As it turns out, fracking doesn't necessarily pollute the water supply. But the wells used for fracking might.

The distinction matters because drilling companies know how to make wells more reliable, even if all the effects of the fracking process are not yet well understood. One of the biggest worries, for example, has been that the hydraulic fracturing of deep underground rock to release the natural gas within it could somehow cause that gas to leak upward and contaminate drinking water supplies many thousands of feet closer to the surface.

But a new study finds that this danger is oversold. In places where the water near fracking sites has been contaminated, the culprit has been faulty steel tubing inside the vertical wells that lead down to the shale, or weak cement in the casing around it.

Making sure the wells are built soundly is something that drilling companies, and state regulators, can do. In about 5 percent of wells, the cement is imperfect enough to carry the risk of internal leaks.Poor cementing was partly to blame for the BP oil spill in the Gulf of Mexico four years ago.

So states need strong standards for well construction -- to ensure, for example, that the cementing is done effectively, that there are plenty of layers of casing, that the well runs straight and has smooth sides, and so on. And states need enough trained inspectors to see that the rules are carefully followed.

The good news is that many states have been putting such rules in place. Pennsylvania, Wyoming and Texas have all strengthened their regulations since 2010. In just the past year and a half, eight other states have updated their well-integrity rules, and six more have changes in the works.

Knowing that water pollution isn't inevitable with fracking should help both critics and defenders of the technology come together to agree on well standards. It wouldn't make fracking problem-free -- there's still a need for the safe handling of wastewater, as well as the noise, light and other distractions that many well neighbors hate. But it allays worries about a possibly dangerous side effect of a business that increasingly provides the U.S. with a relatively clean and inexpensive fuel.

David Fuller's view

The technology continues to improve; effective regulation is in everyone’s interests; the world gets the energy it needs.

If Europe embraced responsible fracking, its economies would be more competitive and Putin would be brought to heel more quickly.