Prior to the signing of the Clean Air Act (1970), air pollution regulations in the United States were considered the domain of local or state government officials.

Common sense suggests the rational underlying this legislative history. For over one hundred years the United States had a relatively small population inhabiting a relatively large land mass. The predominantly agricultural nature of the society meant that air pollution issues involved excess smoke from burning fields and clearing forests. Those types of air quality issues perhaps temporarily affected neighboring communities and prevailing wind patterns normally solved the problem within a short period of time.

As the population moved west and into the industrial era, the amount of land and people exposed to increased dirty air emissions from smokestacks expanded exponentially. The first government regulations to deal with emissions from stationary sources came from city and county governments. Federal government regulations dealing with air quality problems officially started in 1955, with the passage of the Air Pollution Control Act. During this time the federal government conceptualized their role as ancillary to the states and the Act followed that philosophy by creating a fund to aid states in their efforts. Substantive action, however, was slow to follow because of the minimal amount of state regulation and enforcement in the area.

Social unrest during the 1960s created an atmosphere conducive to increased social problem solving on a national scale. While civil rights and social welfare programs arguably received the greatest amount of attention, environmental issues were also moving their way to the forefront of the policy making agenda. Scientific studies linking air pollution to health issues and the logic of transboundary pollution moved public opinion enough to move Congress into action.

Starting with the Clean Air Act of 1963 (the precursor to today's Clean Air Act) Congress began funding air quality research programs as well as continuing financial assistance for state activities. In 1967 they passed the Air Quality Control Act, which among other things, organized the country in Air Quality Control Regions and established a system for defining Ambient (outdoor) Air Quality Standards for states wishing to set standards limiting emissions. The stage was set for the move to a larger federal role in air quality management.

The Clean Air Act of 1970 (CCA) introduced the American population to the idea of a nationally directed air quality management program. CCA, twice amended (1977 and 1990) is among the most complex and ambitious pieces of federal legislation dealing with any environmental issue. The reasons are obvious. Air pollution issues cover a wide array of topics from dust and smog to acid rain and ozone depletion. Air pollution sources are equally vast, ranging from the lawn mower you use on a Saturday morning to the jet skis you use on a Saturday afternoon at the beach or lake and the automobile you use to drive you there. Electricity generation, factory production, mining and most every industrial activity contributes potentially harmful emissions into the air.

The Clean Air Act is a dual purpose piece of legislation. Its first and foremost goal is the protection of public health from pollutants that find their way into the air. The secondary goal is the protection of public welfare, generally defined as maintaining visibility levels and limiting air pollution effects on the environment, including agricultural products and buildings. To achieve these goals the Environmental Protection Agency establishes National Ambient (outdoor) Air Quality Standards (NAAQS), which are scientifically determined maximum amounts of pollutants that can be in the air prior to their causing health problems. Secondary NAAQS are set to protect public welfare. Six common air pollutants, called criteria pollutants are subject to regulation: ozone, volatile organic compounds (VOCs), nitrogen dioxide, carbon monoxide, particulate matter and sulfur dioxide.

Another category of pollutants less wide-spread throughout the United States, called Hazardous Air Pollutants (HAPs) are also regulated. Currently the EPA lists approximately 188 HAPs, with two of the most commonly know substances being mercury and benzene. It should also be noted that statistical analyses are used to determine NAAQS and they represent levels of particular substances that are found to cause harm to the average statistical person. There may be many individuals who are affected by either lower or greater amounts of any pollutant. The process for setting primary NAAQS has always been controversial because the CCA requires they be set with regard to health considerations only, rather than economic considerations. However, there is always a bit of misunderstanding in reading that requirement. States assume the primary responsibility for implementing NAAQS and with the help of the EPA they can choose among the least costly means available to achieve their goals.

Substantively, the controversy centers on the concept of technology forcing. Industry has consistently been opposed to the idea of their being required to come up with new technologies as the means for meeting air quality standards. Automobile manufacturers, for example, were opposed to the idea of having to design catalytic converters as a means of achieving emissions reductions called for when the CCA was originally passed.

Through its many revisions, the underlying structure of the Clean Air Act has followed the above outlined framework. The federal government (Congress and the EPA) sets standards and states assume responsibility for implementation. Both states and the federal government assume enforcement responsibilities.