American Journal of Epidemiology Vol. 144, No. 7: 623-633
Copyright © 1996 by The Johns Hopkins University School of Hygiene and Public Health
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Exposure to Styrene and Mortality from Nervous System Diseases and Mental Disorders
1Unit of Environmental Cancer Epidemiology, International Agency for Research on Cancer Lyon, France
2Department of Environmental Health, University of Washington Seattle, WA
3Department of Epidemiology and Public Health, Institut Municipal d'Investigació Mèdica Barcelona, Spain
4The Cancer Registry of Norway Oslo, Norway
5Department of Occupational Health, Karolinska Hospital Stockholm, Sweden
6Center for the Study and Prevention of Cancer Florence, Italy
7Centro di Documentazione per la Salute Bologna, Italy
8Medical Research Council Environmental Epidemiology Unit, University of Southampton Southampton, United Kingdom
9Istituto Nazionale per la Ricerca sul Cancro Genova, Italy
10Institute of Epidemiology and Social Medicine, University of Aarhus Aarhus, Denmark
11Danish Cancer Society Copenhagen, Denmark
12Finnish Institute of Occupational Health Helsinki, Finland
13Epidemiology and Medical Statistics Unit, Health and Safety Executive Bootle, United Kingdom
14Instituto Fisiologia Clinica Pisa, Italy
Reprint requests to Dr. M. Kogevinas, Department of Epidemiology and Public Health, Institut Municipal d'Investigació Mèdica (IMIM), 80 Doctor Aiguader Rd., Barcelona 08003, Spain.
Chronic low-dose exposure to solvents has been associated in epidemiologic studies with chronic neurotoxicity, but the evidence is not consistent. Styrene causes acute disturbances in the central and peripheral nervous systems. To determine if exposure to styrene may contribute to chronic diseases of the central nervous system, the authors examined mortality from nervous system diseases, mental disorders, and suicide in relation to styrene exposure in an international historical cohort study. The cohort involved 35,443 workers employed during 1945–1991 in the reinforced plastics industry, where high exposures to styrene occur. Indicators of exposure were reconstructed through job histories and environmental and biologic monitoring data Poisson regression was used for internal comparisons. Mortality from diseases of the central nervous system (27 deaths) increased with time since first exposure, duration of exposure, average level of exposure, and cumulative exposure to styrene. A quadratic model described best the dose-response shape for cumulative exposure and duration of exposure with the highest risks at around 300 ppm-years and 5 years, respectively, and a subsequent decrease in risk in the highest exposure categories. Mortality from epilepsy increased monotonically with all styrene exposure indicators, while associations for degenerative diseases of the central nervous system were generally weaker. Mortality from mental disorders and suicide decreased with increasing duration of exposure and cumulative exposure, while there was no trend with time since first exposure and average exposure to styrene. These findings suggest that, in addition to the known acute effects, exposure to styrene may contribute to chronic diseases of the central nervous system. Am J Epidemiol 1996;144:623–33.
central nervous system; cohort studies; mental disorders; mortality; occupational health; styrenes; suicide