The call to wean America off its addiction to foreign oil has become a mantra in U.S. politics, and help may be on the way. Recent advances in drilling technology have eased the process of extracting natural gas from shale rock. And Ohio, Pennsylvania, Michigan and West Virginia are among the states with large reserves of deposits of the relatively dense sedimentary rock; exploration is under way in more than 30 states. Some estimates put the U.S.'s potential natural-gas holdings as twice the size of Saudi Arabia's energy reserves. The new gas rush is producing a generation of "shale-ionaires" in areas gutted by the economic downturn. Northwest Louisiana, one of the poorest regions in the U.S., generated $6 billion in new household earnings last year, according to CBS. But the magic bullet comes with a major caveat: in the post-BP-spill age, when environmental concerns are no longer the province of just the progressive left, shale extraction has begun to come under fire. Critics say the EPA underestimates the damage natural-gas drilling does to our drinking water — a point made by some who live near gas wells, who have demonstrated the problem by showing that their drinking water is flammable.