Chesapeake Energy Corp,the Oklahoma-based firm is the No. 1 driller in Ohio.
Rig Count Interactive Map by Baker Hughes, an energy services company.
Shale Sheet Fracking, a Youngstown Vindicator blog.
The Ohio Environmental Council, a statewide eco-group based in Columbus.
Earthjustice, a national eco-group.
People's Oil and Gas Collaborative-Ohio, a grass-roots group in Northeast Ohio.
Concerned Citizens of Medina County, a grass-roots group.
No Frack Ohio, a Columbus-based grass-roots group.
Fracking: Gas Drilling's Environmental Threat by ProPublica, an online journalism site.
Pipeline, blog from Pittsburgh Post-Gazette on Marcellus shale drilling.
Allegheny Front, environmental public radio for Western Pennsylvania.
Air and water pollution from gas and oil drilling moves across state lines, so the drilling should be regulated by the federal government, a Cornell University professor said.
Hydraulic fracturing or fracking releases benzene and ozone into the air and can pollute surface water, testified Robert Howarth, a critic of drilling and a professor of ecology and environmental biology.
Much more research is needed to determine whether hydraulic fracturing or fracking is a threat to human health and the environment, he said.
He was testifying today before the House Committee on Oversight and Government Reform, Bloomberg News reported.
At present, oversight of drilling falls largely on the states.
His view was opposed by officials of producing states including Pennsylvania and Okalhoma in prepared comments.
"The states are light years ahead of the federal government in terms of experience and know-how about their individual states and about the science and technique of hydraulic fracturing," said Michael Krancer, secretary of the Pennsylvania Department of Environmental Protection.
For Howarth's full comments, go to www.psehealthyenergy.org/resources/view/198909.