In order to compile as much available monitoring data as possible for these metals in rivers across Japan, we reviewed the Comprehensive Information Website for Water Environment and the Water Information System as well as existing literature covering over 1000 sampling sites in total (excluding the two databases). The literature included peer reviewed papers (e.g., and Japanese project reports. Based on examination of whether the measured concentrations (preferably, dissolved concentrations) of all six metals were relatively low, we selected three datasets: the largescale measurement data of ; measurements from metal-contaminated rivers affected by legacy mines as well as nearby reference rivers ; and measurements from rivers to assess the ecological impacts of Ni . All these studies reported dissolved metal concentrations by filtering water samples through filters with a pore size of 0.45 μm and analyzing them using inductively coupled plasma mass spectrometers (ICP-MS) or inductively coupled plasma optical emission spectrometers (ICP-OES). We analyzed data from a total of 531 sampling sites (excluding 7 estuarine sites from ; see Figure ). All the complied data are available in the Supporting information (Table ).