By definition, air is composed solely of gases, and thus these particles can be considered pollutants.
Some particles have a natural origin , and other are produced by humans .
Whatever their origin, particles in the atmosphere can cause problems. The most obvious problem is appearance. Soot and dust in the air look bad, and the particles eventually settle out of the air and accumulate on leaves, automobiles, and window sills. For many people, particulate pollution is also a significant health problem. Pollen can produce allergic reactions, and prolonged exposure to coal dust and finely powdered rock can produce lung diseases such as black lung and silicosis.