What is air pollution?

Air pollution is the contamination of the atmosphere by substances at concentrations harmful to human health, other living organisms, or the environment. These pollutants can be solid particles, liquid droplets, or gases and originate from both natural sources (volcanic eruptions, wildfires, dust storms) and human activities (vehicle emissions, industrial processes, power generation, agriculture). Primary pollutants are emitted directly into the atmosphere, such as carbon monoxide from vehicle exhaust or sulfur dioxide from coal-burning power plants. Secondary pollutants form when primary pollutants react with atmospheric components—for example, ground-level ozone forms from reactions between nitrogen oxides and volatile organic compounds in the presence of sunlight. Air pollution causes respiratory diseases, cardiovascular problems, and premature death in humans, while also damaging ecosystems, reducing crop yields, and contributing to climate change.