Abstract
Cancer of the stomach shows a characteristically high proportion in Japan. However, recently age ad justed death rate of lung cancer shows a marked increasing tendency. It is predicted that the death rate of lung cancer in man will become to the first ranking in 1990. The main causes of lung cancer are concerned to be cigarette smoking and some kind of foods. But, there is some recent concern that oxidant air pollutants such as O3 and NO2 also might be a contributing risk factor from some epidemiological data.
Here, we would like to discuss about the experimental data on effects of O3 and NO2 on lung tumor formation. These data show that O3 and NO2 increase incidence and multiplicity of lung tumors in mice. However, the data are not always statistically significant. Also it depends on experimental design whether ozone enhances or inhibits the development of lung tumors in mice. Similarly, ozone and nitrogen dioxide enhance lung colonization by cancer cells in jected intravenously following exposure to the air pollutants, whereas NO2 kills lung metastases if cells are in jected prior to exposure. Both ozone and NO2modulate the proliferation of pulmonary neuroendocrine cells, the precursor cells for small cell lung cancer. It is concluded that there is little evidence to implicate ozone or NO2 directly as pulmonary carcinogens, but that they might modify and influence the carcinogenic process in the lung.
