Carbon Monoxide

Health Effects: Carbon monoxide enters the bloodstream through the lungs and reduces oxygen delivery to the body's organs and tissues. The health threat from carbon monoxide at low levels is most serious for those who suffer from cardiovascular disease, such as angina pectoris. At much higher levels, carbon monoxide can be poisonous. Even healthy people may be affected. Visual impairment, reduced work capacity, reduced manual dexterity, poor learning ability and difficulty in performing complex tasks are all associated with exposure to carbon monoxide.

Sources: Motor vehicles produce about 60 percent of carbon monoxide nationwide; in cities, it may be as high as 95 percent. Other sources include industrial processes, non-transportation fuel combustion, and wildfires.