DECORAH, Iowa - During an exchange at a town hall Sunday night, Texas Gov. Rick Perry disputed the notion that hydraulic fracturing contaminates groundwater.

"We can have this conversation but you cannot show me one place, not one where there is a proven pollution of groundwater by hydraulic fracking," Perry said as he interrupted a questioner who claimed it did pollute water.

"That's false," a man in the audience shouted.

The controversial process involves the mixture of water, sand and chemicals inserted deep into the ground to enhance the productivity of oil and gas wells.

Perry held firm to his claim, saying there is no scientific proof hydraulic fracturing, also known as hydrofracking, has contaminated groundwater, and noted his home state of Texas has participated in the process for years.

"Bring me the paper, bring me the paper, show me the paper," Perry said. "I am truly offended that the American public would be hoodwinked by stories that do not scientifically hold up. If that was true, it would be on the front page of every newspaper. It would be on ABC, NBC, CBS, Fox News. Everybody would be running that story. We have been using hydraulic fracturing in my home state for years and this is a fear tactic that the left is using and the environmental community is using that absolutely, excuse the pun, does not hold water."

"Not true," an audience member said again.

"Bring me the evidence and once we do that, you show it to me, and I'll be the first to say you've got a point," Perry concluded, moving onto a question about states' rights.

On Dec. 9, the Environmental Protection Agency released a "draft" report implicating hydrofracking as causing ground water pollution in Pavillion, Wyo., the first major study finding such a claim. The Wall Street Journal released an editorial Sunday evening debunking the EPA's report, saying the study "is neither definitive nor applicable to the rest of the country," and much like Perry, the paper questioned the credibility of the EPA.

"The safety of America's drinking water needs to be protected, as the fracking industry itself well knows," the Wall street editorial read. "Nothing would shut down drilling faster, and destroy billions of dollars of investment, than media interviews with mothers afraid to let their kids brush their teeth with polluted water. So the EPA study needs to be carefully reviewed. "But the EPA's credibility is also open to review. The agency is dominated by anticarbon true believers, and the Obama Administration has waged a campaign to raise the price and limit the production of fossil fuels."

The campaign had no other comment on the exchange.

Perry's town hall in Decorah marked the fifth event on day four of his bus tour through Iowa, but the event at the historic hotel drew in several non-supporters willing to confront the Texas governor about controversial topics such as the ability of gays to serve openly in the military, a difference from his earlier event in New Hampton.