RADIOGRAPHIC SILICOSIS AND LUNG-CANCER RISK AMONG WORKERS IN ONTARIO

A case-control study nested in a cohort of workers under surveillance for silicosis in 1979 or later was undertaken to assess lung cancer ri sk in relation to the ILO coding scheme for the pneumoconioses. The su bjects of this study are from the 41 matched quartets, consisting of o ne worker with silicosis and three age-matched controls, in which a lu ng cancer case was diagnosed The adds ratio for lung cancer among subj ects with ILO classification 1/0 or more, in comparison to subjects wi th category less than or equal to 0/1, was 3.27 (95%CI = 1.32-8,2). Ad justment of the radiographic risk for the effect of cumulative radon e xposure had the effect of increasing the odds ratio for the associatio n between ILO category greater than or equal to 1/0 and lung cancer. A lthough small smoking differences could account for the increased lung cancer odds ratio among workers with silicosis, the empirical evidenc e suggests that these smoking differences do not exist. It is conclude d on the basis of two North American studies of silica exposed workers that radiographic silicosis is a marker for an increased risk of lung cancer Am. J. Ind. Med. 34:244-251, 1998. (C) 1998 Wiley-Liss, Inc.