Investigation of Critical Body Residues and Modes of Toxic Action Based on Injection and Aquatic Exposure in Fish.

The internal concentration represented by the critical body residue (CBR) is an ideal indicator to reflect the intrinsic toxicity of a chemical. Whilst some studies have been performed on CBR, the effect of exposure route on internal toxicity has not been investigated for fish. In this paper, acute toxicity data to fish comprising LC and LD values were used to investigate CBR. The results showed that exposure route can significantly affect the internal concentration. LD and CBR calculated from LC and BCF both vary independently of hydrophobicity as expressed by log K; conversely, LC is related to log K. A poor relationship was observed between LC and LD, but the relationship can be improved significantly by introduction of log K because log CBR is positively related to log LD. The parallel relationship of log CBR-log K and log LD-log K indicates that LD does not reflect the actual internal concentration. The average LD is close to the average CBR for less inert and reactive compounds, but greater than the average CBR for baseline compounds. This difference is due to the lipid fraction being the major storage site for most of the baseline compounds. Investigation on the calculated and observed CBRs shows that calculated CBRs are close to observed CBRs for most of compounds. However, systemic deviations of calculated CBRs have been observed for some compounds. The reasons for these systemic deviations may be attributed to BCF, equilibrium time and experimental error of LC. These factors are important and should be considered in the calculation of CBRs. [ABSTRACT FROM AUTHOR]