Carbon monoxide

Carbon monoxide is a colorless and odorless gas, formed when carbon in fuel is not burned completely. High concentrations of CO generally occur in areas with heavy traffic congestion. In cities, as much as 95 percent of all CO emissions may come from automobile exhaust. Other sources of CO emissions include industrial processes, non-transportation fuel combustion, and natural sources such as wildfires.

   Ozone

     Ozone can be good or bad. It all depends on where it is. Ozone is good when it is high up in our atmosphere. It protects us from sunburn. Ozone is bad when it is near the ground where we can breathe it in. It is formed when chemicals coming out of cars and factories Ground-level ozone is the primary constituent of smog and continues to be a pollution problem.

   Lead

Automotive sources & industrial processes, primarily metals processing, are the major source of lead emissions to the atmosphere.

Nitrogen dioxide is a reddish-brown, highly reactive gas that is formed in the ambient air through the oxidation of nitric oxide (NO). Nitrogen oxides (NOx), the term used to describe the sum of NO, NO2, and other oxides of nitrogen, play a major role in the formation of ozone, particulate matter, haze, and acid rain.

   Particulate matter

Particulate matter is the general term used for a mixture of solid particles and liquid droplets found in the air. Some particles are large enough to be seen as dust or dirt.

   Sulfur dioxide

Sulfur dioxide mostly comes from the burning of coal or oil in power plants. It also comes from factories that make chemicals, paper, or fuel. Like nitrogen dioxide, sulfur dioxide also reacts in the atmosphere to form acid rain