The authorities and responsibilities of the Environmental Protection Agency (EPA) derive primarily from a dozen major environmental statutes. This book provides a concise summary of one of those statutes, the Clean Air Act. It provides a brief history of federal involvement in air quality regulation and of the provisions added by legislation in 1970, 1977 and 1990. It also explains major authorities contained in the Act as well as key terms and references for more detailed information on the Act and its implementation.

The main objective of these updated global guidelines is to offer health-based air quality guideline levels, expressed as long-term or short-term concentrations for six key air pollutants: PM2.5, PM10, ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide. In addition, the guidelines provide interim targets to guide reduction efforts of these pollutants, as well as good practice statements for the management of certain types of PM (i.e., black carbon/elemental carbon, ultrafine particles, particles originating from sand and duststorms). These guidelines are not legally binding standards; however, they provide WHO Member States with an evidence-informed tool, which they can use to inform legislation and policy. Ultimately, the goal of these guidelines is to help reduce levels of air pollutants in order to decrease the enormous health burden resulting from the exposure to air pollution worldwide.