Before the Clean Air Act, which pollutants were primarily of concern in boiler operations?

The choice identifying particulate matter, sulfur dioxide, and CO2 as the primary pollutants of concern in boiler operations before the Clean Air Act is accurate because these pollutants are closely associated with the combustion processes typical in boiler operation.

Particulate matter consists of microscopic solids or liquid droplets that are emitted during combustion. In boiler operations, this can arise from the burning of fossil fuels like coal or oil, making it a significant concern for air quality and respiratory health.

Sulfur dioxide (SO2) is another critical pollutant related to the burning of fossil fuels, especially those containing sulfur, such as coal. When these fuels are burned, they release sulfur dioxide, which can contribute to acid rain and other environmental concerns. This was particularly significant before regulations were put in place to limit emissions from industrial sources.

Carbon dioxide (CO2), while primarily known as a greenhouse gas and not traditionally considered a pollutant in the same sense as others, became a concern due to its association with climate change and global warming linked to combustion processes.

Together, these pollutants highlight the environmental and health impacts of boiler operations before the implementation of the Clean Air Act, which aimed to reduce emissions of harmful substances generated by industrial activities.