California air quality regulators have adopted the nation's toughest emission standards for construction vehicles, which contributes close to 20% of the state's diesel pollution. An estimated 180,000 vehicles would have to be replaced or retrofitted with smog traps, filters or cleaner-burning technology beginning in 2010. The rules would be phased in through 2020 for fleets of large vehicles and 2025 for smaller equipment. The clean-air proposal was sought by health advocates but has been the focus of an intense lobbying campaign by the construction industry, which believes the new rules will have a damaging affect on California's economy. Larry Mantle talks with Mary Nichols, Chairwoman of the California Air Resources Board, and John Dunlap, consultant to the Coalition to Build a Cleaner California.