Neurotoxicity Of Joint Exposure To Formaldehyde And Benzene In Mice

Objective:In recent years, with the development of society and the continuous improvement of people's living standards, indoor decorating becomes the trend of fashion, finally the condition of indoor air pollution becomes increasingly serious. Formaldehyde and benzene released by ornament materials have become the main pollutants of indoor air. Formaldehyde and benzene usually exist together indoors in high concentrations, so they can have combined toxic effect on human body. Now there are lots of reports about neurotoxic effect induced by formaldehyde or benzene, but few about neurotoxicity of joint exposure to the two substances. This study is to explore the neurotoxicity of joint exposure to formaldehyde and benzene in mice, to provide scientific basis for the synthetic evaluation of the security of formaldehyde and benzene, and provide theory references for the researches on indoor pollution.Methods:Sixty KM mice were randomly divided into 10 groups. The formaldehyde treatment groups were exposed at dosage of 1 mg/m3,3 mg/m3,5mg/m3, the benzene treatment groups were exposed at dosage of 500 mg/m3,1500 mg/m3,2500 mg/m3 and the formaldehyde and benzene combined 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+1250 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 step-down test and Morris water maze experiment, and oxidative damage were detected in the cerebral tissue. 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. At the end, the activities of SOD,the contents of MDA in brains could be determined and DNA damages in brain cells could be observed.Results:1,Formaldehyde and benzene could degrade the learning and memory abilities of mice. (1)Step-down test showed that, the incubation period reduced and number of mistakes increased in the moderate and high dose of formaldehyde treatment group,the moderate and high dose of benzene treatment groups and all the combined treatment groups(P<0.05); the incubation period significantly reduced in the moderate and high dose of combined treatment groups(P<0.05) compared with single exposure.(2)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 the 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 group,the high dose of benzene treatment groups 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).2,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 groups,all the formaldehyde's and joint exposure groups. 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).3,Formaldehyde and benzene could cause DNA damage in brain cells of mice:Compared with the negative control groups, the tail DNA% and Tail moment were increased in the low and moderate dose of formaldehyde and benzene treatment group(P<0.05).Meanwhile, the content of DPC was increased in the moderate and high dose of formaldehyde and benzene treatment groups(P<0.05). In all the combined treatment groups, the tail DNA%,Tail moment and the content of DPC were significantly increased compared with the negative control groups and single exposure groups(P<0.05).Conclusion:Formaldehyde and benzene had neurotoxicity in mice, it could degrade the learning and memory abilities of mice, result in lipid peroxide in brains and the DNA damage in brain cells of mice. It showed that DNA strand breakage was caused at low levels while DPC was induced at relatively higher levels. Maybe the joint neurotoxicity effect is synergistic. Lipid peroxide and DNA damage might be the important mechanisms of central nervous system function damage in mice induced by formaldehyde and benzene.