Objective To explore genotoxicity of formaldehyde and benzene joint inhalation on bone-marrow cells of male mice, and to provide a scientific basis about evaluating the safety exposure to formaldehyde and benzene.
Methods Sixty healthy and clean Kunming inbred strain male mice were randomly divided into 10 groups with 6 mice in each group. The negative control group were exposed to clean air. The 3 formaldehyde treatment groups were exposed to formaldehyde at dosage of 1.0 mg/m3 (the low dose group), 3.0 mg/m3 (the moderate dose group), or 5.0 mg/m3 (the high dose group). The benzene treatment groups were exposed to benzene at dosage of 500.0 mg/m3 (the low dose group), 1 500.0 mg/m3 (the moderate dose group), or 2 500.0 mg/m3 (the high dose group). The joint treatment groups of formaldehyde and benzene were exposed to those at dosage of 0.5+250.0 mg/m3 (formaldehyde+benzene), 1.5+750.0 mg/m3, and 2.5+1 250.0 mg/m3 respectively. The treatments were conducted by static inhaling for two consecutive weeks, two hours a day, then the mice were killed on 15th day. The genotoxicity of formaldehyde and benzene was tested by micronucleus assay and single cell gel electrophoresis (comet assay).
Results Compared with the negative control group, micronucleus rate, tail DNA% and tail moment in each dose group of formaldehyde or benzene exposure groups and joint exposure groups were much higher (P < 0.05). Compared with single exposure groups, the micronucleus rate of each dose group of the joint exposure groups was much higher (P < 0.05), the tail DNA% and tail moment in the low dose group and the moderate dose group of the joint exposure groups were much higher (P < 0.05). The tail DNA% and tail moment in the high dose group of the joint exposure groups were much higher than single formaldehyde high dose group (P < 0.05), but not higher than single benzene high dose group.
Conclusion The genetoxic effect of combined exposure to formaldehyde and benzene on the bone-marrow cells of the male mice was more severe than that of the single exposure, which may be caused by the synergistic toxic effect.
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