## 3 Results and Discussion
### Allocation of Anticancer Drugs in the Sediment and Suspended Solid Samples
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Compound** & **Sample** & \multicolumn{4}{c}{**Concentration (ng/L)**} & \multicolumn{2}{c}{**Frequency**} \\ \cline{3-6}  & **Type** & **Mean (SD)** & **Median** & **Max** & **Min** & **(\%)** \\ \hline \multirow{2}{*}{\begin{tabular}{c} Bicalutamide \\ (BLT) \\ \end{tabular} } & Main stream & 55 (71) & 32 & 254 & N.D. & 83 \\  & Tributary & 46 (43) & 30 & 151 & N.D. & 94 \\  & STP effluent & 316 (303) & 245 & 1032 & 49 & 100 \\  & STP effluent (ozonation) & 13 (20) & 5 & 41 & N.D. & 50 \\  & Main stream & 5 (16) & N.D. & 76 & N.D. & 33 \\  & Tributary & 8 (12) & N.D. & 33 & N.D. & 44 \\  & STP effluent & 1 (3) & N.D. & 9 & N.D. & 10 \\  & STP effluent (ozonation) & N.D. (0) & N.D. & N.D. & N.D. & 0 \\ \hline \multirow{3}{*}{\
\begin{tabular}{c} Cyclophosphamide \\ (CP) \\ \end{tabular} } & Main stream & 3 (5) & 2 & 16 & N.D. & 63 \\  & Tributary & 4 (6) & 3 & 20 & N.D. & 56 \\  & STP effluent & 11 (7) & 10 & 20 & N.D. & 90 \\  & STP effluent (ozonation) & 7 (10) & 3 & 22 & N.D. & 50 \\ \hline \multirow{3}{*}{
\begin{tabular}{c} Capecitabine \\ (CAP) \\ \end{tabular} } & STP effluent & 3 (4) & 2 & 20 & N.D. & 88 \\  & Tributary & 3 (4) & 1 & 16 & N.D. & 100 \\  & STP effluent & 6 (3) & 6 & 11 & 2 & 100 \\  & STP effluent (ozonation) & 2 (2) & 2 & 4 & N.D. & 50 \\  & Main stream & 2 (8) & N.D. & 39 & N.D. & 8 \\  & Tributary & 1 (3) & N.D. & 12 & N.D. & 6 \\  & STP effluent & 1 (3) & N.D. & 8 & N.D. & 20 \\  & STP effluent (ozonation) & N.D. (0) & N.D. & N.D. & N.D. & 0 \\ Tegafur & Main stream & 5 (13) & N.D. & 56 & N.D. & 25 \\  & Tributary & 6 (12) & N.D. & 35 & N.D. & 25 \\  & STP effluent & 20 (16) & 23 & 49 & N.D. & 70 \\  & STP effluent (ozonation) & 4 (8) & N.D. & 17 & N.D. & 25 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Detection of the target anticancer drugs in river waters and STP effluents (n = 24 (main stream), n = 16 (trubutary), n = 10 (STP effluent), n = 10 (STP effluent—ozonation)) (reproduced from [30]). These observations suggest that the anticancer drugs present in the river water environment were mainly distributed in the liquid phase. The major reason of this biased view could be ascribed to the difference in their octanol-water partition coefficients, log\(K_{\text{OW}}\) (log\(P\)) values [68], which ranged from \(-0.7\) to \(5.1\) (Table 1). However, the overall results suggest that not only the log\(P\) values but also the electric charge and its density (associated with the functional groups in the anticancer drugs) participate as factors which determine the degree of adsorption onto the particles [37, 69]. When the log\(K_{\text{d}}\) values were estimated for the anticancer drugs in the solid state samples, positive values were detected only in the case of BLT; 4.3 for the suspended solids at the Hirakata Bridge, while 0.8 for the river sediments at the Suita Bridge. The value at the Suita Bridge was similar to that obtained by the laboratory experiment for the river sediments at this bridge, suggesting the possibility that the capacity for sorption onto the river sediments could be predicted by estimation. However, the log\(K_{\text{d}}\) values for the other anticancer drugs whose concentrations were below LOD remained undetermined. This lack of log\(K_{\text{d}}\) values or abundance of concentrations below LOD was the consequence of attenuation due to photodegradation by sunlight and biodegradation through water flow over time [28, 70]. The higher positive value for the suspended solids compared to the sediments was in association with the relatively low abundance of the suspended solids.