The ecological hazard and risk assessment of individual chemicals in Japan have been far behind the other developed countries such as the US and European countries and have long been limited to fish acute toxicity assessment for pesticides. After the recommendation by Organization for Economic Cooperation and Development (OECD) in 2002, ecological hazard and risk assessment for industrial chemicals was implemented in Chemical Substances Control Law (CSCL) and that for pesticides was expanded to crustaceans and algae in 2003 by Ministry of the Environment. Environmental standard for water quality to protect aquatic organisms was also first implemented in 2003 for zinc while the guidance for the ecological risk assessment for human pharmaceuticals was implemented at last in 2016 by Ministry of Health, Labor, and Welfare. Due to the increasing number of chemicals manufactured, used, and wasted, the ecological hazard and risk assessment for complex mixtures have become concern and investigated but the component-based approach in the ecological risk assessment has not yet well established and is far behind that in human health risk assessment. Alternatively, whole mixture approach such as the direct bioassay of effluent and ambient water has been implemented in some developed countries but the attempt to implement the Japanese version of Whole Effluent Toxicity system was ended up with the voluntary-based measure. Therefore, component-based approach for the grouping of chemicals based on chemical structure, use and mode of action should be started by the development of guidance documents possibly used in CSCL and other regulations with utilizing new approach methods (NAMs) in addition to conventional ecological testing combined with proper whole mixture approach for monitoring effluent and ambient water to cover such growing numbers of diverse small production volume chemicals.