The Obama administration is releasing new limits on ozone, the most widespread form of air pollution and the main ingredient in smog. Ozone, which is formed through a reaction of pollutants from power plants, factories and cars, has been linked to asthma, heart disease and premature death. U.S. restrictions imposed under President George W. Bush remain far looser than those in the European Union and Canada. Environmental groups have sued the Obama administration for tighter standards, prompting a court order to issue new draft regulations by December 1. According to The New York Times, the new rules would reduce the current threshold for ozone pollution from 75 parts per billion to between 65 and 70 parts per billion.