Benchmark Doses Based on Abnormality of WBC or Micronucleus Frequency in Benzene-Exposed Chinese Workers.

Objectives: The aim of the study was to calculate benchmark dose for chromosomal damage and reduced white blood cell (WBC) associated with exposure to benzene (BZ).
Methods: A group of 317 exposed workers and 102 controls were examined for WBC count and genotoxicity by micronucleus (MN) frequency. The cumulative exposure concentration of BZ was calculated by ambient air BZ concentration at worksites in conjunction with job type and associated service duration.
Results: MN frequency (P < 0.01) was higher and WBC count was lower (P < 0.01) in exposed workers on average than in the controls. MN frequency was a more sensitive than WBC; workers older than 30 were more susceptible to abnormal MN frequency and WBC count reduction than those younger than 30.
Conclusions: Benchmark dose estimates indicated that BZ exposure at levels below the current occupational exposure standard can induce genotoxicity and hematotoxicity.