Studies On The Joint-toxicity Of Gasous Benzene And Formaldehyde To Mice

In recent years, indoor air pollution caused by decoration has been widely noticed. From the investigation of indoor air pollution, formaldehyde (FA) and benzene (BZ) are the two most important indoor air pollutants of decoration for their high level concentration and severe biological toxicity. According to the epidemiological survey, the two topical compounds may cause some serious sickness such as asthma and leukemia. However, the mechanisms of multi-pathogenic associated with them are not well known. This paper tries to explore the effect of benzene on the development of leukaemia in mice through establishing the model of acute lymphoblastic leukemia (All) mice. Fothermore, in order to establish suitable method to evaluate the toxiceffects of the two compounds at low-level expose, some techniques as single cell gel electrophoresis(SCGE), micronucleus test(MNT), flow cytometer were applied to research genetic toxicity, immune toxicity and oxidation damage in mice caused by inhalation the mixtures of BZ and FA. The experimental evidences are provided for selecting the early biological signs of indoor FA and BZ indecators for people who exposed. The evidence is also provided for understanding the mechanism of joint-exposure, the prevention of leukemia.The results are as follows:(1) acute lymphocyte leukaemia mice model shows that low-dose exposure of BZ can lead to obvious DNA damage to 615 mice. This means that long effect of indoor BZ exposure might be a primary reason of infant leukemia which should be paid more attention. The DNA damage of marrow cell in the group of BZ compared with tumor vaccinated group and BZ exposing group is mitigated. Whether it is because of the hormesis of lowl dose needs to be further confirmed. Just as tretinoin can be used to treat leukemia, whether low dose of benzene can be used to control the development of leukemia remain to be further studied.(2) Sub-acute experimental model of inhalation mixed gaseous BZ and FA . The results showed that inhalation of FA could decrease the body weight of mice. The inhalation of BZ can not cause the decrease of body weight of mice in acute exposure period. Both BZ and FA can affect the modulus of mouse's liver, spleen and thymus, and the two compounds have the joint effects. Liver is the most sensitive organ to this kind of stimulus. In the acute exposure period, BZ and FA can't increase the DNA damage of lymphocyte of peripheral blood and marrow cell.(3)The results of the sub-chronic and chronic animal experiments showed that both BZ and FA could cause the decrease of mice body weight. FA can decrease the body weight of mice persistently but for BZ, this effects was end at 60 days. BZ and FA can cause the DNA damage of BALB/c mice, and the two compounds also had the additional effects. Simultaneously, the damage form of DNA were differrent: the main form of DNA damage caused by FA was DNA-protrosslinks (DPC) , and BZ exposure led the DNA strands breakage. PMT results showed that both BZ and FA could increase micronucleus of peripheral blood and marrow cell in mice. The kind of toxic effect of benzene is more serious than that of FA. They also have the joint effects. Under the conditions of this experment, the apoptosis of marrow cell can be occured, and the apoptosis rate has remarkably increased when inhalation of BZ mixed gases of FA: from the percentage change of different period of marrow cell cycle, BZ can block cells in their mitotic phase and block the development of the cells cycle, FA can stop cells in the G1/G0 period. Inhalation of BZ and FA can reduce the modulus of MICE liver, spleen and thymus, this shows the liver's function of detoxication has brokendown, and the immune function is restrained. At the same time, modulus of lung increases. The experiment of the oxidations of lung tissuealso shows that the content of MDA in mice lung increased remarkably, and SOD was decreased, so the oxidation damage of lung was severe. BZ and FA have the additional effects. The oxidation damage of plasm is also obvious, BZ and FA have also expressed the joint function. The contants of LDH in spleen and thymus in each group has been changed. During the subchronic period, the LDH level of mice in every group has increased. BZ and FA have the additional effects. During the chronic period, the contants of LDH in thymus of FA exposure group decreased; and it in benzene group increased. BZ and FA also have the additional effects. That shows the changes of LDH contants is different by exposing the different toxicants. During the chronic period, the plasm LDH in each group of mice increased and BZ and FA have the additional effects. Inhalation of BZ and FA can cause the reduction of peripheral blood white blood cells and lymphocytes and cause the oxidation damage of liver and plasma in mice. The pathology result shows that BZ and FA can cause the inflammatory pathological changes of liver, lung, spleen and thymus and restrain the immune function of spleen and thymus.From above results, mixed exposure of BZ and FA will not cause genetic damage during the acute period. However, during the chronic period, the toxic effects of them has expressed the characteristics of multiple organs toxicity, multiple toxic mechanisms and multiple genotoxicity. They have the additional effects on DNA damage and oxidation damage and immune restrain.