Information

EPA Press Office (press@epa.gov)

WASHINGTON – U.S. Environmental Protection Agency (EPA) Administrator Lee Zeldin announced the agency will keep the current National Primary Drinking Water Regulations (NPDWR) for perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), which set nationwide limits for these “forever chemicals” in drinking water. The agency is committed to addressing Per- and Polyfluoroalkyl substances (PFAS) in drinking water while following the law and ensuring that regulatory compliance is achievable for drinking water systems. 

“The work to protect Americans from PFAS in drinking water started under the first Trump Administration and will continue under my leadership,” said EPA Administrator Zeldin. “We are on a path to uphold the agency’s nationwide standards to protect Americans from PFOA and PFOS in their water. At the same time, we will work to provide common-sense flexibility in the form of additional time for compliance. This will support water systems across the country, including small systems in rural communities, as they work to address these contaminants. EPA will also continue to use its regulatory and enforcement tools to hold polluters accountable.” 

As part of this action, EPA is announcing its intent to extend compliance deadlines for PFOA and PFOS, establish a federal exemption framework, and initiate enhanced outreach to water systems, especially in rural and small communities, through EPA’s new PFAS OUTreach Initiative (PFAS OUT). This action would help address the most significant compliance challenges EPA has heard from public water systems, members of Congress, and other stakeholders, while supporting actions to protect the American people from certain PFAS in drinking water.  

Paired with effluent limitations guidelines (ELGs) for PFAS and other tools to ensure that polluters are held responsible, EPA’s actions are designed to reduce the burden on drinking water systems and the cost of water bills, all while continuing to protect public health and ensure that the agency is following the law in establishing impactful regulations such as these. 

EPA is also announcing its intent to rescind the regulations and reconsider the regulatory determinations for PFHxS, PFNA, HFPO-DA (commonly known as GenX), and the Hazard Index mixture of these three plus PFBS to ensure that the determinations and any resulting drinking water regulation follow the legal process laid out in the Safe Drinking Water Act. 

Regulatory Protection with Flexibility and Cost Savings   

On April 10, 2024, EPA announced the final National Primary Drinking Water Regulation, including standards for PFOA and PFOS. At that time, EPA established legally enforceable levels for these PFAS in drinking water and gave public water systems until 2029 to comply with the Maximum Contaminant Levels (MCLs). 

To allow drinking water systems more time to develop plans for addressing PFOA and PFOS where they are found and implement solutions, EPA plans to develop a rulemaking to provide additional time for compliance, including a proposal to extend the compliance date to 2031. EPA plans to issue a proposed rule this fall and finalize this rule in the Spring of 2026. Aligned with the agency’s intent to provide additional compliance time for water systems, EPA encourages states seeking primacy for implementing the PFAS drinking water regulation to request additional time from EPA to develop their applications. At the same time, EPA will support the U.S. Department of Justice in defending ongoing legal challenges to the PFAS National Primary Drinking Water Regulation with respect to PFOA and PFOS.  

“EPA has done the right thing for rural and small communities by delaying implementation of the PFAS rule. This commonsense decision provides the additional time that water system managers need to identify affordable treatment technologies and make sure they are on a sustainable path to compliance. NRWA greatly appreciates this reasonable and flexible approach, and we look forward to partnering with the agency’s PFAS OUTreach Initiative to help ensure water systems have the resources and support they need,” said National Rural Water Association CEO Matthew Holmes.  

“ASDWA supports EPA’s proposed approach to the PFAS regulation to extend the compliance date for systems by an additional two years. With the current compliance date of 2029, states and water systems are struggling with the timeframes to complete the pilot testing, development of construction plans, and building the necessary treatment improvements. EPA’s proposed extension of the compliance date and increased technical assistance will address the number of systems that would be out of compliance in 2029 due to not being able complete all of these tasks on time,” said Association of State Drinking Water Administrators Executive Director Alan Roberson. 

Enhancing Communication and Outreach  

To enhance engagement on addressing PFAS, EPA will launch PFAS OUT to connect with every public water utility known to need capital improvements to address PFAS in their systems, including those EPA has identified as having PFOA and PFOS levels above EPA’s MCL. EPA will share resources, tools, funding, and technical assistance to help utilities meet the federal drinking water standards. PFAS OUT will ensure that no community is left behind as we work to protect public health and bring utilities into compliance with federal drinking water standards. PFAS OUT will engage utilities, technical assistance providers and local, State, Tribal, and Territorial leaders to develop effective, practical solutions where they are needed most. 

EPA will continue to offer free water technical assistance (WaterTA) that provides services to water systems to improve their drinking water and help communities access available funding. EPA’s WaterTA initiatives work with water systems nationwide to identify affordable solutions to assess and address PFAS, including PFOA and PFOS. Services offered to utilities include water quality testing, development of technical plans, operator training support, designing public engagement and outreach strategies, and support for accessing federal funding opportunities.   

Holding Polluters Accountable  

Drinking water systems are passive receivers of PFOA and PFOS. Polluters can contaminate the surface waters or aquifers that these systems rely on to provide the drinking water to their communities. As announced by Administrator Zeldin, EPA intends to take a number of actions to reduce the prevalence of PFAS in the environment, including in sources of drinking water. Progress reducing concentrations of PFAS in drinking water sources can substantially reduce the cost burden for water systems and reduce the cost of living for the communities they serve. 

A Record of Leadership   

Administrator Zeldin’s leadership on PFAS dates back to his time in Congress, where he was a founding member of the PFAS Congressional Taskforce and a strong supporter of the PFAS Action Act, legislation to provide funding to support local communities cleaning up PFAS-contaminated water systems. He was, and remains, a staunch advocate for protecting Long Islanders and all Americans from contaminated drinking water.    

In the process of developing and taking action on a number of these items, Administrator Zeldin personally heard from members of Congress on passive receiver issues where local water utilities will foot the bill for contamination and pass those costs onto consumers. This mindset and the need for a polluter pays model has guided a lot of the work to be done at EPA in the future.  

Background    

On April 28, 2025, Administrator Zeldin announced a long list of actions to combat PFAS contamination that included in part the designation of an agency lead for PFAS, the development of ELGs for certain PFAS to reduce discharges to waterways including upstream of drinking water systems, and initiatives to engage with Congress and industry to establish a clear liability framework that ensures passive receivers and consumers are protected. This list is the first, not the last, of all decisions and actions EPA will be taking to address PFAS over the course of the Trump Administration. There will be more to come in the future across EPA’s program offices to help communities impacted by PFAS contamination.  

During President Trump’s first term, EPA convened a two-day National Leadership Summit on PFAS in Washington, D.C. that brought together more than 200 federal, state, and local leaders from across the country to discuss steps to address PFAS. Following the Summit, the agency hosted a series of visits during the summer of 2018 in communities directly impacted by PFAS. EPA interacted with more than 1,000 Americans during community engagement events in Exeter, New Hampshire, Horsham, Pennsylvania, Colorado Springs, Colorado, Fayetteville, North Carolina, and Leavenworth, Kansas, as well as through a roundtable in Kalamazoo, Michigan, and events with tribal representatives in Spokane, Washington.  

In 2019, the Trump EPA announced the PFAS Action Plan. This historic Plan responded to extensive public interest and input the agency received and represented the first time EPA built a multi-media, multi-program, national communication and research plan to address an emerging environmental challenge like PFAS. EPA’s Action Plan identified both short-term solutions for addressing these chemicals and long-term strategies that will help provide the tools and technologies states, tribes, and local communities need to provide clean and safe drinking water to their residents and to address PFAS at the source—even before it gets into the water. 

EPA supports water systems in reducing PFAS and emerging contaminants (EC) in drinking water through a range of funding resources. Federal funding opportunities include the Drinking Water State Revolving Fund (DWSRF) program, the EC Small or Disadvantaged Communities (EC-SDC) grant program, and funding resources, like EPA’s Water Infrastructure Finance and Innovation Act (WIFIA) program, that can be leveraged to provide supplemental, flexible, low-cost credit assistance to public and private borrowers. 

For information about the PFAS Rule, visit Final PFAS National Primary Drinking Water Regulation and Per- and Polyfluoroalkyl Substances (PFAS) NPDWR Implementation. For more information about PFAS Technical Assistance, visit EPA Water Technical Assistance. You can also Request EPA WaterTA services for your community.  

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https://www.epa.gov/newsreleases/epa-announces-it-will-keep-maximum-contaminant-levels-pfoa-pfos?

Troubled waters? The future of drinking water in the U.S.

From fluoride to “forever chemicals,” drinking water has been in the spotlight this year. In a Q&A, Yale epidemiologist Nicole Deziel discusses the water we drink today — and what’s on tap for the future.

Aug 13, 2025

7 min read

By Meg Dalton

(Illustration by Michael S. Helfenbein)

Woman drinking water from a glass

Listen to this story

8:33

In 1945, Grand Rapids, Michigan, made history — as the first city in the world to add small amounts of fluoride to its public water supply. At the time, studies showed communities with higher levels of natural fluoride in water had better dental health. Water fluoridation is now practiced in about 25 countries around the world, including Spain, Malaysia, and the United States. In the U.S., approximately 63% of the population drinks fluoridated water.

Low levels of fluoride, a naturally occurring mineral, can be found in many sources of drinking water due to natural processes like the weathering of rocks and human activities like manufacturing. However, there’s growing debate over whether additional fluoride should be introduced to drinking water. This year, states including Utah and Florida have banned the use of fluoride in public water systems, and federal officials have called for more states to follow suit.

Nicole Deziel is an associate professor of epidemiology (environmental health sciences) and co-director of the Yale Center for Perinatal, Pediatric and Environmental Epidemiology at the Yale School of Public Health. In an interview, she explains the benefits and risks of fluoride, how “forever chemicals” and climate change impact water quality, and how we can monitor the water we drink.

Nicole Deziel
Nicole Deziel

The interview has been edited for length and clarity.

What are the benefits of fluoride? Are there any potential risks?

Nicole Deziel: Fluoride can strengthen our bones and teeth enamel, and the strengthening of the enamel prevents cavities. But too much of it can damage our bones and enamel in a process called fluorosis, and it can potentially have neurological effects as well. Fluoridation of the public water supply can help address disparities in dental insurance and access to dental care.

Finding the right amount where the benefits outweigh the risks is key. The U.S. Public Health Service recommends a fluoride concentration of 0.7 mg/L [parts per million] in drinking water. The World Health Organization recommends a limit of 1.5 mg/L, while the U.S. Environmental Protection Agency sets a limit of 4 mg/L. Newer evidence of more subtle neurological effects is prompting reexamination of these target levels and limits.

Why are we seeing some states ban the use of fluoride in public water systems? Why are some people suspicious of it?

Deziel: There’s a long history of controversy about fluoride, including urban legends and conspiracy theories. For some people, it may seem counterintuitive to add a chemical that may have some toxic properties to make our water safer. However, we do this with chlorine as well. Chlorine is toxic at high levels and can form harmful byproducts, but we add it to drinking water to disinfect it and kill bacteria and pathogens to make our water safe to drink. We’re often doing these kinds of tradeoffs in environmental health and public health. In addition, misinformation and distrust of science could all be contributing to us revisiting this [the fluoridation of water]. 

Finding the right amount [of fluoride] where the benefits outweigh the risks is key.

Nicole Deziel

However, there’s been some new data that should prompt us to reexamine fluoride. There have been a few recent studies that have shown that fluoride exposure is linked to lower IQ levels in children where fluoride levels are above some of the target levels. Some in the dental community have raised concerns about how the data in those studies are being interpreted. Given these concerns, it is important that experts across disciplines collectively re-examine the latest evidence on fluoride’s risks and benefits to ensure the public and policymakers receive clear, evidence-based guidance.

Let’s move from fluoride to so-called “forever chemicals,” also known as PFAS. What are PFAS, and why are they called “forever chemicals”?

Deziel: PFAS, or per- and polyfluoroalkyl substances, are commonly referred to as “forever chemicals” due to their persistence in the environment as well as human bodies. They’re molecules that have chains of carbon and fluorine, and the carbon-fluorine bond is the strongest chemical bond known.

Their properties have made PFAS very desirable in many consumer products like Teflon pans, stain-resistant and water-resistant clothing and textiles, food packaging, and more. They’re also in firefighting foam.

According to some estimates, 90% of drinking water in the U.S. contains PFAS. How did happen, and what impact do PFAS have on our health?

Deziel: This happens for a few reasons, such as improper disposal of PFAS at manufacturing sites and the use of firefighting foams at airports and military bases. But PFAS are also in household products, many of which can go down the drain and be introduced into our environment.

PFAS have been linked to a variety of adverse health problems, including endocrine disruption, cancer, reproductive effects, decreased effects on our immune system, decreased efficacy of vaccines, and more.

Last year, the U.S. set the first-ever national limits on PFAS. Now, some of those regulations are being delayed or reconsidered. How are limits set for contaminants like PFAS?

Deziel: The Environmental Protection Agency sets maximum contaminant levels for drinking water under the Safe Drinking Water Act. When they set them, they’re allowed to consider not just public health but technological or economic feasibility. It took about 20 years just to get the PFAS standards passed, even though we’ve known about these issues for decades. This is a very slow and inefficient process, and the standards are not keeping pace with the science. So, it’s frustrating that the few new standards set may not even move forward.

In recent years, we’ve also seen several extreme weather events, from wildfires and floods to intense heat and droughts. How does climate change threaten the safety of our drinking water?

Deziel: Climate change can impact our drinking water in many ways. First, increasing intense droughts can affect our water supplies and lead to water scarcity. With wildfires, we often focus on the smoke and the immediate damage, but once the fires have been addressed, there are concerns about all the fire-retardant chemicals that are deposited into our soils and waterways. Plus, wildfires require a lot of water. Rising sea levels can create saltwater intrusion into freshwater sources. Floods and storms can release chemicals into our waterways and impact our water infrastructure overall. So there are many ways our changing climate and extreme weather can affect drinking water.

What can people like you and me do to monitor — and even improve — the quality of the water we drink?

Deziel: In public health, we talk about a hierarchy of controls. So, the best would be to have evidence-based drinking water standards that reflect the best science, and that would be because not everybody has the time and resources to research different strategies or purchase different filters.

However, if someone wanted to reduce their exposures to chemicals, there are several different filtering devices that are available. The most common is the charcoal, or activated carbon, filter. These can remove some chemicals including chlorine, some metals, some organic contaminants, and some but not all PFAS. They can be installed for the whole house, under the sink, or directly on the faucet. Reverse osmosis filters, which push water through a special membrane, are more effective at removing a much wider range of chemicals, but they’re more expensive. Countertop and pitcher-style filters are other options. They use gravity to pass water through a carbon cartridge. They’re generally more affordable, and while they don’t remove as many contaminants as in-line systems, they offer some protection and may be a good starting point for some households.

People may be tempted to turn to bottled water. However, many brands of bottled water are just tap water that’s been run through extra purification steps (spring water and mineral water are exceptions). This additional treatment can mean the water is very clean, but bottled water comes with significant downsides. In the U.S., only a tiny fraction of the millions of plastic bottles we use actually get recycled, with most polluting streets, rivers, and oceans. Producing those bottles uses petroleum and releases greenhouse gases, adding to climate change. Moreover, single-use plastic bottles can release endocrine-disrupting chemicals called phthalates as well as tiny plastic particles known as microplastics, especially if left in sunlight and heat.

Media Contact

Fred Mamoun

fred.mamoun@yale.edu203-436-2643

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https://news.yale.edu/2025/08/13/troubled-waters-future-drinking-water-us?

Investigators

Portable tests could detect “forever chemicals” in your home’s drinking water

By Tara Molina

We know how important clean water is, but tricky chemicals that get into our water can be hard to detect, posing dangers to our water systems and our health ­– until now.

Researchers with the University of Chicago have teamed up with Argonne National Labs in Lemont to detect the smallest chemicals in our water in an effort to make it safer and healthier for all.

PFAS, or per- and polyfluoroalkyl substances, are better known as “forever chemicals.” They’re man-made compounds that are found in places like fast food packaging, firefighters’ foams and other places. They’re long-lasting chemicals and do not naturally degrade, instead accumulating in the environment and our bodies over time, which is why the Environmental Protection Agency issued regulations on them last year.

Until recently, they were somewhat difficult to detect in drinking water, but labs like Argonne are making gains.

“It affects essentially all of us, and it is, in fact, dangerous,” Argonne’s Seth Darling said. “They’re really toxic to humans. They’ve been linked to cancer, they’ve been linked to reproductive issues, thyroid problems, all kinds of health issues.”

Darling is working alongside Junhong Chen, with UChicago’s Pritzker School of Molecular Engineering. They’re building a first-of-its-kind sensor that can detect PFAS in water.

“The work we are doing here is really important, because now we have a way to be able to measure this PFAS,” Chen said. “Almost the only way to measure for PFAS is to take the water sample and send it to a high-end analytical laboratory for the analysis.”

Darling says that, because the chemicals are dangerous even at low concentrations, you need a technique that can test for extremely low levels. The sensor they’re behind can detect down to what would equate to one grain of sand in an Olympic-sized swimming pool, or 250 parts per quadrillion.

Typically, this level of inspection would require intensive and expensive lab testing. Their goal is to make these tests accessible for anyone to make sure their water is safe, directly from their home.

“What’s important here is developing new ways,” Darling said, “low-cost, fast ways to determine: Is there PFAS in your water and, if so, how much?”

Other universities in the Chicago area have also delved in to research PFAS. Back in the spring, Northwestern University professor of chemistry SonBinh Nguyen and professor of engineering Tim Wei developed a graphene oxide solution that is water- and oil-resistant and could be a replacement for PFAS in items such as takeout coffee cups.

Adam Harrington contributed to this report.

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https://www.cbsnews.com/chicago/news/chicago-researchers-portable-tests-forever-chemicals-drinking-water/?intcid=CNM-00-10abd1h