Toxicity Effects Of Chlorobenzenes And Benzidines On Zebrafish Embryos

Chloro-benzenes have the intense carcinogenesis, tetratogenesis and mutagenesis, and may enter human body through food chain and are concentrated at there, thus endanger the human health. Similarly, benzidines are suspected to be carcinogenic to human beings. Furthermore, these two kinds organic compounds have the characteristics of persisting existence, widespread distribution, biological accumulation and poisonous. In addition, they were used to industry in large-scale and for a long time, thus we must take them threat seriously to the natural environment and human health, and pay a worldwide concern.The chloro-benzenes studied in our paper included chlorobenzene, o-dichlorobenzene, m-dichlorobenzene, p-dichlorobenzene, 1,2,4-trichlorobenzene. Those benzidines included benzidine, 3,3'-dimethoxy benzidine, 3,3'-dimethylbenzidine and 3,3'-dichlorobenzidine. The zebrafish embryos were used to test their individual and combinational acute toxicities, including lethal effects and sublethal effect, and the dose-effect relationships between the various toxicological endpoints and pollutant exposure concentrations as well. Meanwhile, their poisonous mechanisms were also discussed initially. The main points as follows:(1) After exposuring to the chloro-benzenes and benzidines for certain periods, two toxicological phenomenons were emerged during the zebrafish embryonic development, one was kind I-lethal effects, and the other was kind II-sublethal effects. The toxicological endpoints of kind I included egg condensation, gastrula non-development, non-somite, tail non-extension, non-heartbeat and non-hatching etc. Those of kind II included the remarkable reduction of somites, non-blood circulation, eyespot non-development, non-active movement after 24hr, remarkable reduction of heart rate, melanocyte cells non-development, various abnormalities and hatch-delay etc.(2) The results attained from individual acute toxicity experiments showed that the embryotoxicities of chloro-benzenes increased in the following turn: 1,2,4-trichlorobenzenes>p-dichlorobenzene>m-dichlorobenzene>o-dichlorodebenzene>chlorobe nzene. They were correlated with molecular weight size, number and position of substituting groups. Those of benzidines increased in the following turn: 3,3'-dichlorobenzidine> 3,3'-dimethylbenzidine> 3,3'-dimethoxylbenzidine> benzidine. (3) In combinative acute toxicity experiments, we took 48h egg condensation EC50 as standard and took the chlorobenzene and the benzidine as basic. The experiments proved that chloro-benzenes mainly had antagonism actions, but benzidines mainly had additive actions.(4) Chloro-benzenes are inert compound, narcotize non-polar to zebrafish embryo, and are basic toxicity. The toxicity is not only related with compound in two interaction assignments, but also with the compound in the organism, moreover, it is also affectedly electronic factor of compounds or the three-dimensional effect.(5) On the other hand, benzidines are sub-inert compounds, polar narcotism and thus are higher toxicity than basic ones. Which send the poisonous process to the aquatic organism, first experience compound in the two (aqueous phase and biofacies) allocation processes. The more compounds enter the biofacies, the more opportunities will created for. As a result the polar stupefactive toxicity will become high.