Drinking water wells near gas drilling activity in northern Pennsylvania registered higher levels of methane than wells farther from the drilling, a Duke University professor said.

Robert Jackson, Nicholas professor of Global Change at Duke, joined a West Virginia University professor of community medicine in traveling to the University of Pittsburgh Friday for the "Health Effects of Shale Gas Extraction" conference.

Earlier this year, Jackson released information he gathered while studying 68 private groundwater wells across five counties in northeastern Pennsylvania and southern New York. He said the data showed groundwater with higher levels of methane, particularly when located within a kilometer of a gas well.

Jackson emphasized, however, he and his team found no fracking chemical contamination in their water samples, as some suspected they would.

"Most problems are caused by companies that are in a hurry. When you are in a hurry, you make a mistake," he said.

Bill Burket, representing the Canonsburg, Pa.-based Marcellus Shale Coalition, said the industry is working to make drilling activity safer and healthier. The coalition represents many natural gas and oil companies, including Chesapeake Energy, Consol Energy, Range Resources, Chevron, Hess Corp., Exxon Mobil subsidiary XTO and Royal Dutch Shell.

"We are minimizing our environmental footprint with horizontal drilling," he said, noting the process allows gas companies to drain the same amount of fuel with one well that used to require many separate wells.

Burket also said coalition members have agreed to hire truck drivers with solid safety records, while many are also now using the closed-loop drilling system. This plan allows drillers to use less fresh water in drilling, while also having to dispose of less wastewater.

Charles Werntz, professor of community medicine at WVU, said he has seen various injuries suffered by those working on gas drilling sites, ranging from head trauma to amputations.

"We are seeing injuries from workers slipping from the drilling apparatus," he said, noting, "You could find this at any industrial site."

Werntz also said information from the drilling industry shows they use about 5.6 million gallons of water, sand and chemicals to frack a well. If the 0.5 percent of this solution consists of chemicals, as drillers note, that means 28,000 gallons of chemicals are being pumped into the earth at high pressure.

Regarding problems with heavy trucks traveling on narrow, rural roads in West Virginia, he Werntz added, "The roads are straight and long in Oklahoma."

Bernard Goldstein, professor emeritus of environmental health at the University of Pittsburgh, said government and the public should not treat all drillers the same.

"Some companies are being proactive by releasing information, while others are not," he said.

Goldstein added, "with a little regulation and pressure, you can get the industry to do things."