A new study has found an association between hydraulic fracturing, or fracking, and smaller babies.
The scientists used data on 15,451 live births in southwest Pennsylvania from 2007 to 2010.
They categorized the mothers by how close they lived to gas wells and the concentration of wells in the area.
Babies born in the highest exposure areas were not at higher risk of being born prematurely, but they were 34 percent more likely to be small for gestational age than those born in areas of least exposure.
The analysis, published in PLOS One, was observational and did not prove causality. The researchers controlled for mother’s age, race, prenatal care, smoking during pregnancy and other health and behavioral factors.
The reasons for the association are unclear, but the authors suggest that liquids used in the drilling may present a risk of air and water pollution.
“This isn’t enough to cause changes in policy,” said a co-author, Bruce R. Pitt, the chairman of the department of environmental and occupational health at the University of Pittsburgh Graduate School of Public Health.
“It requires more intensive research, better measurements of exposure and medical outcomes. But it is enough to prompt further research so that we know how to go forward in a way compatible with public and environmental health.”
A spokesman for the Marcellus Shale Coalition, a trade industry group, said, “The researchers by their own admission rely heavily on two anti-oil and natural gas studies that have been thoroughly debunked. They admit that ‘a number of unknown factors limit the research.’ “