Which of the following is included in the list of hazardous air pollutants?

Benzene is classified as a hazardous air pollutant due to its toxicity and potential to cause serious health effects. It is a colorless, flammable liquid with a sweet odor and is known to be a byproduct of burning coal and oil, as well as a component of gasoline and tobacco smoke. Long-term exposure to benzene is linked to harmful effects such as blood disorders, including leukemia.

In contrast, ozone, while a significant air pollutant and a component of smog, is not listed as a hazardous air pollutant under the Clean Air Act because it occurs naturally in the atmosphere and is beneficial in the upper atmosphere. Particulate matter, although it poses serious health risks, is generally classified under more specific regulations rather than as a single hazardous air pollutant. Carbon dioxide is primarily known as a greenhouse gas and, while it contributes to air quality issues, it does not fall under the hazardous air pollutants as defined by the EPA. Thus, benzene stands out as the clear example of a hazardous air pollutant based on its specific health risks and regulatory classification.