The influence of radiation and nonradiation factors on the lung cancer incidence among the workers of the nuclear enterprise Mayak.

For the estimation of radiation lung cancer risk for a human being it is important to take into account different etiological factors because of the polyetiology of this disease. This work was the aim of a retrospective investigation ("case-control") of 500 workers of a nuclear enterprise that had been gamma-irradiated in a wide dose range and had had exposure to airborne 239Pu. One hundred sixty-two persons contracted lung cancer (morbidity), and 338 persons that had not fallen ill served as pair control. Eleven potential risk factors were evaluated using a logistic regression model, five insignificant factors were excluded, and the remaining factors were arranged (by odds ratio) in decreasing order: smoking > plutonium pneumosclerosis > plutonium incorporation in body > chronic obstructive pulmonary diseases (COPD) > decrease of body mass > external gamma-irradiation. The percentage of histologically confirmed adenocarcinoma among the nuclear enterprise workers was 74%, which is significantly higher than 33% among the population that did not work at the enterprise, particularly in the case of high (more than 11 kBq) plutonium incorporation by the nuclear workers. The localization of tumors in this cohort is more frequently in the lower and middle lung lobes and at the periphery. Each of the histological types of lung cancer has manifested a different degree of correlation with particular factors. The adenocarcinoma has the most frequent correlation with the radiation factors; the odds ratio for plutonium incorporation and plutonium pneumosclerosis is 2.9 (95% CI = 1.0-8.4); for external gamma-irradiation the odds ratio is 1.9 (0.99-3.5); the odds ratio for smoking is 4.3 (1.9-9.9). The squamous-cell carcinoma has the highest correlation with non-occupational factors: with smoking the OR is 6.8 (1.2-38.7), with the chronic obstructive pulmonary diseases the odds ratio is 3.9 (1.8-8.4), and with body mass decrease the odds ratio is 2.1 (0.94-4.6); odds ratio for plutonium incorporation is 4.2 (1.4-12.8). The small-cell carcinoma has correlation with body mass decrease [odds ratio = 2.9 (1.2-7.6)] and high level of smoking [smoking index > 500; odds ratio = 3.5 (1.4-8.9)]. The portion of the occupational cancers among the workers of the nuclear enterprise, evaluated on the base of attributive risk, is 26%, with 57% for adenocarcinoma, 9% for squamous-cell carcinoma, and 8% for small-cell carcinoma. The investigation is continued to assess the dose-effect and factors interactions.