Epidemiological studies of styrene-exposed populations

The potential human carcinogenicity of styrene has been investigated mainly by epidemiological studies of occupationally exposed populations. Several cohort studies have suggested that workers exposed to styrene in the chemical industry have increased mortality from lymphatic and hematopoietic cancer. However, this finding has not been consistent and has not been reproduced in studies of reinforced plastics manufacturers, whose exposures to styrene are generally higher. The explanation for the observed associations may therefore be confounding by concomitant exposures to other chemicals such as benzene and butadiene, which are not used in the reinforced plastics industry. Despite their large size, the published studies of mortality and cancer incidence lack the statistical power to rule out an important hazard from long-term exposure to high (> 50 ppm) airborne concentrations of styrene. However, they indicate that any risk of cancer from lower levels of exposure is likely to be small.