Originally aired June 16, 2010, NPR's All Things Considered, heard weekdays from 4:00 - 6:00pm.

Two years ago, Pennsylvania opened the door to a natural gas drilling technique that's caused controversy in some Western states. At the time, environmentalists worried that high-volume hydrofracking could contaminate water supplies, but the state and industry insisted that fracking was safe. Now, after a spate of accidents, Pennsylvania regulators are tightening up the rules governing fracking.

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