Women who live near natural gas wells in rural Colorado are more likely to have babies with neural tube and congenital heart defects, according to a new study.
As natural gas extraction soars in the United States, the findings add to a growing concern by many activists and residents about the potential for health effects from the air pollutants.
Researchers from the Colorado School of Public Health analyzed birth defects among nearly 125,000 births in Colorado towns with fewer than 50,000 people between 1996 and 2009, examining how close the mothers lived to natural gas wells.
Babies born to mothers living in areas with the highest density of wells – more than 125 wells per mile – were more than twice as likely to have neural tube defects than those living with no wells within a 10-mile radius, according to the study published Tuesday. Children in those areas also had a 38 percent greater risk of congenital heart defects than those with no wells.
Both types of birth defects were fairly rare, occurring in a small percentage of births, but they can cause serious health effects. The researchers did not find a significant association between gas wells and other effects, including oral cleft defects, preterm births and low birth weight.
Neural tube defects, such as spina bifida, are permanent deformities of the spinal cord or brain. They usually occur during the first month of pregnancy, before a woman knows she is pregnant. Congenital heart defects are problems in how the heart's valves, walls, veins or arteries developed in the womb; they can disrupt normal blood flow through the heart.
“Taken together, our results and current trends in natural gas development underscore the importance of conducting more comprehensive and rigorous research on the potential health effects of natural gas development.” –study authors For babies born to mothers in the areas with the most wells, the rate of congenital heart defects was 18 per 1,000, compared with 13 per 1,000 for those living with no wells within a 10-mile radius. For neural tube defects, the rate was 2.87 per 3,000, compared with 1.2 per 3,000 in areas with no wells.
The Colorado Oil and Gas Conservation Commission estimates that 26 percent of the more than 47,000 oil and gas wells in Colorado are located within 150 to 1,000 feet of homes.
“Taken together, our results and current trends in natural gas development underscore the importance of conducting more comprehensive and rigorous research on the potential health effects of natural gas development,” the researchers wrote in the journal Environmental Health Perspectives.
The study was limited in that the researchers didn’t have access to the mothers’ health or socioeconomic information, or their actual exposures to air pollutants. They had to assume that the address when they delivered the baby was the same as during their first trimester. They also knew only if a gas well existed in the year of the births, not how active it was.
Larry Wolk, executive director of the Colorado Department of Public Health and Environment, said no conclusions could be drawn from the study because the researchers didn't know the status of the wells and didn't know the mothers' residential history and health care status.
“Overall, we feel this study highlights interesting areas for further research and investigation, but is not conclusive in itself,” Wolk said in a prepared statement.
“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. Many factors known to contribute to birth defects were ignored in this study," said Wolk, who was appointed to his position by Gov. John Hickenlooper last August.
The Colorado Oil and Gas Association forwarded a request for comment to Dollis Wright, head of an environmental communication company in Colorado.
“They didn’t address things like prenatal care, socioeconomic status and access to health care, which can make all the difference in the world when you look at birth defects,” Wright said.
However, the researchers did take into account the mothers' education, smoking, age, ethnicity, smoking and alcohol use.
Colorado is ranked sixth in the United States for natural gas production, and from 2007 to 20011, the state's production rose 27 percent, according to the U.S. Energy Information Administration.
Two years ago, the lead researcher of the new study, Lisa McKenzie, testified before federal officials recommending stronger state regulation of hydraulic fracturing. She cited a 2012 study she conducted that found carcinogens such as benzene near drilling sites in Garfield County, Colo. McKenzie and colleagues did not know how many of the wells in the new study used hydraulic fracturing.
The study comes on the heels of research from the University of Missouri that found elevated levels of endocrine-disrupting compounds near natural gas drilling in Garfield County. Some chemicals that alter hormones have been linked to birth defects.
It is unclear what, if anything, related to the natural gas wells could raise the risk of birth defects. However, benzene and other hydrocarbons, particulate matter, sulfur dioxide and nitrogen dioxide, are emitted by trucks, drilling and pipelines near the wells.
Benzene previously has been linked to neural tube defects in other areas, including Texas, where exposure is high from petrochemical industries. Benzene and several other air pollutants around natural gas wells are known to cross the placenta from mother to the fetus.
“One plausible mechanism could be an association between air pollutants emitted during development and congenital heart defects, and possibly neural tube defects,” McKenzie said.
McKenzie said she is more cautious about the neural tube findings than the heart findings because the rate was elevated only among women who lived with the highest density of wells, and because there were only 59 babies with the neural defects.
Wright said the study had some “good news for the energy industry” because when the researchers tightened the radius to two and five miles within the mothers’ homes, the odds of some birth defects dropped lower than the odds at 10 miles.
However, for the congenital heart and neural tube defects, increased risk was found at distances of two, five and 10 miles for the mothers living in areas with the highest densities of wells compared with areas with no wells.
Colorado remains torn over natural gas production. Four towns – Broomfield, Fort Collins, Lafayette and Boulder – last year passed initiatives to ban or place a moratorium on fracking. The Colorado Oil and Gas Association filed a lawsuit trying to stop the bans in Fort Collins and Lafayette.
Communities should decide whether they want to put pregnant mothers at risk, said Lindsey Wilson, a field associate with Environment Colorado, an environmental group.
“The findings in this study clearly show how important it is that Colorado state officials allow communities to make their own decisions on whether or not to allow fracking within their borders,” Wilson said.