Outdoor Air
The American Lung Association estimates that air pollution costs the nation $40 billion to $60 billion a year. Since the mid-1950s, it has been shown that the air in large urbanized areas is a risk factor for lung cancer. (1-3) Collectively, the studies suggest that the increased incidence of cancer in cities is due to three factors: 1) more cigarette smoking by the people who live in cities; 2) increased exposure of nonsmokers to side-stream or passive smoke from lighted cigarettes; and 3) occupational exposures.

The following occupations, involved with ambient air pollutants, are risk factors for certain cancers. Gas production workers have a greater risk of getting lung cancer than those who rarely work in the gas production area, especially if they are exposed to the products of coal carbonization. Men working at coke ovens in United States steel factories have an excess of lung cancer compared to men working in other parts of the steel industry. This is directly related to the exposure to the emissions from the ovens. Roofers who work with hot pitch are exposed to large amounts of benzo(a)pyrene (BaP). They, too, have a higher risk of getting lung cancer. So the concentration of BaP is a significant factor in heavily polluted cities and contributes to the excess of cancer.

The numerous atmospheric contaminants are found in one of two forms: particulate form, in which the carcinogen adheres to small particles in the air, or vapor form, in which the carcinogen is in a gas form. A city's atmosphere contains more contaminants than the atmosphere of a suburb or rural area. Many of these contaminants have been shown to be carcinogenic in various animals. The carcinogens found in particulate form are more important than those in vapor form because they can remain in the air from four to forty days and consequently travel very long distances. Carcinogens in particulate form originate mainly from the burning of fuels. Contaminants in vapor form are derived from the release of aerosols from industrial activities, from car exhaust, and from natural sources.

City air pollution is derived from many sources. A large amount of the particulate carcinogens comes from the burning of any material containing carbon and hydrogen, including petroleum, gasoline, and diesel fuel. A list of more than 100 different particulates containing detected carcinogens has been compiled. (4) A great many more exist, but detection of additional carcinogens in low concentrations is difficult because existing instruments are incapable of doing so.

In order to have a means of discussing carcinogenic air pollution in a standard fashion, one chemical compound, benzo(a)pyrene (BaP) was chosen as the indicator because it is a very potent carcinogen. The problem with choosing this one substance as an indicator is that there is no correlation between the level of BaP in the air and the level of other known detectable carcinogens. For instance, car emissions (gasoline or diesel fuel), coal-fired electric power plants, and oil-fired residential furnaces have low levels of BaP. But forest fires, residential fireplaces, refuse burning and coal burning in older furnaces, and motorcycle emissions produce high levels of BaP. With the new laws from the U.S. Environmental Protection Agency, the level of BaP in cities has dropped dramatically, but permitted levels of other carcinogens have risen. Since the level of BaP does not correlate with other atmospheric carcinogens, a new standard should be devised. This new standard or index should be composed of some number of different carcinogens that would more accurately reflect the total atmospheric carcinogen level. This atmospheric carcinogen index would be much like the pollen count or the Dow Jones Average which is composed of a number of different pollens or stocks, respectively. No accurate statement can be made correlating the number of lung cancer victims and the level of BaP (currently used as the atmospheric carcinogen standard) because BaP levels have decreased while lung cancer cases have increased.