Scientists from Duke University and Boston University have discovered more than 5,800 leaks from aging natural gas pipelines under the streets of Washington, D.C., including some issuing explosive levels of methane, according to an article in USA Today.

Researchers dispatched a car equipped with measuring instruments across the city last January and February. Their findings appear in the most recent issue of Environmental Science & Technology.

Methane was leaking at high concentrations at 19 spots, and the researchers conducted additional tests by putting gas probes into manholes. They found that 12 of those 19 leak sites had methane levels more than high enough to cause an explosion – in some cases 10 times as high, the article states.

“In February, they reported the leaks to Washington Gas, the local utility, but upon follow-up testing four months later, found nine of them were still emitting dangerous levels of methane,” the article states.

 “If you dropped a cigarette down a manhole ... it could have blown up,” Robert Jackson told USA Today. He is a professor of environmental sciences at Duke who led the study. “I was shocked,” he says.

“Pipeline leaks are drawing more attention as natural gas production and use booms in the United States,” the article states. “The Duke and Boston researchers say these leaks are the nation’s largest human-caused source of methane, contributing to the $3 billion of natural gas that’s lost or unaccounted for each year.”

In addition to creating risk of explosions, the leaks release methane, which is the principle ingredient in natural gas and a potent greenhouse gas that contributes to global warming. “Climate-wise, it’s potentially a big deal,” Jackson told USA Today. Methane can trap more than 20 times as much heat in the atmosphere as carbon dioxide.

To read the USA Today article, click here.