Company-Level, Semi-Quantitative Assessment of Occupational Styrene Exposure when Individual Data are not Available

Abstract

In epidemiological research, self-reported information about determinants and levels of occu-pational exposures is difficult to obtain, especially if the disease under study has a high mortality rate or follow-up has exceeded several years. In this paper, we present a semi-quantitative exposure assessment strategy for nested case–control studies of styrene exposure among work-ers of the Danish reinforced plastics industry when no information on job title, task or other indicators of individual exposure were readily available from cases and controls. The strategy takes advantage of the variability in styrene exposure level and styrene exposure probability across companies. The study comprised 1522 cases of selected malignancies and neuro-degenerative diseases and controls employed in 230 reinforced plastics companies and other related industries. Between 1960 and 1996, 3057 measurements of styrene exposure level obtained from 191 companies, were identified. Mixed effects models were used to estimate expected styrene exposure levels by production characteristics for all companies. Styrene exposure probability within each company was estimated for all but three cases and controls from the fraction of laminators, which was reported by a sample of 945 living colleagues of the cases and controls and by employers and dealers of plastic raw materials. The estimates wer