The objectives of this study were thus threefold: (1) to compile available measurement data of metals relevant to ecological risk assessment in rivers across Japan, (2) to identify metals of particular concern based on their relative ecological risks, and (3) to elucidate the realistic exposure profiles of these metals based on the compiled data. The outcomes of this study were expected to provide valuable insights into realistic concentration levels and ratios, which are critical for assessing the ecological risks and effects of exposure to mixtures of metals in Japanese rivers.