Objectives Benzene is a well-known haematological toxin causing aplastic anaemia and leukaemia. Some recent studies have shown that low-level benzene exposure (<1 ppm) disturbs the haematopoietic system. However, other studies showed inconsistent results. The aim of the present study was to examine the relationship between low-level benzene exposure and blood cell counts in Korean workers.

Methods Blood cell counts of benzene-exposed workers were extracted from a nationwide Special Health Examination Database from 2000 to 2008. If a worker did not take a blood test for benzene between 2000 and 2004, the worker was selected for analysis. In total, 8679 personal air benzene measurements were extracted from the nationwide Workplace Environment Measurement Database from 2004 to 2008. Mean benzene levels were calculated and assigned to benzene-exposed workers using various combinations of factory/industry/process codes. Mixed-effects models were used to examine dose-related associations between benzene levels and white blood cell (WBC), red blood cell (RBC), platelet, neutrophil and lymphocyte counts.

Results In total, 21 140 blood samples were tested from 10 702 workers between 2005 and 2008; 40% of the workers had repeated blood tests (average, 3.4 times). RBC counts in male workers showed a significant negative association with low-level benzene exposure. WBC, platelet, neutrophil and lymphocyte counts did not show a consistent association with low-level benzene exposure.

Conclusions Our findings support the potential haematotoxicity of low-level benzene exposure (<1 ppm). A longitudinal study with direct benzene measurements for exposed workers is needed to confirm the toxicity of low-level benzene exposure.