Cancer Incidence in Workers Exposed to Styrene in the Danish-reinforced Plastics Industry, 1968-2012

Background: Occupational exposure to styrene is widespread and has been suggested to be carcinogenic. The aim of this study was to investigate whether occupational exposure to styrene increases the risk of cancer, in particular lymphohematopoietic cancers. Methods: We established a study population of 72,292 workers employed in 443 small and medium-sized companies producing reinforced plastics 1964-2007 by utilizing several national registries, expert assessment, and worker survey data. We identified incident cancer cases from 1968 to 2012 in the national Danish cancer registry and computed standardized incidence rate ratios (SIRs) with 95% confidence intervals (95% CI) based on national rates. Results: Increasing SIRs of Hodgkin lymphoma, myeloid leukemia, and cancer of nasal cavities and sinuses were inconsistently associated with increasing duration of employment, early year of first employment, or styrene exposure probability. No such trends were observed for cancer of the esophagus, pancreas, lung, kidney, or urinary bladder, which have previously been associated with styrene exposure. Lung cancer showed an overall increased risk that decreased by duration of employment. Conclusion: Occupational styrene exposure may be associated with Hodgkin lymphoma, myeloid leukemia, and cancer of nasal cavities and sinuses. Further studies are needed to evaluate if the observed associations are likely to be causal.