Sulfur dioxide at elevated concentrations can cause respiratory problems. It also can be a contributing component of acid rain. Toxic chemicals such as benzene, toluene and 1,1,1 trichloroethane , when present in the air that we breathe in elevated concentrations over time, can cause various health effects including birth defects, cancer and other health problems. Sources of toxic emissions include industrial processes, such as refineries and chemical manufacturers, small businesses such as printers and dry cleaners and automobiles. Cars and trucks are the main contributors.
Carbon monoxide interferes with the blood's ability to transport oxygen to cells and tissues.
Exposure to elevated levels of carbon monoxide can cause drowsiness, headaches and sometimes death. Carbon monoxide is particularly hazardous to those who have heart disease or pre-existing lung conditions. Lead is a heavy metal that persists in the environment for decades. Emissions from metal smelters are another source. Exposure to lead at high levels and over time can cause brain and other nervous system damage, particularly in children.