1990 was the most recent amendments to the act under President George H.W. Bush. The 1990 amendments granted significantly more authority to the federal government than any prior air quality legislation. Nine subjects were identified in this amendment, with smog, acid rain, motor vehicle emissions, and toxic air pollution among them. Five severity classifications were identified to measure smog. To better control acid rain, new regulatory programs were created. New and stricter emission standards were created for motor vehicles beginning with the 1995 model year. The National Emission Standards for Hazardous Air Pollutants program was created to expand much broader industries and activities.