Objective To study the mechanisms of toxicity of chlorobenzenes on aquatic organisms so as to provide a scientific basis on selection of toxicological doses and toxicological endpoints for further experimental study.
Methods The chlorobenzenes studied in our experiment included chlorobenzene, o-dichlorobenzene, m-dichlorobenzene, p-dichlorobenzene, and 1,2,4-trichlorobenzene. The zebrafish embryos were used to test their individual acute toxicities. In this experiment we used 24 wells cell culture plate as the embryonic exposure experiment container. The exposed embryos were observed under microscope every 4 h, chlorinated benzene compounds on zebrafish embryos, including lethal effects and sublethal effects were recorded, and the changes in the corresponding toxicological endpoints were described, until the end of 72 h.
Results The EC50 values of all toxicological endpoints of chlorinated benzene compounds were measured experimentally, for example, 4 h embryonic development of the termination of EC50 values(mg/L) were:24.72 for 2,4-trichlorobenzenes, 76.47 for p-dichlorobenzene, 77.35 for m-dichlorobenzene, 86.31 for o-dichlorodebenzene, 89.43 for chlorobenzene and so on. The results showed that the embryotoxicities of chlorobenzenes decreased in the order as:1,2,4-trichlorobenzenes > p-dichlorobenzene > m-dichlorobenzene > o-dichlorodebenzene > chlorobenzene.
Conclusion The toxicity of chlorobenzenes on zebrafish was correlated with their molecular weight, number and position of substituting groups. The greater of molecular weight and the number of substituents, the severer of their toxicity.
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