PITTSBURGH (AP) — New research on Marcellus Shale gas drilling in Pennsylvania may only add fuel to the debate over whether the industry poses long-term threats to drinking water. A paper published on Monday by Duke University researchers found that gas drilling in northeastern Pennsylvania did not contaminate nearby drinking water wells with salty water, which is a byproduct of the drilling. "These results reinforce our earlier work showing no evidence of brine contamination from shale gas exploration," said Robert Jackson, director of Duke's Center on Global Change and a co-author of the paper, which appeared online in the Proceedings of the National Academy of Sciences.