Pittsburgh: Pregnant women living close to a high density of natural gas wells drilled with hydraulic fracturing were more likely to have babies with lower birth weights than women living farther from such wells, according to a University of Pittsburgh Graduate School of Public Health analysis of southwestern Pennsylvania birth records. The finding does not prove that the proximity to the wells caused the lower birth weights, but it is a concerning association that warrants further investigation, the researchers concluded. The study was funded by The Heinz Endowments and published in the current issue of PLOS ONE.
“Our work is a first for our region and supports previous research linking unconventional gas development and adverse health outcomes,” said co-author Bruce Pitt, Ph.D., chair of Pitt Public Health’s Department of Environmental and Occupational Health. “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 includes horizontal drilling and
high volume hydraulic fracturing, known as “fracking.” It allows access
to large amounts of natural gas trapped in shale deposits. Prior to
2007, only 44 wells were known to be drilled in Pennsylvania’s Marcellus
Shale with such technology. From 2007 to 2010, that expanded to 2,864
wells.
The Pitt Public Health research team cross-referenced birth
outcomes for 15,451 babies born in Washington, Westmoreland and Butler
counties from 2007 through 2010 with the proximity of the mother’s home
to wells drilled using unconventional gas development. They divided the
data into four groups, depending on the number and proximity of wells
within a 10-mile radius of the mothers’ homes.
Mothers whose homes fell in the top group for proximity to a high
density of such wells were 34 percent more likely to have babies who
were “small for gestational age” than mothers whose homes fell in the
bottom 25 percent. Small for gestational age refers to babies whose
birth weight ranks them below the smallest 10 percent when compared to
their peers.
The researchers took into account many factors that could influence
a newborn’s weight – including whether the mother smoked, her prenatal
care, race, education, age and whether she’d had previous babies, as
well as the gender of the baby – and the finding still held.
“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.”
In southwestern Pennsylvania, the waste fluids produced through
hydrofracturing, called “flowback,” can contain benzene. Unconventional
gas development also creates an opportunity for air pollution through
flaring of methane gas at the well heads and controlled burning of
natural gas that releases volatile organic compounds, including benzene,
toluene, ethylbenzene and xylene. Increased truck traffic and
diesel-operated compressors also can contribute to air and noise
pollution.
“It is important to stress that our study does not say that these
pollutants caused the lower birth weights,” said Dr. Pitt.
“Unconventional gas development is dynamic and varies from site to site,
changing the potential for human exposure. 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.”