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.
Bloomberg News reports that a federal government researcher says sand dust from hydraulic fracturing to extract natural gas from rock is one of the biggest threats to workers at drilling sites.
About 80 percent of air samples from well sites in five states exceeded recommended limits for silica particles, said Eric Esswein, an industrial hygenist at the National Institute for Occupational Safety and Health.
The dust particle can lodge in the lungs and cause potentially fatal silicosis, he said at a Monday conference.
Drilling companies and workers need to do a better job dealing with sand particles, he said.
The companies do a better job dealing with toxic chemicals at drilling sites, he said.
Esswein's team visited well sites in Texas, Colorado, Arkansas, North Dakota and Pennsylvania in 2010-2011.
"There is a big focus on safety at well sites," he said. "There isn't as much emphasis on health. We call it the big S and the Little H."