horses in field

Fracking linked to rare birth defect in horses: Study

The implications for human health are "worrisome," say researchers.

A new study has uncovered a link between fracking chemicals in farm water and a rare birth defect in horses—which researchers say could serve as a warning about fracking and human infant health.


The study, published this month in the journal Science of the Total Environment, complements a growing body of research linking fracking to numerous human health effects, including preterm births and high-risk pregnancies. This is believed to be the first study to find fracking chemicals in farm water linked to birth defects in farm animals.

In 2014, veterinarians at the Cornell University Hospital for Animals in Ithaca, New York, realized that they'd diagnosed five out of 10 foals born on one farm in Pennsylvania with the same rare birth defect. The birth defect, dysphagia, involves difficulty swallowing caused by abnormalities in the throat. Dysphagia causes nursing foals to inhale milk instead of swallowing it, which often results in pneumonia if milk gets into their lungs.

"We'd hear a gurgling sound when the foals nursed, and we confirmed they were dysphagic by using video endoscopy to look for milk in their tracheas, instead of in their esophagus where it should be," Kathleen Mullen, a veterinarian and the study's lead author, told EHN. "We treated them by passing a feeding tube so they could eat, and if there was pneumonia from the aspiration, we treated that with antibiotics. The foals generally recovered with time, but some never nursed again."

The birth defect is so rare that the rate among the general population isn't known, but one paper on health outcomes in horses from a large university veterinary neonatal intensive care unit documented just five cases of dysphagia out of 1065 hospitalized foals—a rate of less than 0.5 percent.

The owner of the Pennsylvania farm the horses came from also owned a farm in New York. Both farms used the same commercial horse feed and sourced hay from the same place—but none of the horses born on the New York farm ever had dysphagia. Additionally, several mares that lived on the Pennsylvania farm for the first half of their gestation had healthy foals after being moved to the New York farm mid-pregnancy, while several mares who started out in New York and were moved to Pennsylvania mid-pregnancy had dysphagic foals.

The only difference the farmer identified was that in Pennsylvania, there were 28 fracking wells within seven miles of the farm—two of which were within 1,500 feet of the property's two water wells. There were no fracking wells near the New York farm. The state banned the practice in 2015 following a seven-year review of its health and environmental impacts, during which time there was a moratorium on it.

"We realized this was a really rich study opportunity," Mullen said, "so we decided to look more closely to see if environmental factors were associated with the dysphagia cluster."

Over the next two years, Mullen and colleagues analyzed samples of feed, soil, air, and water, and samples of blood and tissue samples from mares and foals at both farms. During that time, 65 foals were born, 17 of which were dysphagic—all of them from the Pennsylvania farm.

horses farm

Credit: Paz Arando/Unsplash

They didn't find significant differences in the feed, soil, air, or blood and tissue samples from the two farms. But they did find a significant difference in the water: There were higher levels of four kinds of polycyclic aromatic hydrocarbons (PAHs)—chemicals commonly used in fracking—in the water at the Pennsylvania farm that weren't seen in water at the New York farm. Those chemicals included fluoranthene, pyrene, 3,6-dimethylphenanthrene, and triphenylene, all of which have been linked to health problems in humans and animals.

Following that discovery, the farmer installed a water filtration system, which brought the levels of PAHs in the water on the Pennsylvania farm down to levels comparable to those seen at the New York farm. After that, they saw a marked decrease in the birth of dysphagic foals: In 2014, 26 percent of all of the farmer's foals had been born dysphagic; in 2015, 41 percent were dysphagic; and in 2016, after the installation of the filtration system, the rate fell to 13 percent.

The researchers believe the reduction in PAHs in the water, along with a reduction in the amount of time the mares were spending on the Pennsylvania farm during their pregnancy, led to the corresponding reduction in birth defects in the horses—though Mullen added that more research is needed to evaluate the toxicity of those chemicals at the levels they observed.

"I think it's a bit soon to say that all farms should have filtration systems installed for their wells," she said, "but this study does provide at least preliminary evidence that well water in places with unconventional natural gas development can see increased levels of PAHs."

A spokesperson for the Pennsylvania Farm Bureau told EHN the organization hasn't yet had time to fully review the study, but noted that "animal health is among the top priorities for Pennsylvania farmers, and scientific research plays a critical role in helping farmers develop practices to best care for their animals and understand factors that may affect their animals' health."

Mullen said she believes the study adds to the growing body of literature linking fracking to problems with human fetal development.

"Horses are often sentinels of health risks to humans," she said. "Right now we can only speculate that what we saw in these foals also translates to human health risk, but the implications are certainly worrisome."

Banner photo credit: Soledad Lorieto/Unsplash

A piece of wood with green leaves in the shape of the world's continents on it.

Trump administration’s shutdown of USAID devastates global conservation efforts

After a sweeping dismantling of the U.S. Agency for International Development, conservation projects protecting wildlife, forests, and ecosystems across dozens of countries are collapsing due to funding cuts.

Adam Welz reports for Yale Environment 360.

Keep reading...Show less
Sunrise in the woods

Get our Good News newsletter

Get the best positive, solutions-oriented stories we've seen on the intersection of our health and environment, FREE every Tuesday in your inbox. Subscribe here today. Keep the change tomorrow.

Two nuclear towers in the distance with smoke emitting from them

Trump’s nuclear revival plan faces obstacles at Tennessee Valley Authority

The Trump administration's push for a nuclear energy renaissance faces internal turbulence at the Tennessee Valley Authority (TVA), with leadership shake-ups and tariff policies threatening to slow progress rather than speed it up.

Gautama Mehta and Katie Myers report for Grist.

Keep reading...Show less
A woman looks at a handmade journal that includes pressed flowers and leaves.

Independent bookshops are helping people fight climate despair with the right stories

In the UK, three indie bookstores are blending climate action and storytelling to help readers find hope, connection, and purpose in the face of planetary crisis.

Lottie Limb reports for Euronews.

Keep reading...Show less
A river runs between hills covered with trees displaying fall foliage colors.
Credit: Photo by Liz Guertin/Unsplash

Maryland’s conservation streak shows how far a small state can go

Maryland just became the first U.S. state to meet the “30 by 30” conservation goal — six years early — and it's already aiming for 40% by 2040.

Cara Buckley reports for The New York Times.

Keep reading...Show less
A woman stands in front of a garbage dump next to an abandoned building holding a poster that says "there is no planet b."

Environmental groups brace for a new era of fear and federal targeting

As the Trump administration sharpens its attacks on environmental nonprofits, Earthjustice president Abigail Dillen warns the movement is under threat like never before.

Sharon Lerner reports for ProPublica.

Keep reading...Show less
A copy of Pope Francis' Laudato Si encyclical propped against a wooden pew in a church with the pope's photo on the cover.
Credit: Johan Bergström-Allen / www.carmelite.org/FlickrCreative Commons Attribution 2.0 no restrictions

Pope Francis made climate change a moral crisis. Following his death, the world needs a new voice

Pope Francis turned the climate crisis into a global moral reckoning, but as the planet warms, his loss leaves a gaping hole in the fight for climate justice.

Chico Harlan reports for The Washington Post.

Keep reading...Show less
blue and white solar panels on green grass.

Clean energy tech is outpacing politics and reshaping the global power landscape

Even as the Trump administration moves to expand fossil fuels and slash climate regulations, clean energy industries are accelerating beyond the reach of political backlash.

The Vox climate team sets out to analyze the clean energy transition in a special, multi-story project.

Keep reading...Show less
From our Newsroom
Regulators are underestimating health impacts from air pollution: Study

Regulators are underestimating health impacts from air pollution: Study

"The reality is, we are not exposed to one chemical at a time.”

Pennsylvania governor Josh Shapiro speaks with the state flag and American flag behind him.

Two years into his term, has Gov. Shapiro kept his promises to regulate Pennsylvania’s fracking industry?

A new report assesses the administration’s progress and makes new recommendations

silhouette of people holding hands by a lake at sunset

An open letter from EPA staff to the American public

“We cannot stand by and allow this to happen. We need to hold this administration accountable.”

wildfire retardants being sprayed by plane

New evidence links heavy metal pollution with wildfire retardants

“The chemical black box” that blankets wildfire-impacted areas is increasingly under scrutiny.

People  sitting in an outdoors table working on a big sign.

Op-ed: Why funding for the environmental justice movement must be anti-racist

We must prioritize minority-serving institutions, BIPOC-led organizations and researchers to lead environmental justice efforts.

joe biden

Biden finalizes long-awaited hydrogen tax credits ahead of Trump presidency

Responses to the new rules have been mixed, and environmental advocates worry that Trump could undermine them.

Stay informed: sign up for The Daily Climate newsletter
Top news on climate impacts, solutions, politics, drivers. Delivered to your inbox week days.