| Objective: With the rising of the indoor decoration, a lot of inferior building materials including pollutants emerge in the house. As a result, the indoor air was polluted more and more seriously.Because a lot of formaldehyde and benzenes are used in tectonic stuffs, formaldehyde and toluene become the main pollutants of indoor air. Both of them have serious biological toxicity, high concentration in house, which may have combined toxic effect on human body. Currently there are much researchs about the single toxicity of formaldehyde and toluene, while few on the joint toxicity of them, let alone the joint genotoxicity and the mechanism. This study focuses on exploring the genotoxicity and their mechanism in mice inhaling formaldehyde and toluene, and providing the theoretical reference for health effects caused by indoor air pollution. Methods: Seventy-two healthy and clean KM mice were randomly divided into nine groups, according to the method of 3×3 factorial design. The control groups were exposed at clean air, the formaldehyde treatment groups were exposed at dosage of 1mg/m~3, 5mg/m~3, the toluene exposuring groups were exposed at dosage of 400mg/m~3, 2000mg/m~3 and the combined treatment groups of formaldehyde and toluene were exposed at dosage of(1+400)mg/m~3, (1+2000)mg/m~3,(5+400)mg/m~3,(5+2000)mg/m~3 respectively. The mice were exposed to formaldehyde and toluene two hours per day for 14 days consecutively. During the experiment, there are no water or food for the mice, other times freely drinking and eating. Then the mice were killed by infusing normal saline to the heart, to ensure that there was no blood in the body of mice, and then took out the marrow, liver and lung quickly. At the end, observe the damage of marrow cells, determine the activity of superoxide dismutase (SOD), the contents of maleic dialdehyde (MDA) and glutathione (GSH) and the coefficient of DNA-protein crosslink (DPC) in livers and lungs of the mice.Results:1. The toxicity of formaldehyde and toluene on bone-marrow cells of mice:(1) Micronucleus rate of bone-marrow cells of mice in joint exposure groups were much higher than the control group (P<0.05), and the two substances could induce micronucleus. There was interaction in micronucleus rate between formaldehyde and toluene (P<0.05), which showed synergistic effect. (2) When the mice were exposed to formaldehyde and toluene, DNA damage on bone narrow cells of mice could be detected. The percentage of tail DNA and tail moment of bone-marrow cells of mice in exposured groups were higher than the control group (P<0.05). The two substances existed interaction in percentage of tail DNA and tail moment (P<0.05), and they have synergistic effect. 2. Joint genotoxic effect of liver of mice inhaling formaldehyde and toluene: (1) Compared with the control group, the activity of superoxide dismutase (SOD) and the contents of glutathione (GSH) of liver in formaldehyde or toluene exposure groups were much lower, and the contents of maleic dialdehyde (MDA) were much higher (P<0.05). They can cause the contents of glutathione (GSH) and the activity of superoxide dismutase (SOD) decreased, and the contents of maleic dialdehyde (MDA) increased. There was interaction in oxidative damage of livers of mice (P<0.05), which expressed synergistic toxic effect on maleic dialdehyde (MDA). (2) The coefficient of DNA-protein crosslink (DPC) of liver of mice were much higher than the control groups (P<0.05). There was significant interaction in the coefficient of DPC of liver of mice (P<0.05), and they displayed synergistic effect.3. Joint genotoxic effect of lungs of mice inhaling formaldehyde and toluene: (1) The contents of maleic dialdehyde (MDA) were much higher than the control groups. The activity of superoxide dismutase (SOD) and the contents of glutathione (GSH) of lung in exposed groups were much lower (P<0.05). There were interaction between formaldehyde and toluene in the contents of glutathione (GSH) and maleic dialdehyde (MDA) of lungs (P<0.05), but there was no interaction in the activity of superoxide dismutase (SOD) (P>0.05). They had a significant synergistic toxic effect on maleic dialdehyde (MDA) and glutathione (GSH). (2) Formaldehyde and toluene can lead to the coefficient of DNA-protein crosslink (DPC) increased. There was interaction in the coefficient of DPC of lung of mice between formaldehyde and toluene (P<0.05). The joint effect showed synergistic effect.Conclusion: Formaldehyde and toluene had genotoxicity in mice of single or joint exposure. They can lead to DNA damage of bone-marrow cells, induce lipid peroxidation damage and DPC of liver and lung tissue. Joint exposure of formaldehyde and toluene can induce DNA breakage at low exposed dose, and they can result DPC at relatively high concentration. The two substances may have synergistic effect on genotoxicity of mice. The lipid peroxidation damage and DNA damage might be the important mechanisms of genetic damage of mice caused by formaldehyde and toluene. |
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