California, particularly its south coast air basin, has suffered from air pollution since the early 1940s. Initially thought to be due to industrial waste gases, it is now recognized that 65% or more is due to motor vehicle tailpipe emissions. Although progress was made in controlling both industrial and mobile sources on a unit basis, the rapid increase in population (and motor vehicles) and industrial expansion made for an intolerable increase in the total air pollution problem. In 1968, the California Air Resources Board (CARB) was formed, and in 1976, the regional Air Quality Management Districts (AQMD) were formed. In 1988, the California Clean Air Act became law, and delineated responsibilities and authority of the CARB and the AQMD's. Significant progress has been made since, though the effects of a continually increasing population demand much more. The emissions control mandate of the CARB phasing low (LEV), ultra low (ULEV), and zero emissions (ZEV) vehicles into the new car sales picture by 2010 is having a major impact. Petroleum refineries are investing billions of dollars to produce gasoline to meet the LEV and ULEV standards; electric vehicles are being developed by several firms; alternate fuels and propulsion systems (such as the hydrogen fuel cell) are being investigated as possible means of meeting the requirements.