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How does the United States Clean Air Act work to improve air quality?

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Dense smog and orange haze blanket the skyline of Mexico City at sunset, with buildings in the Polanco neighborhood partially obscured by air pollution. — air pollution Pollution darkening the skies over Mexico City.

The United States Clean Air Act (CAA) works to improve air quality by empowering the Environmental Protection Agency (EPA) to establish national air quality standards for six key pollutants: sulfur dioxide, nitrogen dioxide, particulate matter, carbon monoxide, ozone, and lead. States and cities must meet these National Ambient Air Quality Standards (NAAQS) or face penalties. The CAA also sets emission standards for new facilities and regulates hazardous air pollutants, contributing to significant reductions in overall emissions and improvements in public health.12