Risk assessment of different classes of workers in regard to lung cancer incident rate was computed according to respective geometric mean of cumulative exposures. Risk of lung cancer incidence for smokers according to the geometric mean of cumulative exposures 0.14, 1.42, 10.98 and 53.68 fiber/ml-yr for various cumulative exposure ranges, were projected 0.4, 4.06, 31.37 and 153.37 excess lung cancer per thousand exposed, respectively. Corresponding risk of lung cancer for groups of nonsmoker workers were estimated tenfold lower than smoking workers. Generally, 59 percent of all workers from smoker and nonsmokers have excess risk of lung cancer more than one per thousand