air
...at are harmful to human health, welfare, animal or plant life, or property. In the past with air pollution we included mainly the outdoor pollutants, although in recent years this is not the case. Today we separate pollutants in to two categories. Primary pollutants, because they come directly from various sources, and secondary which are by-products of chemical interactions of the primary pollutants within the atmosphere. Particulates Although air pollution might be thought of as unwanted gases in the atmosphere, two of five primary pollutants are really solid substances called particulates. Soot has always been a sure indicator of a polluted atmosphere, but other than soiling and a negative psychological effect, soot can't settle into the lungs and cause serious diseases. Thick ,black smoke coming out of a stack is that what we think causes the pollution, but what really creates the damage is what we can't see. Particles like this are called suspended particles. They come from many incomplete burning and can consist a variety of substances. The m...