## 1 Introduction  
The emerging problem of the pollution of river environments by pharmaceuticals and personal care products (PPCPs) has received a large amount of attention [1; 2; 3]. Pharmaceuticals are designed to have specific physiological effects on target areas of the body. Concern is therefore rising about their toxic effects on ecosystems when discharged into environmental water, even when they are present at low concentrations. Furthermore, their impacts on human health via residues contaminating drinking water should be taken into consideration [4; 5; 6; 7]. Generally, the concentrations of these compounds are low (roughly in the range from ng/L to ug/L) worldwide [7; 8; 9]. Even in this low concentration range, however, there have been reports of the endocrine-disrupting chemicals that have serious environmental impacts, such as the feminization of male fishes [10; 11]. PPCPs include different groups of compounds typified by their chemical characteristics, structure, mechanism of action, mode of action, and their therapeutic use to treat specific diseases. Particularly,anticancer drugs are emerging as an area of growing interest because of their promotion of a long lifespan via the suppression of human death through their use as a chemotherapy [12; 13]. Human life is changing in response to recent developments in science and technology. In Japan, cancer has been the country's top cause of death since 1981, accounting for 29% of all deaths in 2015. This was nearly double the rate of the second-highest cause of death, heart disease (15%) [14]. In addition, because of the aging of the Japanese population [14], the number of cancer patients who need treatment is likely to increase in future. Increasing numbers of new pharmaceuticals for chemotherapy [15], which, along with surgery and radiotherapy, is an important treatment for cancer, have been developed in recent years [16]. The use of anticancer agents in clinical situations is also increasing, whereas the rates of adoption of surgical therapy and chemotherapy in Japan have stayed about the same [17]. According to their mechanisms of action, anticancer drugs are mainly classified into alkylating agents, antimetabolites, hormone antagonists, cytotoxic antibiotics, antimiotics, cytotoxic quinolones, and topoisomerase inhibitors. Because all of these anticancer drugs have physiological activity and are highly cytostatic, there are many concerns about their cytostatic effects on aquatic ecosystems and on organisms living in the aquatic environments [12; 18; 19; 20]. In fact, an anticancer drug, tamoxifen (TAM), inhibited the reproduction and growth of _Daplinia_ at 120 ng/L [21] and showed a predicted no-effect concentration of 81 ng/L for fish, plankton, and algae [22]. In addition, anticancer drugs are present in the sediments in river environments. Therefore, serious pollution problems sometimes arise from contaminated river water because of the exposure of benthic organisms and bioaccumulation in predators such as fish along the ecological chain through predation [23; 24]. The sedimented substances affect not only river environments, but also marine environments, and humans are at risk when they eat fish polluted with them through bioaccumulation [25; 26; 27]. At present, the pollution aspect of anticancer drugs in Japan has been analyzed only in the very limited area surrounding the Yodo River since 2009 [13; 28; 29; 30; 31]. Their occurrence in the river water and sediments, including from hospital and sewage treatment effluents [13; 28; 32], their fate after discharge [31], and their attenuation properties [29; 30], were reported in a separate fashion. The time has come to make an overview of the status of anticancer drugs in the environmental water of the Yodo River basin.