U.S. Department of Labor investigations have uncovered hundreds of cases in which oil and gas workers, many involved in dangerous jobs, are being cheated of earnings.
An analysis by an environmental group finds hundreds of cases in which drillers used diesel fuel without obtaining permits and sometimes altered records disclosing they had done so.
The Government Accountability Office says environmental regulators are failing to adequately enforce rules for wells used to dispose of waste from drilling.
In Pennsylvania, opponents of gas drilling say regulators are slow and unprepared in responding to air quality complaints.
ProPublica surveys some recent research on potential health implications of hydro fracking.