Pregnant women living close to unconventional gas drilling sites may be at a heightened risk of delivering babies with low birth weights, according to a new analysis of Pennsylvania birth records.
The study, published in PLOS ONE, found a significant association between proximity to fracking sites during pregnancy and decreased infant birth weight. While the study can’t establish causality, the researchers say the correlation is strong enough to warrant concern, and should be investigated more closely in larger studies.
“Our work is a first for our region and supports previous research linking unconventional gas development and adverse health outcomes,” said co-author Dr. Bruce Pitt. “These findings cannot be ignored. There is a clear need for studies in larger populations with better estimates of exposure and more in-depth medical records.”
Unconventional gas development can include horizontal drilling as well as hydraulic fracturing, commonly called “fracking,” which allows companies to access large pockets of natural gas tightly bound in shale deposits. Before 2007, such technologies were used in just 44 wells drilled in the Marcellus Shale region of Pennsylvania; between 2007 and 2010, that number grew to more than 2,800 wells, the researchers report.
As gas drilling expands throughout the nation, production is moving closer to populated areas, with wells in some states now being drilled within a few hundred feet of schools and homes. This has prompted a host of new health and environmental concerns, particularly among those living close to drilling sites.
According to a 2014 review of health-related studies on fracking, the current scientific research puts forward “both substantial concerns and major uncertainties to address,” including contamination of groundwater and drinking water supplies, and the release of a variety of toxic pollutants into the air.
For this latest study, Dr. Pitt’s team gathered data on natural gas wells and births for the Butler, Washington and Westmoreland counties of Pennsylvania for 2007-2010, including a total of 15,451 births. They then divided the birth data into four groups, based on the number and proximity of gas wells within a 10-mile radius of the mothers’ homes.
The results showed that the group of mothers who lived closest to a high density of fracking wells were 34% more likely to give birth to infants who were small for gestational age — those with birth weights below the smallest 10% when compared with their peers — than the group of mothers who lived farthest away.
Notably, this finding still held after adjusting for other factors that could influence birth weight, including prenatal care, race and whether the mother smoked or not.
“Developing fetuses are particularly sensitive to the effects of environmental pollutants,” said Dr. Pitt. “We know that fine particulate air pollution, exposure to heavy metals and benzene, and maternal stress all are associated with lower birth weight.”
This study is not the first to suggest a link between proximity to drilling sites and adverse birth outcomes. In a 2014 analysis of almost 125,000 birth records in rural Colorado, researchers found that pregnant women who lived the closest to fracking wells were 30% more likely to have infants with congenital heart defects than women who lived the farthest away.
Many aspects of the fracking process are thought to contribute to pollution in the surrounding area. Waste fluids known as “flowback” can contain benzene and other harmful chemicals, while high levels of iodide can promote the formation of highly toxic byproducts in drinking water processed at municipal treatment plants downstream from oil and gas operations. Additionally, the flaring of methane gas at well heads can release volatile compounds such as toluene, ethylbenzene and xylene into the air. In one recent study of drilling sites in Arkansas, Colorado, Ohio, Pennsylvania, New York and Wyoming, researchers found concentrations of volatile compounds exceeding safe levels in 38% of the 76 air samples they analyzed.
Dr. Pitt says it is important to stress that their study does not confirm that these pollutants caused the lower birth weights, noting that exposure is difficult to measure and may be influenced by a number of factors.
“Unconventional gas development is dynamic and varies from site to site, changing the potential for human exposure,” he said. “To draw firm conclusions, we need studies that thoroughly assess the exposure of a very large number of pregnant women to not just the gas wells, but other potential pollutants.”
According to research from Cornell University, at least 75 percent of the more than 600 chemicals used in fracking are known to cause respiratory, gastrointestinal, dermatological, and ocular effects; 40 percent to 50 percent are known to be neuro-, immuno- and/or nephrotoxic; 40 percent are endocrine disruptors; and 25 percent are carcinogenic.