2nd edition. The purpose of the WHO human health risk assessment toolkit: chemical hazards is to provide its users with guidance to identify, acquire and use the information needed to assess chemical hazards, exposures and the corresponding health risks in their given health risk assessment contexts at local and/or national levels. The Toolkit provides road maps for conducting a human health risk assessment, identifies information that must be gathered to complete an assessment and provides electronic links to international resources from which the user can obtain information and methods essential for conducting the human health risk assessment