What agency is responsible for setting air quality standards in the United States?

The agency responsible for setting air quality standards in the United States is the Environmental Protection Agency (EPA). This federal agency was established to protect human health and the environment by enforcing regulations based on laws passed by Congress, particularly the Clean Air Act. The EPA's role involves establishing and enforcing national air quality standards, which aim to ensure that air pollution does not pose a risk to public health or the environment.

The Clean Air Act mandates the EPA to set National Ambient Air Quality Standards (NAAQS) for pollutants considered harmful to public health and the environment. These standards are critical for managing air quality and guiding states in developing their air quality management plans.

Other options are associated with different regulatory functions. For instance, the Federal Aviation Administration oversees the safety of civil aviation, while the Occupational Safety and Health Administration is focused on worker safety and health standards in the workplace. The Department of Transportation manages national transportation systems but does not directly set air quality standards. Hence, the Environmental Protection Agency is specifically charged with the responsibility of maintaining and improving air quality across the nation.