Asbestos and man-made vitreous fibers as risk factors for diffuse malignant mesothelioma: Results from a German hospital-based case-control study

Background This study examines the role of occupational factors in the deve lopment of diffuse malignant mesothelioma with special emphasis on the dose -response relationship for asbestos and on the exposure to man-made vitreou s fibers (MMVFs). Methods One hundred and twenty-Jive male cases, diagnosed by a panel of pat hologists, were personally interviewed concerning their occupational and sm oking history. The same number of population controls (matched for sex, age and region of residence) underwent similar interviews by trained interview ers. Odds ratios (OR) were calculated for an expert-based exposure index us ing conditional logistic regression. Results Exposure to asbestos shows the expected sharp gradient with an OR o f about 45 for a cumulative exposure > 1.5 fiber years (arithmetic mean 16 fiber years). A significant OR was calculated even for the lowest exposure category "> 0-less than or equal to 0.15 fiber years". Although the mean cu mulative exposure to MMVF is roughly 10% of the exposure to asbestos, an in creased OR is observed in an ever/never evaluation. This observation is hea vily hampered by methodical problems. A corresponding case-control study wa s performed using a lung tissue fiber analysis in addition to interviews. B oth interviews and the lung tissue analysis yielded similar OR levels betwe en the reference and the maximum exposure intervals. Conclusions Despite a possible influence as a result of selection and infor mation bias, our results confirm the previously reported observation of a d istinct dose-response relationship even at levels of cumulative exposure be low 1 fiber year. Moreover the study confirms that asbestos is a relevant c onfounder for MMVF A causal relationship between exposure to MMVF and mesot helioma could neither be detected nor excluded, as in other studies. (C) 20 01 Wiley-Liss, Inc.