The Environmental Protection Agency released far-reaching air pollution regulations Wednesday, 21 years after they were first mandated by Congress and six days after they were signed by the agency.

The rules require coal- and oil-fired power plants to lower emissions of 84 different toxic chemicals to levels no higher than those emitted by the cleanest 12% of plants. Companies have three years to achieve the standards, and EPA has made clear a fourth year and perhaps even more time are also available to them.

"We're delighted," says Janice Nolen of the American Lung Association. "After waiting 21 years, it looks like we may actually have a rule that will help to save 11,000 lives a year and reduce exposure all across the country to a bunch of really toxic substances."