New research demonstrates that it's hard to nail down how often natural gas drilling is contaminating drinking water.
A Duke University study released Monday found high levels of methane pollution in some Pennsylvania water wells within a half-mile from drilling, while another from the U.S. Geological Survey found some serious methane pollution occurring naturally, far from drilling.
Duke researcher Rob Jackson said their paper shows that methane contamination is "not an epidemic" but does exist. Methane is an odorless gas that is not known to be toxic, but high concentrations can be explosive.
The Marcellus Shale Coalition, an industry group, had no direct comment on the Duke findings. CEO Kathryn Klaber said private water well construction and methane migration are longstanding issues in Pennsylvania.
Gas drilling has recently boomed in Pennsylvania, Ohio and West Virginia.