There have been documented cases of leaking gas ruining nearby well water, of air pollution and of problems from the waste the drilling generates.

WSJ: Celebrity 'fractivists': True advocates or NIMBYs?

She outlined the reasons for a more cautious approach, which included the ban or moratorium placed on fracking in other countries, concerns cited by NI Water for the effect of pollution on water supply, and the dangers of well blowouts and earth tremors.

BBC: Hydraulic fracturing

In some places, the practice has been blamed for air pollution and gas leaks that have ruined well water, but the Obama administration and many state regulators say the practice is safe when done properly.

WSJ: Fracking coalition upsets both greens and drillers

In some places, the practice has been blamed for air pollution and gas leaks that have ruined well water, but President Barack Obama's administration and many state regulators say the practice is safe when done properly.

WSJ: Sierra Club blasts new plan to improve fracking