The Obama administration on Wednesday announced a long-delayed environmental regulation to curb emissions of ozone, a smog-causing pollutant linked to asthma, heart disease and premature death. The sweeping regulation, which are aimed at smog caused by power plants and factories across the country, particularly in the Midwest, is the latest in a series of Environmental Protection Agency controls on air pollution that wafts from smokestacks and tailpipes. Such regulations, released under the authority of the Clean Air Act , have become a hallmark of President Obama’s administration. Environmentalists and public health advocates have praised the E.P.A. rules as a powerful environmental legacy. Republicans, manufacturers and the fossil fuel industry have sharply criticized them as an example of costly government overreach. The National Association of Manufacturers has called the proposal “the most expensive regulation ever.” The proposed regulation would lower the current threshold for ozone pollution to a […]