What are the criteria pollutants addressed under the Clean Air Act?

The criteria pollutants defined under the Clean Air Act consist of a set of air pollutants that are considered harmful to public health and the environment. The correct grouping identifies these pollutants as Particle Pollution (particulate matter), Ground Level Ozone, Carbon Monoxide, and Sulfur Oxides.

Particle pollution refers to fine particles that are small enough to be inhaled and can cause respiratory issues and other health problems. Ground level ozone, formed by chemical reactions between volatile organic compounds (VOCs) and nitrogen oxides in the presence of sunlight, can lead to significant health effects, particularly for those with pre-existing respiratory conditions. Carbon monoxide, a colorless odorless gas, can be harmful when inhaled in large amounts because it prevents oxygen from entering the body's cells and tissues. Sulfur oxides are gases that result from the combustion of fossil fuels containing sulfur, leading to respiratory problems and contributing to the formation of acid rain.

Each of these pollutants has established National Ambient Air Quality Standards (NAAQS) set by the Environmental Protection Agency (EPA) to protect public health and the environment.