These particles are small enough to penetrate the respiratory system's natural defenses against air pollution. Then there are sulfur dioxide and nitrogen oxides. Sulfur dioxide and suspended particles are very hazardous when combined because they react and form acid sulfate particles. These particles are inhaled more deeply into the lungs and remain for longer periods than other particles. Not only do these allergens make it difficult to breathe, but also there is less oxygen generated in urban areas due to deforestation.
Urban dwellers fight a breathing battle everyday.
However, there has been much done to improve environmental conditions in the inner city of Milwaukee. Many factories in downtown Milwaukee relocated out of the state, lessening the suspended particulate matter in the air. Also, monies were spent on improving the air quality. However, there has not been a T.S.P. episode or sulfur dioxide exceedance since 1991. All sources of air pollution have been well monitored and controlled to make the environment more asthma- friendly.