2017 Volume 20 Issue 1 Pages 21-33
We examined the acute-to-chronic toxicity ratio (ACR) with use in the risk assessment of aquatic combined toxicity. The deterministic method using fixed values and the probabilistic method using distributions are applied to ACR. 1000 sets of virtual mixture each consisting of 2, 5, 10 or 20 components were created. And simulation was conducted to derive the predicted no effect concentration of mixture (PNECmix) of those mixtures. First, PNECmixs derived using fixed ACR and true PNECmixs derived from NOEC without using ACR were compared. It was shown that the PNECmixs derived using the fixed ACR became smaller than the true PNECmixs when the number of chemicals in the mixture increased. Next, PNECmixs derived using probability distribution of ACR and true PNECmixs were compared. It was shown that the differences between the PNECmixs derived using the probability distribution of ACR and the true PNECmixs got smaller when the number of chemicals in the mixture increased. As a result, it was suggested that in the risk assessment of complex toxicity, fixed ACR derives conservatively biased PNECmixs and probabilistic ACR derives realistic PNECmixs.
