The tens of thousands of new oil and gas wells that have popped up in the U.S. over the last decade—especially in the Rocky Mountain states—have created lots of air pollution. Much of it comes from the engines used to pump and compress the oil and gas or from leaks around the wells and pipelines. This air pollution makes skies smoggier, hazier, more toxic to breathe and alters the climate.

In New Mexico, some gas wells produce hydrogen sulfide, which smells like rotten eggs. At low levels, hydrogen sulfide can cause difficulty breathing and headaches. At high levels, it can be lethal.

In western Wyoming and metropolitan Denver, oil and gas drilling is linked to rising smog levels, haze in wilderness areas and national parks, and to climate change.

Earthjustice filed a lawsuit against the Bush administration to force it to update the air pollution regulations with modern, state of the art technology to minimize the pollution. The Obama administration inherited this lawsuit and quickly recognized that Earthjustice was right. So they settled the case and have promised to do a fresh review with an eye towards getting newer, cleaner technology into the field.