Most of the time we don't recognize air pollution because much of it is invisible, but it still can be harmful.
Air pollution causes health problems, as well as structural and crop damage.
In the early 1970's, the United States Environmental Protection Agency ordered studies of the health effects of the six major air pollutants. Many scientists are continuing this research today. Each of these air pollutants affects the human body in a specific way and each can cause serious health problems. Personal sensitivity to each of these pollutants is also an important factor. Generally, higher concentrations of pollutants and longer exposure to that pollutant result in a greater chance that serious health problems can result.