Abstract
The dose-response relationship in asbestos exposure and provoked malignancies inhumans has been reported during the last 10 years. however, the slope of the correlation equation varied widely among the authors. In order to clarify the reasons for the variation, 17 reports in the world were analysed focusing on the background factors which may influence the calculated risk.
The duration of follow up and the rate/number of workers dieing the follow up period, as well as the total number of subjects, are the most influential factors, and accuracy of measurement of exposed fiber concentration and of diagnosis of mesothelioma, may be the other significant factors. Different kinds of work seemed to correlate with the different physical or chemical nature of the fibers and to the resulting risks.
The 17 reports were scored according to each factor, and each report was evaluated by total score. Considering EPA re-calculation value in each report, it was concluded that in average, a 1% increase of lung cancer per 1 fiber·Eyear/m1 can be used as the risk coefficient in occupational asbestos exposure.
When this figure was applied to the population, and yearly lung cancer death by age in Japan, lifetime lung cancer risk due to ordinal asbestos concentration in environmental air was calculated to be 2-8×10-5 (male and female, smoker and non-smoker), and the annual risk to be 0.2-1.0×10-6. Lifetime risk of mesothelioma was also calculated, by using an average KM of 1.9, to be 11-53×10-4, and annual risk, 1-7×10-6, which is nearly the same as the annual death rate of the disease in Japan.
