In his Jan. 10 column in the Rocky Mountain News, Independence Institute analyst David Kopel significantly misstates the record on the environmental risks posed by the gas drilling technique known as hydraulic fracturing.

Using carefully culled quotations and selected statistics, Kopel asserts "indisputably false facts" in ProPublica's reporting.

In fact, it is his column that is indisputably misleading.

Kopel quoted a press spokesperson for New Mexico as saying the state had never compiled "numbers about groundwater contamination from hydraulic fracturing" -- the actual forcing of water into rock. He cites a similar remark from a Colorado official.

These are classic examples of framing a precisely tailored question to elicit a misleading response, much as the tobacco industry used to ask scientists whether smoking could be conclusively identified as a cause of lung cancer.

Here are the facts.

State and federal officials have identified what several said was an alarming pattern of water contamination in and around drilling sites across the country. Until ProPublica began asking questions last year, few environmental officials had examined what role hydraulic fracturing may have played in this contamination.

Colorado records (PDF) cite some 1,500 cases from 2003 to 2008 in which drilling companies reported a hazardous spill, with 300 instances leading to what state officials determined was a measurable impact on water supplies. A tally of Colorado data was performed by the advocacy group Oil and Gas Accountability Project.

In New Mexico, Mark Fesmire, director of the Oil and Gas Conservation Division, said his state had documented some 800 cases in which water has been contaminated by oil and gas operations, half of them from waste pits that had leaked chemicals into the ground.

As ProPublica has reported, it's difficult for scientists to say which aspect of drilling -- the hydraulic fracturing, the waste water that accidentally flows into the ground, the leaky pits of drilling fluids or the spills from truckloads of chemicals transported to and from the site -- causes such pollution.

Here's why: The industry has adamantly refused to make public the ingredients of the chemicals it forces into the ground and later stores in the waste pits near drilling sites. Scientists say that information is crucial to tracing the source of pollution. Without those data, environmental officials say they cannot conclude with certainty when or how certain chemicals entered the water.

Ask officials in New Mexico and Colorado: Are there any cases in which we can prove beyond a reasonable doubt that hydraulic fracturing caused water contamination? Answer: No, we've never studied that question.

Ask those same officials: Are there hundreds of cases of water contamination in drilling areas, the vast majority of which use hydraulic fracturing? Answer: Yes.

The drilling industry, echoed by Kopel, cites three documents when asserting the environmental safety of hydraulic fracturing. They are a 2004 EPA study (PDF), a 2002 survey of state agencies (PDF) by the Interstate Oil and Gas Compact Commission and a similar survey in 1998 by the Ground Water Protection Council (PDF).

In its Nov. 13 article, ProPublica detailed flaws in the EPA study and reported that the two surveys were "anecdotal," meaning that they included none of the basic data required to qualify as a scientific study. The "results" were drawn from questionnaires sent to state officials. ProPublica did misstate the date on one of these surveys, referring to it as more than a decade old when it had been published in 2002.