Benzene risk assessment: does new evidence on myelodysplastic syndrome justify a new approach?

Epidemiologic findings play an important role in benzene risk assessment, which is utilized to guide the selection of recommended benzene exposure levels to prevent adverse health effects. For decades, excess leukemia risk, especially that in the Pliofilm (R) cohort, has been the focus of benzene risk assessment. While more stringent benzene standards, often <= 1 ppm, have been promulgated to protect workers from developing leukemia, recent epidemiologic studies have reported elevated risk of myelodysplastic syndrome (MDS). This report aims to examine whether the use of new data on MDS is scientifically warranted in future benzene risk assessments. First, we reviewed current benzene guidelines, regulations, and underlying risk assessments in developed countries. Second, we examined current epidemiologic literature on benzene and MDS, which identified seven studies with simultaneous measures of MDS risk and benzene exposure and 17 studies on MDS in populations potentially exposed to benzene. Next, we examined the potential of the MDS data to serve as the basis of future benzene risk assessments, by comparing its quality and risk estimates with those used in current benzene standards. We conclude from the current literature that there is strong evidence that MDS can be caused by benzene, and the MDS data from the pooled petroleum study should be further examined in future benzene risk assessments. We recommend that future MDS-based benzene risk assessment use total MDS as the endpoint, take into consideration the full exposure period, and examine a range of benzene exposure metrics, including the role of peak, intermittent benzene exposures.