Abstract
Recent epidemiological studies have demonstrated a slightly higher risk in the population of those, who were occupationally exposed to diesel exhaust particles (DEP), and some of the data have demonstrated a statistical significance (Table 4). Among several cohort studies, the large scale and long followed study by Garshick showed a significantly higher relative risk of 1.45 for all subjects and 1.72 for the population exposed for 17-17 years. Furthermore, his colleagues studied the exposure level for diesel particles in this occupational environment. When applying the equation relative risk=1+c×d×k (c: exposed dose, d: exposed years, k: coefficient), and when the obtained k value was applied to the annual lung cancer death by gender and age group in Japan, annual excess deaths by lung cancer were estimated to be 648.7 (243.2-1198.2) for the whole population of the country (Table 5), and a life time risk for 1 μg/m3 DEP exposure (unit risk) was estimated to be 4.16 (1.56-7.69)×10-4.
With the presumed average exposure levels of diesel particles in Tokyo, other cities and in the whole country, the obtained values from the three different calculations were compared (Table 6). The range of unit risk was calculated from the animal data overlapped with that from the epidemiological data, and the risk in Tokyo inhabitants showed a close but higher value than the risk from the epidemiological data. A contributing rate of diesel-related lung cancer to the total lung cancer and an annual risk in Japan were calculated from the animal data (Table 7). The standardized mortality ratios of lung cancer by prefecture in Japan were calculated, and a higher incidence of lung cancer in the prefectures, which include densely populated area were shown (Table 8).
Although uncertainties may be included in these calculations, it can be concluded that DEP may partly cause lung cancer in humans, especially who are living in urbanized area.
