大気汚染の肺癌発生におよぼす影響の実験的研究, 特にガソリンエンジン排気ガス暴露

抄録

The increase in the standard population death rate from pulmonary cancer warrants attention. Three factors can be attributed to this increase: air pollution, cigarette smoking, and occupational exposure to carcinogens. The present paper reports on the results of a study of the relationship between air pollution and pulmonary cancer. Rats, mice, and hamsters were subjected to up to 12 months exposure to diluted gasoline engine exhaust containing 300±50ppm CO, 0.21ppm NO, 0.08ppm NO₂, 28ppmC hydrocarbon in the form of methane and 32ppb O₃. Further experimentation consisted of combined treatments with carcinogens-rats with diisopropanolnitrosamine, mice with ethylcalbamate, and hamsters with diethylnitrosamine to determine whether the incidence of tumors would increase. No animals exposed exclusively to exhaust gas diveloped pulmonary tumors, indicating that exhaust caused no lung tumorigenesis. However, the frequency of pulmomary tumors increased in animals subjected to combinations of exhaust and carcinogens. The incidence of malignant pulmonary tumors in the rats group exposed for 12 months to carcinogens only was 8.7%, while that in the group exposed to the combination was 30.3%, with the rates for mice 72.7% as against 91.7%, and for hamsters, 3.8% as against 10%. The results indicate that gasoline engine exhaust increases the development of lung tumors, and that exhaust plus other carcinogens significantly increases the risks.