Updated on December 13 at 6:30 p.m.
Hydraulic fracturing, or fracking, may pose a significant—but very local—harm to human health, a new study finds. Mothers who live very close to a fracking well are more likely to give birth to a less healthy child with a low birth weight—and low birth weight can lead to poorer health throughout a person’s life.
The research, published Wednesday in Science Advances, is the largest study ever conducted on fracking’s health effects.
“I think this is the most convincing evidence that fracking has a causal effect on local residents,” said Janet Currie, an economist at Princeton University and one of the authors of the study.
The researchers took the birth records for every child born in Pennsylvania from 2004 to 2013—more than 1.1 million infants in total—and looked at the mother’s proximity to a fracking site, using the state of Pennsylvania’s public inventory of fracking-well locations. They used private state records that showed the mother’s address, allowing them to pinpoint where every infant spent its nine months in utero.
They found significant, but very local, consequences. Infants born to mothers who lived within two miles of a fracking well are less healthy and more underweight than babies born to mothers who lived even a little further away. Babies born to mothers who lived between three and 15 miles from a fracking well—that is, still close enough to benefit financially from the wells—resembled infants born throughout the rest of the state.