Which substances are specially regulated in the Clean Air Act due to their adverse impact on human health?

Hazardous air pollutants are specifically regulated under the Clean Air Act because they pose significant risks to human health and the environment. These pollutants include a variety of harmful chemicals that can cause serious health problems, including cancer, respiratory issues, and other acute and chronic health conditions. The Clean Air Act aims to reduce the emissions of these pollutants to safeguard public health and improve air quality.

The identification and regulation of hazardous air pollutants are crucial because they can come from various sources, including industrial processes, vehicle emissions, and even some consumer products. By specifically targeting these substances, regulatory measures can be effectively implemented to minimize exposure and protect vulnerable populations.

Total suspended solids, volatile organic compounds, and large industrial sources, while important in the context of air quality, do not have the same level of targeted regulation under the Clean Air Act as hazardous air pollutants do. Total suspended solids primarily relate to air quality from a particulate matter perspective, volatile organic compounds are more broadly categorized under pollutants but do not have the same specific status as hazardous air pollutants when it comes to targeted regulation. Large industrial sources refer to categories of emission sources rather than specific substances and thus do not encapsulate the focused protection aimed at hazardous air pollutants.