With Pennsylvania becoming the newest focal point for natural gas drilling in the Marcellus Shale, municipalities like Philadelphia could see their water supply impacted by the chemicals injected into the natural gas wells. That's why Temple environmental engineer Michel Boufadel is calling for environmental impact studies on the drilling. "The idea of assuming that whatever they inject would never come up is really not scientific," says Boufadel. "Everything that exists in the literature tells us that's not the case — that you cannot ensure it will not come up."