The U.S. Environmental Protection Agency finalized new rules last week that clamp down on 27 states whose power-plant emissions dirty the air of their neighbors.

The new rules will cut hundreds of thousands of tons of “smokestack emissions,” according to the EPA.

“If you have a child with asthma or a loved one at risk of a heart attack, you can breathe easier today, because these new protections will decrease the chances they will end up in the emergency room,” said Mary Anne Hitt of The Sierra Club’s National Coal Campaign.

Known asthe Cross-State Air Pollution Rule,the new rule requires significant reductions in sulfur dioxide and nitrogen oxide emissions that cross state lines. Both pollutants acts in the atmosphere to form particle pollution that is easily transported long distance by air.

All of the states affected by the new rule are in the Eastern sections of the United States (see graphic).

The EPA says the new rule will avoid as many as 34,000 premature deaths annually, as many as 19,000 hospital and emergency-department visits and more than 420,000 cases of upper and lower respiratory symptoms each year.