A controversial method of drilling for natural gas, called fracking, has boomed in recent years—as have concerns over its potential to cause environmental contamination and harm human health. But a major review of the practice uncovered no signs that it is causing trouble below ground. \"We found no direct evidence that fracking itself has contaminated groundwater,\" said Charles Groat of the University of Texas, Austin, who led the study. The report, released at the annual meeting of the American Association for the Advancement of Science (which publishes ScienceNOW), doesn\'t give this form of natural gas extraction a clean bill of health. Rather, it suggests that problems aren\'t directly caused by fracking, a process in which water, sand, chemicals are pumped into wells to break up deep layers of shale and release natural gas. Instead, the report concludes, contamination tends to happen closer to the surface when gas and drilling fluid escapes from poorly lined wells or storage ponds. Grout, a former director of the U.S. Geological Survey, emphasized that the $380,000 report was independent from the natural gas industry and conducted only with university funds. Underlying white papers were peer-reviewed, he told ScienceNOW, and the Environmental Defense Fund was consulted on the overall scope and design of the study. As part of the review, 16 researchers at UT Austin, in fields ranging from air quality to hydrology, reviewed the scientific literature and regulatory documents for three major areas of fracking, in Texas, Louisiana, and Pennsylvania and New York. They could not find evidence of drilling fluids leaking deep underground, and methane in water wells in some areas is probably due to natural sources. The team did not see a need for new regulations specific to fracking, but for better enforcement of existing regulations of drilling in general—such as those covering well casing and disposal of wastewater from drilling. (Fracking in 2005 was specifically exempted from the Clean Water Act.)