A new study that matched the location of Pennsylvania shale gas wells with the home addresses of new mothers indicated that pregnant women living within 1 kilometer of fracking activity have a 25% greater chance of having low-birth-weight babies than mothers that live further away.
The baseline risk of low birth weight in Pennsylvania is 6.5%, according to the study. In the study of Pennsylvania data by three university researchers, mothers within 1 km of a fracked well had an additional 1.6% chance of delivering a low-birth-weight baby.
Babies with low birth weights, defined as less than 5.5 pounds, are at risk for a number of negative health consequences ranging from infant death to asthma to lower school performance, previous research has shown. Infant health data is useful for studying the health effects of fracking because of the sensitivity of fetuses to pollution effects and the ability to pinpoint pollution exposure to a specific location within a nine-month window, the study authors said.
"The results suggest that the introduction of fracking reduces health among infants born to mothers living within 3 km of a well site during pregnancy," the authors concluded. "We find the largest effects for mothers living within 1 km of a site — a 25% increase in the probability of a low–birth-weight birth."
Natural gas industry trade groups pushed back hard against the study.
"This study's methodology fails to account for a wide range of basic yet highly critical public health factors," Marcellus Shale Coalition spokeswoman Erica Clayton Wright said in a Dec. 14 email.
"For example, the researchers failed to consider crucial issues linked to low birth weights like smoking as well as alcohol and drug use," she said. "The authors even acknowledge that actual exposure levels weren't measured and that their so-called conclusions were based off a sample group that's already more likely to experience premature and low-birth-weight deliveries."
"Given these deep methodological flaws, it's dangerously misleading and inflammatory to suggest that natural gas development has done anything but improve public health," Wright said.
"The authors even concede that their findings could have absolutely nothing to do with fracking," Seth Whitehead, who contributes to the Independent Petroleum Association of America-sponsored Energy in Depth, wrote after the study's release.
The study compared home addresses and the weights of 1.1 million babies in Pennsylvania born between 2004 and 2013 with the location of new shale wells and found the risk of low birth weights increased within 3 km of shale wells. The 25% increase in risk within 1 kilometer generally dropped to about one-third or one-half for mothers living in a range of 1 km to 3 km from a shale well, according to the study.
"There is little evidence of health effects at further distances, suggesting that health impacts are highly local," the authors said.
Using national databases from both commercial and government sources, the study estimated as many as 65,000 babies were born between July 2012 and June 2013 nationwide to mothers who lived less than 1 km from a an unconventional well.
The study was published Dec. 13 in the peer-reviewed journal Science Advances. The study authors are Janet Currie, the chairman of Princeton University's Department of Economics and Director of Princeton's Center for Health and Wellbeing; the University of Chicago's Energy Policy Institute Director Michael Greenstone; University of California, Los Angeles assistant economics professor Katherine Meckel.
The authors noted there were limits to the conclusions in the database-driven report. It did not measure pollution, it did not identify a pathway to exposure and the number of births near shale wells is small.
The researchers also said they did not examine "wealth effects" on pregnant women near fracked wells. "If, for example, women living near wells receive income from mineral rights, then the higher income per se could be expected to confer a health benefit, which might partially offset the negative effects of fracking-related pollution," the study said.