Education Department of Jilin Province, Key Laboratory of Environmental Materials and Pollution Control, School of Environmental Science and Engineering, Jilin Normal University, Siping, Jilin, 136000, People's Republic of China. [Email]
The internal critical concentration represented by the critical body residue (CBR) is an ideal indicator for reflecting the toxicity of a chemical. Although some authors have realized that the CBR50 can be calculated from the LC50 via the bioconcentration factor (BCF), the effects of exposure time and exposure concentration on the relationship between the LC50 and CBR50 have not been investigated to date. In this paper, the LC50 and CBR50 of ortho-dinitrobenzene in zebrafish were experimentally determined and their relationship was investigated. The results showed that ortho-dinitrobenzene exhibited excess toxicity and cannot completely be identified as a reactive compound based on toxic ratio. Comparison of the measured CBR50 and the CBR50 calculated from the LC50 via the BCF showed that there was a 0.46 log unit difference. Investigation of the relationship between the concentration in fish calculated by the toxicokinetic model and exposure time showed that the bio-uptake of fish was fast and reached a steady state in the toxicity test, indicating that the difference in CBR50 values could not be attributed to the different exposure times used in toxicity and BCF assays. On the other hand, investigation of the measured bioconcentration ratio (BCR) showed that the BCR (or BCFapp) decreased with increasing exposure concentration. Compared with the CBR50 calculated from the LC50 via the BCF, the CBR50 calculated from the LC50 via the BCFapp is close to the measured CBR50, suggesting that the difference in CBR50 values is attributed to the different exposure concentrations used in the BCF and toxicity assays.