Aubrey Miller wasn't wearing shoes when he walked on stage.

He was wrapping up nine hours of highly technical talks about the latest studies of potential environmental and health impacts of unconventional natural gas development, and he went shoeless to emphasize his point: that it's easy to miss things.

"What's missing is the really profound issue here," said the senior medical adviser with the National Institute of Environmental Health and Safety.

He noted that the nation has some 52,000 unconventional gas wells, yet when he searched the literature for research, he found little. "How do we have no data on an enterprise of this magnitude?"

Nearly 200 people had gathered at the University of Pennsylvania last month for what one of the organizers, Trevor Penning, director of Penn's Center of Excellence in Environmental Toxicology, said was likely a first - a summary of the current science.

It wasn't pretty. Speaker after speaker spoke of gaps and uncertainties. Even when they had results to share, they cautioned that the conclusions were preliminary, the limitations many.

The monitoring, they said, has not kept up with the pace of development.

When it comes to air, Drexel University outdoor air-quality specialist Peter DeCarlo and some students spent a few weeks taking air samples in the drilling regions. But, he said, "we desperately need more measurements, and high-quality measurements . . . to understand what's going on."

When it comes to water, U.S. Geological Survey water-quality specialist Lisa Senior summarized a few limited studies and work in progress, but overall: "Do we know what the effects are? . . . The answer is still 'we don't know for sure.' "

Penning thought some of the strongest results came from studies described by Lisa McKenzie, a Colorado School of Public Health research associate.

One found an elevated risk for neurological effects among people living close to natural gas drilling. Another found a higher incidence of congenital heart defects in children of mothers living close to wells.

Similarly, comparing health-care use in Pennsylvania counties which have natural gas development with neighboring counties without it, Penn medicine professor Reynold Panettieri Jr. found "signals" of neurologic effects and decreased "normal newborn rates."

But as Penning noted, these were broad epidemiological studies. What's missing, so far, are "good exposure data to support cause and effect."

At one point, Joseph Minott, executive director of the Philadelphia-based Clean Air Council, left the auditorium, shaking his head. "If you live in the community, you don't have the answers," he said.

Instead, the communities have anecdotal reports - sickened livestock, dead pets, various human health maladies.

A residents' group, Breathe Easy Susquehanna County, is turning to citizen science. "Mediocre data is better than no data," wrote a group founder, Rebecca Roter, in a statement she sent because she couldn't attend.

So when Minott got to the podium, he was angry. He said health and environmental impacts "have not been a high priority" in the state. Studies are lacking, and "there seems to be little interest" by officials to provide funds.

As State Rep. Greg Vitali (D., Delaware County) noted earlier in the day, $2 million for investigating health problems from natural gas development was cut from the 2012 state natural gas law, Act 13.

As Penning pointed out later, science takes time. It costs money. "People who are living near this on a daily basis have what they preceive as real concerns . . . . But we have to make sure the answers we give them are credible and trustworthy."

Russell White, health science manager for the American Petroleum Institute, said new rules and technologies were making drilling safer. He said companies had been hydrofracking wells for "close to 50 years," and what's different now is that "the magnitude has changed. That's causing issues."

State and federal regulators said they were doing their best.

Still, Kurt Klapkowski, director of the Bureau of Oil and Gas Planning in Pennsylvania's Department of Environmental Protection, said, "I'm not going to sit here and say everything is perfect." He said the biggest challenge now was dealing with the highly contaminated wastewater from drilling.

"I'm impatient. I want answers," Penn's Panettieri said in concluding remarks. "But you can only get the right answers with the right questions and the right tool set."

"The problem we have is we don't know what we're looking for."

Or, if no one had known to look for Miller's shoes, they wouldn't have known they were missing.

"GreenSpace," on the environment and health, appears every other week, alternating with Art Carey's "Well Being."

215-854-5147 @sbauers