The companies drilling at these sites employ a process called hydraulic fracturing, or "fracking," pumping water, sand, and chemicals deep underground at high pressure. This opens cracks that allow natural gas to flow into the wells. The process now accounts for about 15 percent of natural-gas production, and some estimates see it rising to nearly half of production by 2035.
Some homeowners in drilling areas believe fracking has polluted their drinking water. Our study suggests that some of them may be right, at least in terms of methane contamination. Our results are also relevant to the bigger question of what role shale gas and hydraulic fracturing should play in solving the nation's energy problems.
Natural gas, or methane, is not benign. It's flammable and potentially explosive. In very high concentrations, it can cause asphyxiation. However, there has been little research on its health effects in drinking water, and the federal government doesn't regulate it as a contaminant in public water systems.
So when someone asked us whether we'd drink water from the wells we studied, we thought for a moment and then answered that we would drink it once or twice, and maybe even occasionally. However, we wouldn't feel safe drinking it regularly, and we don't think the region's homeowners should have to.
Environmental scientists often have the unpleasant task of exposing the drawbacks of different technologies, and this study shows one downside of fracking. But other energy resources have drawbacks, too, and in some cases they're big ones.
Over the past two years alone, deepwater oil drilling led to a catastrophic spill in the Gulf of Mexico; an earthquake and tsunami triggered a nuclear disaster in Japan; and a flood of coal sludge inundated homes and spilled into a river in Kingston, Tenn.
Given such incidents, the conclusion we take away from our study is that the United States needs to focus on developing alternative, renewable energy resources that are greener and safer.
As President Obama stressed in a speech at a hybrid-vehicle technology plant in Indianapolis last week, there are many reasons to promote renewables. Enhance our energy security: check. Reduce our reliance on foreign suppliers: check. Reduce water and air pollution and global warming: check again.
Denmark now generates a fifth of its electricity from wind. China and Germany are creating jobs while producing solar power. Yet the United States continues to lag. We rank 17th worldwide in the clean-energy technology sector. Our green energy industries have been expanding at a rate of 28 percent a year since 2008, according to a new report commissioned by the World Wildlife Fund for Nature magazine. China's, by comparison, have grown 77 percent a year.
To be sure, renewables have their warts as well. Concentrated solar power takes land and lots of water, typically in places where water is scarce. Windmills kill birds and bats. But these issues are far more manageable than the water, air, and national security problems created by the energy resources we favor today.
We'll likely be using shale gas for some time, and the problems we've highlighted can probably be solved. It would be inaccurate and unfair to say our study proves that fracking should be banned.
Instead of just safer, though, we would like to see shale gas become largely unnecessary, along with coal and oil. The faster we develop and adopt renewable energy technologies, the less we will have to worry about whether it's safe for people to drink their water. We should all be able to raise our glasses to that.
Rob Jackson is a professor of global environmental change and Avner Vengosh is a professor of geochemistry and water quality at Duke University. Their study on hydraulic fracturing appears in the Proceedings of the National Academy of Sciences. They can be reached at firstname.lastname@example.org and email@example.com.