Smog is created by the chemical reaction of sunlight, nitric oxides (NOx) and volatile organic compounds (VOC's) in the atmosphere, which leaves airborne particles (called particulate matter and ground-level ozone. Nitric oxides are released in the exhaust of fossil fuel-burning engines and by idustrial activity. VOC's are vapors released from gasoline, paints, solvents, pesticides, and other chemicals. Mobile sources (mainly vehicles) and the electric power industry were responsible for 78 percent of annual NOx emissions
in in the United States in 2004 (see Figure 2). That same year, 99 percent
of US VOC emissions came from industrial processes
(including solvents) and mobile sources.
Smog is especially harmful for seniors, children, asthmatics, and people with heart and lung conditions such as emphysema, bronchitis, and [asthma]. It can inflame breathing passages, decreasing the lung's working capacity, and causing shortness of breath, pain when inhaling deeply, wheezing, and coughing. It can cause eye and nose irritation and dry out the protective membranes of the nose and throat and interfere with the body's ability to fight infection, increasing susceptibility to illness. Hospital admissions and respiratory deaths often increase during periods when ozone levels are high.
air pollution, transportation, climate change, industry