PFAS in pregnant women’s drinking water puts their babies at higher risk, study finds

Derek Lemoine, University of Arizona; Ashley Langer, University of Arizona, and Bo Guo, University of Arizona When pregnant women drink water that comes from wells downstream of sites contaminated with PFAS, known as “forever chemicals,” the risks to their babies’ health substantially increase, a new study found. These risks include the chance of low birth weight, preterm birth and infant mortality. Even more troubling, our team of economic researchers and hydrologists found that PFAS exposure increases the likelihood of extremely low-weight and extremely preterm births, which are strongly associated with lifelong health challenges.

What wells showed us about PFAS risks

PFAS, or perfluoroalkyl and polyfluoroalkyl substances, have captured the attention of the public and regulators in recent years for good reason. These man-made compounds persist in the environment, accumulate in human bodies and may cause harm even at extremely low concentrations. Most current knowledge about the reproductive effects of PFAS comes from laboratory studies on animals such as rats, or from correlations between PFAS levels in human blood and health outcomes. Both approaches have important limitations. Rats and humans have different bodies, exposures and living conditions. And independent factors, such as kidney functioning, may in some cases be the true drivers of health problems. We wanted to learn about the effects of PFAS on real-world human lives in a way that comes as close as possible to a randomized experiment. Intentionally exposing people to PFAS would be unethical, but the environment gave us a natural experiment of its own. We looked at the locations of wells that supply New Hampshire residents with drinking water and how those locations related to birth outcomes. We collected data on all births in the state from 2010 to 2019 and zoomed in on the 11,539 births that occurred within 3.1 miles (5 kilometers) of a site known to be contaminated with PFAS and where the mothers were served by public water systems. Some contamination came from industries, other from landfills or firefighting activities.

PFAS from contaminated sites slowly migrate down through soil into groundwater, where they move downstream with the groundwater’s flow. This created a simple but powerful contrast: pregnant women whose homes received water from wells that were downstream, in groundwater terms, from the PFAS source were likely to have been exposed to PFAS from the contaminated site, but those who received water from wells that were upstream of those sites should not have been exposed. Using outside data on PFAS testing, we confirmed that PFAS levels were indeed greater in “downstream” wells than in “upstream” wells. The locations of utilities’ drinking water wells are sensitive data that are not publicly available, so the women likely would not have known whether they were exposed. Prior to the state beginning to test for PFAS in 2016, they may not have even known the nearby site had PFAS.

PFAS connections to the riskiest births

We found what we believe is clear evidence of harm from PFAS exposure. Women who received water from wells downstream of PFAS-contaminated sites had on average a 43% greater chance of having a low-weight baby, defined as under 5.5 pounds (2,500 grams) at birth, than those receiving water from upstream wells with no other PFAS sources nearby. Those downstream had a 20% greater chance of a preterm birth, defined as before 37 weeks, and a 191% greater chance of the infant not surviving its first year. Per 100,000 births, this works out to 2,639 additional low-weight births, 1,475 additional preterm births and 611 additional deaths in the first year of life. Looking at the cases with the lowest birth weights and earliest preterm births, we found that the women receiving water from wells downstream from PFAS sources had a 180% greater chance of a birth under 2.2 pounds (1,000 grams) and a 168% greater chance of a birth before 28 weeks than those with upstream wells. Per 100,000 births, that’s about 607 additional extremely low-weight births and 466 additional extremely preterm births.

PFAS contamination is costly

When considering regulations to control PFAS, it helps to express the benefits of PFAS cleanup in monetary terms to compare them to the costs of cleanup. Researchers use various methods to put a dollar value on the cost of low-weight and preterm births based on their higher medical bills, lower subsequent health and decreased lifetime earnings. We used the New Hampshire data and locations of PFAS-contaminated sites in 11 other states with detailed PFAS testing to estimate costs from PFAS exposure nationwide related to low birth weight, preterm births and infant mortality. The results are eye-opening. We estimate that the effects of PFAS on each year’s low-weight births cost society about US$7.8 billion over the lifetimes of those babies, with more babies born every year. We found the effects of PFAS on preterm births and infant mortality cost the U.S. about $5.6 billion over the lifetimes of those babies born each year, with some of these costs overlapping with the costs associated with low-weight births. An analysis produced for the American Water Works Association estimated that removing PFAS from drinking water to meet the EPA’s PFAS limits would cost utilities alone $3.8 billion on an annual basis. These costs could ultimately fall on water customers, but the broader public also bears much of the cost of harm to fetuses. We believe that just the reproductive health benefits of protecting water systems from PFAS contamination could justify the EPA’s rule.

Treating PFAS

There is still much to learn about the risks from PFAS and how to avoid harm. We studied the health effects of PFOA and PFOS, two “long-chain” species of PFAS that were the most widely used types in the U.S. They are no longer produced in the U.S., but they are still present in soil and groundwater. Future work could focus on newer, “short-chain” PFAS, which may have different health impacts.

PFAS are in many types of products, and there are many routes for exposure, including through food. Effective treatment to remove PFAS from water is an area of ongoing research, but the long-chain PFAS we studied can be removed from water with activated carbon filters, either at the utility level or inside one’s home. Our results indicate that pregnant women have special reason to be concerned about exposure to long-chain PFAS through drinking water. If pregnant women suspect their drinking water may contain PFAS, we believe they should strongly consider installing water filters that can remove PFAS and then replacing those filters on a regular schedule. Derek Lemoine, Professor of Economics, University of Arizona; Ashley Langer, Professor of Economics, University of Arizona, and Bo Guo, Associate Professor of Hydrology, University of Arizona This article is republished from The Conversation under a Creative Commons license. Read the original article.

Most normal matter in the universe isn’t found in planets, stars or galaxies – an astronomer explains where it’s distributed

Chris Impey, University of Arizona If you look across space with a telescope, you’ll see countless galaxies, most of which host large central black holes, billions of stars and their attendant planets. The universe teems with huge, spectacular objects, and it might seem like these massive objects should hold most of the universe’s matter. But the Big Bang theory predicts that about 5% of the universe’s contents should be atoms made of protons, neutrons and electrons. Most of those atoms cannot be found in stars and galaxies – a discrepancy that has puzzled astronomers. If not in visible stars and galaxies, the most likely hiding place for the matter is in the dark space between galaxies. While space is often referred to as a vacuum, it isn’t completely empty. Individual particles and atoms are dispersed throughout the space between stars and galaxies, forming a dark, filamentary network called the “cosmic web.” Throughout my career as an astronomer, I’ve studied this cosmic web, and I know how difficult it is to account for the matter spread throughout space. In a study published in June 2025, a team of scientists used a unique radio technique to complete the census of normal matter in the universe.

The census of normal matter

The most obvious place to look for normal matter is in the form of stars. Gravity gathers stars together into galaxies, and astronomers can count galaxies throughout the observable universe. The census comes to several hundred billion galaxies, each made of several hundred billion stars. The numbers are uncertain because many stars lurk outside of galaxies. That’s an estimated 10²³ stars in the universe, or hundreds of times more than the number of sand grains on all of Earth’s beaches. There are an estimated 10⁸² atoms in the universe. However, this prodigious number falls far short of accounting for all the matter predicted by the Big Bang. Careful accounting indicates that stars contain only 0.5% of the matter in the universe. Ten times more atoms are presumably floating freely in space. Just 0.03% of the matter is elements other than hydrogen and helium, including carbon and all the building blocks of life.

Looking between galaxies

The intergalactic medium – the space between galaxies – is near-total vacuum, with a density of one atom per cubic meter, or one atom every 35 cubic feet. That’s less than a billionth of a billionth of the density of air on Earth. Even at this very low density, this diffuse medium adds up to a lot of matter, given the enormous, 92-billion-light-year diameter of the universe. The intergalactic medium is very hot, with a temperature of millions of degrees. That makes it difficult to observe except with X-ray telescopes, since very hot gas radiates out through the universe at very short X-ray wavelengths. X-ray telescopes have limited sensitivity because they are smaller than most optical telescopes.

Deploying a new tool

Astronomers recently used a new tool to solve this missing matter problem. Fast radio bursts are intense blasts of radio waves that can put out as much energy in a millisecond as the Sun puts out in three days. First discovered in 2007, scientists found that the bursts are caused by compact stellar remnants in distant galaxies. Their energy peters out as the bursts travel through space, and by the time that energy reaches the Earth, it is a thousand times weaker than a mobile phone signal would be if emitted on the Moon, then detected on Earth. Research from early 2025 suggests the source of the bursts is the highly magnetic region around an ultra-compact neutron star. Neutron stars are incredibly dense remnants of massive stars that have collapsed under their own gravity after a supernova explosion. The particular type of neutron star that emits radio bursts is called a magnetar, with a magnetic field a thousand trillion times stronger than the Earth’s.

Even though astronomers don’t fully understand fast radio bursts, they can use them to probe the spaces between galaxies. As the bursts travel through space, interactions with electrons in the hot intergalactic gas preferentially slow down longer wavelengths. The radio signal is spread out, analogous to the way a prism turns sunlight into a rainbow. Astronomers use the amount of spreading to calculate how much gas the burst has passed through on its way to Earth.

Puzzle solved

In the new study, published in June 2025, a team of astronomers from Caltech and the Harvard Center for Astrophysics studied 69 fast radio bursts using an array of 110 radio telescopes in California. The team found that 76% of the universe’s normal matter lies in the space between galaxies, with another 15% in galaxy halos – the area surrounding the visible stars in a galaxy – and the remaining 9% in stars and cold gas within galaxies. The complete accounting of normal matter in the universe provides a strong affirmation of the Big Bang theory. The theory predicts the abundance of normal matter formed in the first few minutes of the universe, so by recovering the predicted 5%, the theory passes a critical test. Several thousand fast radio bursts have already been observed, and an upcoming array of radio telescopes will likely increase the discovery rate to 10,000 per year. Such a large sample will let fast radio bursts become powerful tools for cosmology. Cosmology is the study of the size, shape and evolution of the universe. Radio bursts could go beyond counting atoms to mapping the three-dimensional structure of the cosmic web.

Pie chart of the universe

Scientists may now have the complete picture of where normal matter is distributed, but most of the universe is still made up of stuff they don’t fully understand. The most abundant ingredients in the universe are dark matter and dark energy, both of which are poorly understood. Dark energy is causing the accelerating expansion of the universe, and dark matter is the invisible glue that holds galaxies and the universe together.

Dark matter is probably a previously unstudied type of fundamental particle that is not part of the standard model of particle physics. Physicists haven’t been able to detect this novel particle yet, but we know it exists because, according to general relativity, mass bends light, and far more gravitational lensing is seen than can be explained by visible matter. With gravitational lensing, a cluster of galaxies bends and magnifies light in a way that’s analogous to an optical lens. Dark matter outweighs conventional matter by more than a factor of five. One mystery may be solved, but a larger mystery remains. While dark matter is still enigmatic, we now know a lot about the normal atoms making up us as humans, and the world around us.

Most normal matter in the universe isn’t found in planets, stars or galaxies – an astronomer explains where it’s distributed

Chris Impey, University Distinguished Professor of Astronomy, University of Arizona This article is republished from The Conversation under a Creative Commons license. Read the original article.