Adjustment for the confounding effect of cigarette smoking in an historical cohort mortality study of workers in a fiberglass manufacturing facility.

In 1986 a statistically significant lung cancer SMR based on U.S. white male national mortality rates was reported for male fibrous glass workers for follow-up through 1982 of a cohort of U.S. man-made mineral fiber workers. The Newark, Ohio, plant of Owens-Corning, which comprised 38% of the fibrous glass workers in that cohort, also exhibited a statistically significant lung cancer standardized mortality ratio based on U.S. white male mortality rates. A case-control study of the Newark workers demonstrated that a history of cigarette smoking and not exposure to respirable glass is the most important factor in lung cancer risk for workers at the Newark plant. We provide an estimate of the extent of confounding by cigarette smoking for the Newark plant nationally based lung cancer standardized mortality ratio with data not previously available and which suggests that adjusting for the confounding effect of cigarette smoking could reduce the lung cancer standardized mortality ratio to a non-statistically significant level.