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.
In a new study, researchers from the Colorado School of Public Health say that air pollution from hydraulic fracturing or fracking for natural gas may contribute to acute and chronic health problems for those living natural gas drilling sites.
"Our data show that it is important to include air pollution in the national dialogue on natural gas development that has focused largely on water exposures to hydraulic fracturing," said Lisa McKenzie, lead author of the study and a research associate at the Colorado School of Public Health.
The study found a number of potentially toxic petroleum hydrocarbons in the air near wells. That includes benzene, ethylbenzene, toluene and xylene.
Other chemicals found include heptane, octane and diethylbenzene, but information on their toxicity is limited, the study said.
The problems faced by those living close to wells being drilled include eye irritation, headaches, sore throat and difficulty breathing.
The three-year study focuses on Colorado's Garfield County.
Click here to learnmore about the Colorado study.