Abstract: Objective To observe the T cell subsets and blood cells in the peripheral blood of workers exposed to low levels of benzene for one year,and to investigate the relationship between T cell function impairment and benzene-induced hematopoietic injury after benzene exposure.Methods Eighty-eight workers (58 males and 30 females,aged 18~22 years) who just began to work in the workshop of a paint factory with exposure to benzene in Guangzhou,China were assigned to experimental group,and 88 workers (58 males and 30 females,aged 18~25 years) who worked in the workshop without exposure to benzene were selected as controls.The blood samples of the workers were examined once every 4 months to measure the percentages of peripheral T cell subsets and peripheral blood cell counts in the one-year study.The benzene concentrations at operation points were also measured.Results The peripheral blood cell counts in the benzene-exposed workers had no significant changes in the first and second examinations; the white blood cell (WBC) counts in the experimental group in the third and fourth examinations were significantly lower than that in the control group [(6.4±3.0) ×109/L and (6.3±2.7)×109/L vs (7.3±3.0)×109/L,P<0.05],and the platelet (PLT) count in the experimental group in the fourth examination was also significantly lower than that in the control group [(179±74)×109/L vs (189±70)×109/L,P<0.05].Compared with those in the control group (CD4+:54.29±12.78%,CD8+:37.25±12.30%),the percentage of CD3 + T cells in the experimental group increased in the third examination; the percentage of CD4+ T cells in the experimental group decreased continuously in the second,third,and fourth examinations (50.77±11.05%,45.40±9.41%,and 41.27±10.62%),while the percentage of CD8+ T cells in the experimental group kept increasing (46.07±10.18%,50.36±10.62%,and 56.40±9.41%) (P<0.05).Conclusion The change in T cell subsets precedes that in the blood system in the workers exposed to low levels of benzene.