Construction groups say final rule could raise costs of power and materials. 

Updates on projects and companies in the Mountain States region.

Proposed designations could mandate added preconstruction permitting for some types of projects.

Cement and steel producers in some states would be included under U.S. Environmental Protection Agency's proposed rule.

A Canadian company’s “smog-eating” highway noise wall technology, aimed at trapping air pollutants emitted by vehicles, is currently being tested on highways in Toronto and the U.K. Proponents say it can reduce overall air pollution by 50%.