Officials say the Birmingham area's air-pollution rating is the best it has been in more than three decades.
The Alabama Department of Environmental Management says the region including Jefferson, Shelby and Walker counties has met a set of federal pollution standards for the first time in more than 30 years.
The state asked federal officials to certify that the area was in compliance, and the Environmental Protection Agency agreed.
Environmental officials say the improvements in air quality result from reductions in emissions mandated by government regulators.
A state environmental spokesman, Scott Hughes, says the decision makes it easier for industries to operate in the area, and the improvement in air quality reduces health risks for people living in the region.
Copyright 2013 The Associated Press.