Which pollutants are regulated under the Clean Air Act (CAA)?

The Clean Air Act (CAA) regulates specific air pollutants known as criteria pollutants. These pollutants include carbon monoxide (CO), ozone (O3), sulfur dioxide (SO2), nitrogen dioxide (NO2), particulate matter (PM), and lead. The CAA establishes National Ambient Air Quality Standards (NAAQS) for these pollutants to protect public health and the environment. The identification and regulation of these specific criteria pollutants are rooted in extensive scientific research and data that link them to adverse health effects and environmental damage.

While greenhouse gases may be significant contributors to climate change and are subject to other regulatory frameworks, they do not fall within the traditional criteria pollutants defined under the CAA. Particles generated from construction activities and contaminants from agricultural operations can affect air quality, but they are not specifically regulated as criteria pollutants under the current CAA framework. Instead, these types of emissions might be addressed through other regulations or local ordinances. Thus, the criteria pollutants, such as carbon monoxide and ozone, are the substances that the Clean Air Act specifically regulates to ensure air quality standards are met.