For years, the controversy over natural gas drilling has focused on the water and air quality problems linked to hydraulic fracturing, the process where chemicals are blasted deep underground to release tightly bound natural gas deposits.
But a new study reports that a set of chemicals called non-methane hydrocarbons, or NMHCs, is found in the air near drilling sites even when fracking isn't in progress.
According to a peer-reviewed study in the journal Human and Ecological Risk Assessment, more than 50 NMHCs were found near gas wells in rural Colorado, including 35 that affect the brain and nervous system. Some were detected at levels high enough to potentially harm children who are exposed to them before birth.
The authors say the source of the chemicals is likely a mix of the raw gas that is vented from the wells and emissions from industrial equipment used during the gas production process.
The paper cites two other recent studies on NMHCs near gas drilling sites in Colorado. But the new study was conducted over a longer period of time and tested for more chemicals than those studies did.
"To our knowledge, no study of this kind has been published to date," the authors wrote.
The researchers took weekly air samples at a site that's within one mile of 130 gas wells in Garfield County, Colo., with little other industry aside from natural gas production. They detected more than 50 chemicals between July 2010 and October 2011, including 44 with reported health effects. The highest concentrations were measured after new wells were drilled, but the concentrations did not increase after the wells were fracked.
Carol Kwiatkowski, one of the study's authors, said that because of limitations on funding and access to drilling sites, the study doesn't definitively link the gas fields to the air pollutants. But because the research was conducted in a region with few people and roads, "natural gas drilling would be the first thing anyone would look at."
What the study shows, she said, is that more research is needed on all stages of gas production. "It's not all about fracking. ... Air pollution needs more focus and scrutiny."
Kwiatkowski is executive director of the Endocrine Disruption Exchange (TEDX), a nonprofit research organization in Colorado that studies the impact of environmental pollutants on the endocrine system, a network of hormone-producing glands that affects nearly every organ in the body. TEDX has spent years studying the health effects of natural gas drilling, and its reports are routinely criticized by the industry.
Kathleen Sgamma, vice president of government and public affairs at Western Energy Alliance, which represents oil and gas drillers in the American West, said the TEDX scientists have produced "a study that clearly doesn't come up with the results they're trying to show." Sgamma questioned the scientists' qualifications, as well as the quality of the journal that published their findings. "This was clearly not a well-thought out and well peer-reviewed study," she said.
But Robert Jackson, a professor of energy and environmental studies at Duke University who was not involved in the research, said the study is valuable because it shows that more study is needed about how drilling affects communities near gas fields.
"There's the question of whether there are long-term health effects," he said. "It warrants a follow-up [health] study."
Many residents of the sparsely populated area live within a mile of active wells. 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.
All of the chemicals TEDX detected were at levels well below the limits the federal government recommends to protect workers from dangerous chemicals. However, those standards are usually designed for healthy adult males who are exposed to the chemicals on and off for 40 hours a week. Scientists say the risks would likely be different for people—including pregnant women, children and the elderly—who live near gas fields and are exposed 24 hours a day, seven days a week.
"We've been overlooking these non-methane hydrocarbons until now," said Theo Colborn, president of TEDX and the paper's lead author. "They've been measured before in cities ... otherwise, no one has looked at [them] as related to natural gas drilling in rural areas."
What the Scientists Found
Non-methane hydrocarbons are emitted by industrial equipment and also by unprocessed natural gas.
When an operator drills a new well, most of the raw gas that flows out of the ground is methane—the target compound that's collected and sold. The gas also contains water and dozens of NMHCs, including the carcinogen benzene. On average, NMHCs account for 18 percent of the unprocessed gas and are released into the air at various stages of production.
John Starck, an engineer and president of EGL Resources, a Texas oil and gas company, said very little raw gas escapes during the initial drilling phase, because the gas-bearing rock is so impermeable. Once the well has been fracked, the quantities of NMHCs released would be on the order of parts per thousand or parts per million, unless there is a leak, he said.