Air pollution has been a problem for years and has caused many infections and depletion of the natural environment. The most recognized depletion is the depletion of the stratospheric ozone layer. Pollution has caused this and has been reason for the increase in human health problems. Indoor air pollution and urban air quality are listed as two of the world's worst pollution problems in the 2008 Blacksmith Institute World's Worst Polluted Places report. Pollutants cans either be primary or secondary. Primary meaning they are usually substances directly emitted from a process, such as ash from a volcanic eruption. On the other hand, secondary pollutants are not emitted directly but are formed when primary pollutants react or interact. A good example would be many secondary pollutants that make up photochemical smog. Some pollutants can be secondary and primary at the same time. For this to happen, they both emitted directly and formed from other primary pollutants. 4% of deaths in the United States are due to air pollution according to the Environmental Science Engineering Program at the Harvard School of Public Health. Here are some pollutants produced by human activity and how they can be produced. • Sulfur oxides are produced by volcanoes and many other industrial processes. Due to coal and petroleum often containing sulfur compounds, combustion can cause sulfur dioxide. Its formula is SO2. • Nitrogen oxides are emitted from high temperature combustion like nitrogen dioxide. Nitrogen dioxide, NO2, is one of the most prominent air pollutants. • Carbon monoxide is a poisonous gas that is colorless, odorless, and non-irritating. It’s produced through incomplete combustion of fuel such as natural gas, coal or wood. Cities around the world with high exposure to air pollutants have the possibility of children living within them to develop asthma, pneumonia and other lower...