A University of Colorado study concluding that certain birth defects are as much as 30 percent more common among mothers living near natural gas wells has come under question by the state public health department.
The tussle comes as an entrenched political conflict over the future of oil and gas drilling in the state has made a Rorschach test out of epidemiology, with each side seeing what they want to see when it comes to health risks.
The research, led by scholars at the Colorado School of Public Health and published last week in the journal Environmental Health Perspectives, found that mothers living within 10 miles of natural gas wells in rural Colorado were more likely to give birth to babies with congenital heart defects. The research didn’t prove that drilling caused the defects.
The study made use of state health department records of 124,842 births from 1996 to 2009. But in an unusual show of dissension, the health department threw water on the findings. Chief Medical Officer Larry Wolk, appointed in August by Gov. John Hickenlooper, cautioned in a lengthy statement that “people should not rush to judgment.”
"Many factors known to contribute to birth defects were ignored in this study."
The state official criticized the study’s design and highlighted its limitations. Inactive wells weren’t distinguished from active wells, Wolk noted, while findings on neural tube defects didn’t account for factors like prenatal health care, drinking or smoking. On top of that, the study only made use of the mothers’ addresses at the time of their babies’ birth, and didn’t account for women who might have moved after the first trimester, when most birth defects occur.
“As Chief Medical Officer, I would tell pregnant women and mothers who live, or who at-the-time-of-their-pregnancy lived, in proximity to a gas well not to rely on this study as an explanation of why one of their children might have had a birth defect,” said Wolk. “Many factors known to contribute to birth defects were ignored in this study.”
The state health department’s volley is set amid a pitched battle over energy development in Colorado. Environmentalists have faced off against industry groups, and local moratoriums on the drilling process known as hydraulic fracturing, or fracking, have butted against the relatively industry-friendly approach of Hickenlooper.
Questions about fracking’s health impacts rest uneasily at the center of the political storm. Fracking sends a slurry of water, sand and chemicals deep underground to break up horizontal layers of oil and gas. The process has re-animated oil and gas drilling in the U.S., leading to a domestic energy boom. It has also enlivened the environmental movement in the country, as opponents of the practice raise concerns about air and water pollution from the often-mysterious brew of chemicals used by energy companies.
The way each side frames the health risks of the practice can be revealing, says Chuck Davis, a political scientist at Colorado State University.
“Oil and gas folks frame it in terms of scientific uncertainty,” calling up the other possible forms of pollution or health conditions that might confound any attempt to identify a culprit in disease, says Davis. “The environmentalists and others will say, these are people who are immediately impacted; they’d argue for the precautionary principle.”
This principle calls for taking precautions to address plausible harm to human health or the environment, even when the science is uncertain.
Davis draws a parallel to the early debate on cigarettes’ link to lung cancer. Tobacco companies highlighted the uncertainty of linking a complex disease to a single cause, while activists played up the risks and advocated safeguards.
Here, as in the tobacco debate, the stakes are high.
There are now 51,717 oil and gas wells across the state, according to a recent count by the Colorado Oil and Gas Conservation Commission.
For a growing number of Coloradans, drilling’s effect on air and water is a matter of local concern. Fort Collins, Boulder and Lafayette recently enacted bans or moratoriums on fracking. Longmont did the same in 2012.
The oil and gas industry has fought the efforts by carrot and stick, suing the cities that have voted to ban or suspend fracking while launching an extensive public marketing campaign to burnish its image in the state. Major energy companies Anadarko Petroleum Corporation and Noble Energy created a nonprofit, Coloradans for Responsible Energy Development, which has spent heavily on ads touting the safety of the drilling method.
Hickenlooper has sided mainly with the industry, appearing in pro-fracking ads sponsored by the energy industry and joining a lawsuit to overturn Longmont’s ban. At the same time, the state has proposed rules that would restrict methane emissions and other air pollution from oil and gas drilling.
Interpreting scientific findings like CU’s latest in such a din can be difficult.
So what did the study actually say? The findings described a higher rate of congenital heart defects in areas where wells are densely concentrated. Mothers living near an area of more than 125 wells per mile were roughly 30 percent more likely to have a baby with a congenital heart defect than those giving birth near no wells at all.
The researchers raised the possibility of exposure to benzene — a known byproduct of drilling — and other air pollutants previously linked to birth defects as a potential cause.
Neural tube defects were twice as common in areas of densely concentrated wells, but lead author Lisa McKenzie cautioned against reading too much into this. Neural tube defects are very rare, and only 59 were recorded in all the years studied.
The researchers also looked at oral clefts, and premature or low birthweight infants. But they didn’t find much there, except an inexplicable — and very small — association in the other direction; women living near wells were actually slightly less likely to have premature or low-weight babies.
"Communities should decide for themselves whether they want to put pregnant mothers in danger."
The study was punctuated with a long list of acknowledged limitations in the available data — including many of the same caveats highlighted by the health department.
Jane McElroy, a University of Missouri epidemiologist and author of an unrelated study that found a link between birth defects and fracking fluids, applauded CU’s research as a valuable foray into a field that’s been largely unexplored.
Lindsey Wilson, an anti-fracking activist from Environment Colorado, read the findings as support for a policy of local autonomy when it comes to energy development.
“Communities should decide for themselves whether they want to put pregnant mothers in danger,” said Wilson.
The oil and gas folks were mostly silent, preferring to let the health department make their case. Doug Flanders, a spokesman for the Colorado Oil and Gas Association, referred a reporter to Wolk’s statement.
The tone of the health department’s response surprised David Savitz, a Brown University epidemiologist and a co-author of the study, striking him as “defensive” and “an overreaction.”
“I share many of the concerns,” said Savitz. “It’s certainly not a conclusive study, and it doesn’t demonstrate that pollutants related to shale development have caused birth defects.”
But Savitz stood behind the findings of the study as a clear step forward from anecdotal information that’s been available previously.
“What I would expect from the public health agency would be to acknowledge that there are legitimate questions and that this has advanced our ability to frame it more clearly … and to pursue better research either to show where this one went awry or to provide additional evidence on the same question,” Savitz said.
In other words, to answer science with more science.
The scientific process itself, added lead author McKenzie, is intended to guard against the kind of grandstanding that has characterized the debate over fracking.
“This manuscript has gone through really extensive peer review,” said McKenzie. “Comments on the web and press releases don’t get the same review.”
I-News is the public service journalism arm of Rocky Mountain PBS. Contract Kristin Jones at kristinjones@rmpbs.org.
