What is the primary source of air pollution in the United States?

The primary source of air pollution in the United States is automotive vehicles. This includes passenger cars, trucks, and buses, which collectively release significant amounts of pollutants such as nitrogen oxides (NOx), volatile organic compounds (VOCs), carbon monoxide (CO), and particulate matter (PM) into the atmosphere. The emissions from vehicles are especially impactful in urban areas where traffic congestion is prevalent, leading to increased levels of ground-level ozone and other harmful air quality issues.

Over the years, regulations have been implemented to reduce vehicle emissions, such as the Clean Air Act and subsequent amendments, which have contributed to cleaner air. However, despite improvements in technology and cleaner fuel options, automotive exhaust remains a significant contributor to overall air pollution due to the high number of vehicles on the road.

In contrast, while electric power plants, steel mills, and home heating systems do contribute to air pollution, they are not the predominant source when considering the total emissions across the country. Electric power plants predominantly contribute to sulfur dioxide (SO2) and carbon dioxide (CO2) emissions, steel mills primarily emit particulate matter and other industrial pollutants, and home heating systems, while they can contribute to air quality issues particularly with outdated systems, represent a smaller fraction of the total emissions compared