Hematological changes among Chinese workers with a broad range of benzene exposures

Background Depression of peripheral blood cells is a well-known indicator of benzene hematotoxicity. Previous studies of its effects on specific types of blood cells have yielded inconsistent results. We examine hematological findings and their possible relations with exposure markers validated in a recent biomarker project conducted in Tianjin, China. Methods Personal benzene exposures were sampled with 3-M organic vapor monitors, and analyzed by gas chromatography. The peripheral blood cells were counted by a cell counter The WBC differential was manually counted on a total of 900 cells by a US commercial laboratory. Results A total of 130 exposed workers and 51 age- and gender-matched unexposed subjects were recruited in this study. Benzene exposure levels monitored on the day of biological sample collection for exposed workers ranged from 0.06 to 122 ppm. Their 4-week average and cumulative benzene exposure levels were 0.08-54.5 ppm and 6.1-623.2 ppm-years, respectively. Significant decreases of red blood cells (RBC), white blood cells (WBC) and neutrophils were observed and correlated with both personal benzene exposures and levels of urinary metabolites (S-phenylmercapuric acid and t,t-muconic acid) and albumin adducts of benzene oxide and 1,4-benzeoquinone. Conclusions The depressions in RBC, WBC, and neutrophils observed in this study are not only exposure dependent, but also significantly different in the lowest exposed group (at or below 0.25 ppm) compared with unexposed subjects. The results of the present study appear to suggest that lymphocytes may not be more sensitive to chronic benzene exposure than neutrophils.