Agenda 21 recommends that governments should intensify research and development on cost-effective alternatives for processes and substances currently resulting in the generation of hazardous wastes which pose particular problems for environmentally sound disposal or treatment. The possibility of ultimate phase-out of those substances that present an unreasonable or otherwise unmanageable risk or that are toxic, persistent and bioaccumulative should be considered as soon as practicable. Emphasis should be given to alternatives that could be economically accessible to developing countries.