Which of the following pollutants are regulated under the Clean Air Act?

The Clean Air Act establishes a regulatory framework for various pollutants that affect air quality. Among the substances mentioned in the options, carbon monoxide and sulfur dioxide are specifically identified under the National Ambient Air Quality Standards (NAAQS), which are established to protect public health and the environment.

Carbon monoxide is a colorless, odorless gas produced primarily from fossil fuel combustion, and it can have significant adverse health effects, particularly in high concentrations. Sulfur dioxide, on the other hand, is a significant contributor to acid rain and can cause respiratory problems and other health issues. Both of these pollutants have been determined to be harmful enough to require regulation, making them subject to specific standards under the Clean Air Act.

In contrast, while other pollutants listed, such as ozone and methane, are also important and may be regulated under different contexts within the Clean Air Act, they are not classified under the same categories with the broad public health protections that apply to carbon monoxide and sulfur dioxide. Therefore, focusing on carbon monoxide and sulfur dioxide highlights their specific regulation and the well-established standards in place for these pollutants under the Clean Air Act.