WASHINGTON — The Obama administration is expected to release on Wednesday a contentious and 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 would aim at smog from power plants and factories across the country, particularly in the Midwest, would be 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.