Objective To study the neurotoxicity of joint exposure to formaldehyde and benzene in mice, so as to provide scientific basis for the synthetic evaluation of the toxicity of formaldehyde and benzene.
Methods Sixty KM mice were randomly divided into 10 groups. The formaldehyde treatment groups were exposed at dosage of 1 mg/m3, 3 mg/m3, 5 mg/m3; the benzene treatment groups were exposed at dosage of 500 mg/m3, 1 500 mg/m3, 2 500 mg/m3; and the combined formaldehyde and benzene treatment groups were exposed at dosage of 0.5 mg/m3+250 mg/m3, 1.5 mg/m3+750 mg/m3, 2.5 mg/m3+1 250 mg/m3 respectively. The mice were exposed to formaldehyde and benzene by static state inhalation in a chamber for 14 days, 2 hours a day. Then their behavior of learning and memory were tested by Morris water maze experiment and oxidative damage was detected in the cerebral tissue.
Results Morris water maze test in space training and learning indicated that escape latency significantly extended in the high dose of formaldehyde treatment group, the moderate and high dose of benzene treatment groups and all the combined treatment groups(P<0.05). Compared with single exposure groups, escape latency significantly extended in the moderate and high dose of combined treatment groups (P<0.05). In space exploration experiments, the proportion of time of the target quadrant in the moderate and high dose of formaldehyde treatment groups, the high dose of benzene treatment group, and all the combined treatment groups were less than the negative control groups (P<0.05). The proportion of time of the target quadrant in the every dose of combined treatment groups were significantly decreased compared with single exposure (P<0.05). The activities of SOD in the moderate and high-dose formaldehyde and benzene treatment groups and all the joint exposure groups were decreased, while the contents of MDA increased in the high dose of benzene treatment group, all the formaldehyde's and joint exposure groups increased. Compared with formaldehyde or benzene exposure groups, the activities of SOD in joint exposure groups were significantly decreased (P<0.05)and contents of MDA were obviously increased (P<0.05).
Conclusion Formaldehyde and benzene have obvious toxic effects on central nervous system in mice. The neurotoxicity of formaldehyde and benzene combined exposure in mice is more severe than their single exposure, which may be caused by synergistic toxic effect.
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