As early as the 1950's Congress sought to improve the nation's air quality . However in the late 1960s with the Air Quality Act of 1967  and later with the Clean Air Act (CAA) of 1970 , Congress for the first time created a regulatory scheme designed to "reduc[e the] emissions of certain contaminants responsible for widespread air pollution problems" . Within this schema, the primary mechanism for regulatory control of air pollutants are the National Ambient Air Quality Standards (NAAQS) "which define levels of air quality that must be achieved to protect public health and welfare." . To complement the national standards, the 1970 Act also directed the creation of "State Implementation Plans" (SIPs) or guidance for the states to assist them in limiting specific source emitters . One of the last major provisions of the Act was the creation of New Source Performance Standards (NSPS) which were developed to to force the evolution of cleaner technologies in order to prevent any significant deterioration of air quality .