Environmental Exposures with Decreased Risks for Lung Cancer?

Abstract

The case for a decreased risk of lung cancer after exposure to environmental agents is evaluated using toxicological and epidemiological data. Experimental evidence demonstrates that exposure to substances which produce an inflammatory response in the lung, such as bacterial endotoxins, causes an increase in the secretion of inflammatory mediators and substances with a particular effect on tumour cells such as tumour necrosis factor (TNF). Other irritant agents, such as tobacco smoke, may also induce an activation of macrophages at low levels of exposure. Epidemiological evidence from several studies suggests that people exposed to dusts containing bacterial endotoxins have a lower lung cancer incidence than those who are unexposed. There are also some data suggesting that in certain ethnic groups, females smoking a small number of cigarettes/day, might have a lower risk for lung cancer than non-smokers. These data provide support for a hypothesis that low-dose exposures to some air pollutants might result in a decreased risk of lung cancer.