Clean Air Act
The primary federal law governing air quality in the United States, first enacted in 1963 and significantly amended in 1970 and 1990.
Detailed Explanation
The Clean Air Act (CAA) is the comprehensive federal law that regulates air emissions from stationary and mobile sources in the United States. Originally enacted in 1963, the law was dramatically strengthened by amendments in 1970, which established the EPA and introduced the National Ambient Air Quality Standards (NAAQS), and again in 1990, which added provisions for acid rain, ozone depletion, and toxic air pollutants. The CAA requires the EPA to set and enforce air quality standards, requires states to develop implementation plans to achieve those standards, and establishes emission standards for vehicles, factories, and power plants. It also created the permit system for major sources of pollution and the cap-and-trade program for sulfur dioxide that successfully reduced acid rain. The Clean Air Act has been one of the most successful environmental laws in US history. The EPA estimates that by 2020, the 1990 amendments alone prevented over 230,000 premature deaths annually and produced benefits exceeding costs by a ratio of more than 30 to 1. AirHistory's 10-year trend data reflects the ongoing impact of the CAA, aggregate pollutant levels and unhealthy air days have decreased significantly since the law's major amendments, though wildfire smoke and climate change now challenge some of that progress.
Related Terms
National Ambient Air Quality Standards (NAAQS)
EPA-established limits on concentrations of six criteria pollutants that must be met nationwide to protect public health and the environment.
EPA Air Quality System (AQS)
The EPA's national database of ambient air quality data collected from monitoring stations across the United States.
Nonattainment Area
A geographic area that fails to meet one or more National Ambient Air Quality Standards for a criteria pollutant.
Criteria Pollutants
The six common air pollutants regulated by the EPA under the Clean Air Act: ozone, PM2.5, PM10, CO, NO2, and SO2.
Frequently Asked Questions
The primary federal law governing air quality in the United States, first enacted in 1963 and significantly amended in 1970 and 1990.
The Clean Air Act (CAA) is the comprehensive federal law that regulates air emissions from stationary and mobile sources in the United States. Originally enacted in 1963, the law was dramatically strengthened by amendments in 1970, which established the EPA and introduced the National Ambient Air Quality Standards (NAAQS), and again in 1990, which added provisions for acid rain, ozone depletion, and toxic air pollutants. The CAA requires the EPA to set and enforce air quality standards, requires states to develop implementation plans to achieve those standards, and establishes emission standards for vehicles, factories, and power plants.
this entity is one of the U.S. air quality and pollution monitoring concepts that recurs across this site. The definition above is the technical answer; the paragraphs below add the practical context for how the concept connects to the the EPA Air Quality System (AQS) data behind every per-entity page on the site.
In the the EPA Air Quality System (AQS) data, this concept shapes one or more of the fields that drive the per-entity grades and rankings on this site. The methodology page describes which fields feed into which output; this glossary entry documents the underlying term.