Gas field blamed in pollutant’s spike

WASHINGTON — An oil and natural-gas field in the western United States is largely responsible for a global uptick of the air pollutant ethane, according to a new study.

The team led by researchers at the University of Michigan found that fossil-fuel production at the Bakken Formation in North Dakota and Montana is emitting roughly 2 percent of the ethane detected in the Earth’s atmosphere.

Along with its chemical cousin methane, ethane is a hydrocarbon that is a significant component of natural gas. Once in the atmosphere, ethane reacts with sunlight to form ozone, which can trigger asthma attacks and other respiratory problems, especially in children and the elderly. Ethane pollution also can harm agricultural crops. Ozone also ranks as the third-largest contributor to human-caused global warming after carbon dioxide and methane.

“We didn’t expect one region to have such a global influence,” said Eric Kort, lead author of the study and an assistant professor of climatic science at the University of Michigan in Ann Arbor.

The study was begun after a mountaintop sensor in the European Alps began registering surprising spikes in ethane concentrations in the atmosphere starting in 2010, after decades of declines. The increase, which has continued over the past five years, was noted at the same time new horizontal drilling and hydraulic fracturing techniques were fueling a boom of oil and gas production from previously inaccessible shale rock formations in the United States.

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