Advocates and researchers studying the influence of shale-gas drilling on health gathered in Philadelphia to discuss their work this week. The symposium was scheduled to coincide with the Shale Gas Insight Conference, which is also in town.

Some speakers seem convinced that hydraulic fracturing or "fracking" is hurting health in Pennsylvania. Others -- including Geisinger Health System researcher David Carey -- said the reports of health problems are, so far, largely anecdotal and "may be overblown." Carey said Geisinger is launching a long-term scientific study to get at the truth for people in Northeast Pennsylvania.

"So if -- and that's a definite if -- I'm not saying there are health impacts, some of them would show up fairly early," Carey said. "This is purely hypothetical, but let's say there was an impact on air quality, that could have an immediate effect on people that have asthma."

For other potential health concerns -- such as cancer or heart disease — it would likely take years to document links to the fracking industry, Carey said. He said the study will use Geisinger's digital records expertise and warehouse of electronic patient records to track health over time. Carey said a community group has pledged about $1 million to support the research.

Raina Rippel traveled from Washington County to discuss her work at the Southwest Pennsylvania Environmental Health Project. She said the group wants to help people protect their health, and is offering advice and tools.

One tool is a do-it-yourself water test kit. The low-cost tester alerts people to changes in a water-quality indicator called TDS, or total dissolved solids.

"If (the levels) are 500, 500, 500 -- then all of a sudden they spike to 2,000, that's the point when you know, 'Hey, something has happened, something has changed. I can stop drinking the water, I can stop bathing in it if possible. I can minimize my exposure to this water and I can get it tested,'" Rippel said.

The Southwest Pennsylvania Environmental Health Project is financed, in part, by the Heinz Endowments.

Looking beyond symptoms

The project is documenting health complaints from Washington County residents worried that their health problems are linked to the gas-drilling industry.

Rippel said many local doctors and hospitals only treat immediate symptoms.

"They are not going to ask necessarily ask, 'Why did this happen, and what is it that is potentially in your environment that might be causing that?' And that's where we step in," she said.

Michelle Bamberger and Robert Oswald presented finding from their research report "The Impacts of Gas Drilling on Human and Animal Health." The study was published in the journal "Scientific Solutions" early this year.

The researchers investigated reports of animal health problems associated with the fracking industry.

For more than 25 cases studies across eight states, Bamberger and Oswald gathered drilling activity information, as well as air, water and soil data, and also conducted interviews with animal owners and veterinarians.

In one case, from 2009 in Louisiana, 17 previously healthy cattle died about an hour after exposure to hydraulic fracturing fluid.

Bamberger said she hopes the findings on food and companion animals may eventually serve as a "sentinel" for humans.

"Not just what's happening to them, but what might happen to us," Bamberger said.

Bamberger said the most striking finding of the investigations was the difficulty in obtaining "definitive information" on the link between drilling and health problems.

She said many of the people her team tried to interview refused to talk because of non-disclosure agreements and ongoing litigation. There was also limited information on the chemicals used by the shale industry.