2023 Volume 33 Issue Special_Issue Pages s19-s25
Combined exposure to multiple chemicals is one of the primary concerns related to risk assessment. In this study, the feasibility of using environmental fate models in exposure assessment of combined exposure was discussed. Specifically, spatio-temporal changes in the concentrations of three paddy herbicides (halosulfuron methyl, pyrazosulfuron ethyl, and cyclosulfamuron) were predicted for whole Japanese rivers, and the ecological risk assessment of combined exposure was estimated based on the predicted concentrations. The hazard index (HI), which is the sum of hazard quotients of the three herbicides, was calculated for the rivers. Temporal trends of the HI were demonstrated for six river mouths. The contribution of each herbicide when HI reached its maximum was also shown for the six rivers. Pyrazosulfuron ethyl made the largest contribution in the range of 0.62 to 0.95. The environmental fate model has potential to use for prioritizing target chemicals in exposure assessment and setting conditions for ecotoxicity tests.
