Children in Pennsylvania who grew up within roughly a mile of fracking wells are twice as likely as other young people to develop the most common form of juvenile leukemia, according to a new study by researchers at the Yale School of Public Health.

The study, published Wednesday in the journal Environmental Health Perspectives, also found that children born to pregnant women who lived near fracking wells were nearly three times as likely as other newborns to be diagnosed with leukemia.

The research, part of a registry-based study which drew on such information as patient health histories and geographic data, was based on a review of records for about 2,500 children, roughly 400 of whom were being treated for acute lymphoblastic leukemia, the most widely diagnosed form of childhood leukemia also known as ALL.

Fracking, or hydraulic fracturing, is a process through which chemicals, water and other substances are injected into the ground at high pressure to allow for the extraction of oil and natural gas. Fracking is also considered a form of unconventional oil and gas development when compared to more traditional methods of drilling.

Pennsylvania is the site of roughly 13,000 unconventional natural gas wells, according to the state department of Health, and the study’s researchers noted that from 2005 to 2014, more than 1,000 spills, 5,000 violations and 4,000 complaints from residents related to oil and gas had been recorded.

Environmentalists and others have long criticized the practice, which can pollute groundwater and release greenhouse gases into the air. Oil and gas production operations have also been associated with the release of known or suspected carcinogens such as benzene and polycyclic aromatic hydrocarbons.

“What our results really indicate is that exposure to unconventional oil and gas development may be an important risk factor for ALL, particularly for those children that are exposed in utero,” said Cassandra Clark, the lead author of the study.

Clark and her co-researchers examined cases of children between the ages of 2 and 7 who were diagnosed with acute lymphoblastic leukemia from 2009 to 2017. The children with the highest occurrences of the disease lived within 2 kilometers, or about a mile and a quarter, of fracking wells.

Currently, researchers said, Pennsylvania law allows fracking wells to operate within 500 feet (or 152 meters) of a private residence.

Clark said that her team’s findings suggest that the minimum distance between fracking wells and residences should be increased. The study noted an increased risk for acute lymphoblastic leukemia among children who lived as far as 10 kilometers, or about 6 miles, from a fracking well.

The study “highlights the need to revisit our public health policy protections and some of the distances that exist,” said Nicole Deziel, who also worked on the study. 

“The allowable distance for how close to oil and gas wells can be to homes and schools and other sensitive receptors can be as small as 150 feet in some states,” said Deziel, who is an associate professor of epidemiology. “And we think that our study really highlights and augments that growing body of studies indicating that there are increased health problems to children, and that some of these public health policies need to be updated with newer information.”

Besides the geographic proximity of children to fracking wells themselves, the researchers said that they also produced models of potential exposure to drinking water that was contaminated by the chemicals used in fracking processes.

Those models showed that children who lived within roughly a mile of a well located near a source of groundwater were twice as likely to develop acute lymphoblastic leukemia as other children. Children who lived within about 3 miles of wells located near a water source were 1.5 times as likely to be diagnosed with leukemia as other children.

Researchers said that they hope that policymakers will utilize the findings of their work and other studies to identify ways to help children stay safer.

“This is not really something that can be managed on an individual level,” Deziel said. “The burden shouldn’t be on individuals and parents to try to figure this out. This really requires higher level solutions to make sure communities are safe and that their children are adequately protected from oil and gas drilling operations.”

Joan Casey, an assistant professor of environmental health sciences at Columbia University’s Mailman School of Public Health who was not a part of this study, said she was not surprised by the findings. 

“There’s a relatively robust literature now that shows elevated levels of non-methane, volatile organic compounds in the air close to wells and some of those, like benzene, are known carcinogens,” said Casey, who has studied maternal health and birth outcomes in connection to fracking. “So there’s certainly a plausible pathway through the air linking proximity to wells with increased risk of cancer.”

Casey also said the fracturing fluid that is injected into the well in order to release the oil and gas, “contains a number of carcinogens.” 

“And so if there are any well failures and some of that fluid is able to escape and contaminate water sources that people either drink or recreate in, that could be another pathway through which risk of cancer could be increased,” she said.

Casey, who said she believes more studies will follow this one, added that the fracking process results in the expulsion of methane, “which is a really potent greenhouse gas, 80 times more potent than CO² over a 20 year period.”

“Climate change is the biggest health threat of fracking,” she said. “While there are many other potential short-term implications of hydraulic fracturing for health, its contribution to climate change for me is my biggest concern.”