The 2005 Energy Policy Act contained a nice loophole for natural gas companies, exempting a practice known as hydraulic fracturing or "fracking" from the Safe Drinking Water Act, thus allowing the companies to pump unspecified chemicals mixed with water into the ground in search of natural gas depsosits.  There's widespread concern--and not a little anecdotal evidence--that the practice is polluting drinking water supplies and wreaking environmental havoc all over the US. 

Environmental groups are pressuring Congress to take action and regulate fracking, which, obviously, industry is strongly against.  They argue that regulation should be--and is being--performed by the states, and any Federal regulation would be unduly burdensome. 

Considering that none of the states are paying particular attention to this issue, and that state budgets typically don't have the resources to enforce what regulations they have on their books, it would appear that the natural gas industry has been benefiting from artificially low operational costs for several years, not having to pay attention to any regulations whatsoever. 

For a quick audio story of the fracking issue, here's yesterday's NPR story.