Antioxidant vitamins and prevention of lung disease.

Although the evidence for oxidative stress for air pollution in the human lung is fragmentary, the hypothesis that oxidative stress is an important, if not the sole, mechanism of toxicity of oxidizing air pollutants and tobacco smoke is compelling and growing. First, biochemical mechanisms have been worked out for oxidation of lung lipids by the gas phase of cigarette smoke, NO2 and O3. The oxidation of lung lipids can be prevented by both vitamins C and E. Vitamin C is more effective in preventing oxidation by NO2, and vitamin E is more effective against O3. Second, multiple species of experimental animals develop lung disease similar to human bronchitis and emphysema from exposure to NO2 and O3, respectively. The development of these diseases occurs over a near lifetime exposure when the levels of NO2 or O3 are at near ambient air pollution values. Third, isolated human cells are protected against oxidative damage from NO2 and O3 by both vitamins C and E. Fourth, the vitamin C level in the lung either declines on exposure to NO2 for short-term exposures or increases on chronic cigarette smoke exposure. The effects of cigarette smoking on serum vitamin C is apparently complex and may be related to the daily intake of vitamin C as well as smoking. Serum vitamin C levels may be poor indicators of lung demands when daily vitamin C intakes are above 100 mg/day. Fifth, vitamin C supplementation protects against the effects of ambient levels of air pollution in adults as measured by histamine challenge. An augmented response to histamine challenge may represent increased lung permeability brought about by air pollution. In experimental animal and human experiments, the amount of vitamin C or E that afforded protection was in excess of the current recommended dietary allowance. Although animal studies do not provide evidence for complete protection against NO2 or O3, they do illustrate that current recommended daily allowances are inadequate for maximum protection against air pollution levels to which over 100 million Americans are exposed. The problem of air pollution and its effects on humans is truly of global concern. Air pollution is not restricted to North America or Japan where it was first recognized, but is a major public health problem in Europe as well. When data are available, air pollution probably will be shown to be a major public health problem in all urban areas of the world.(ABSTRACT TRUNCATED AT 400 WORDS)