The precautionary principle, or precautionary approach, is one of the foundational principles of environmental law.  As articulated in Principle 15 of the Rio Declaration on Environment and Development (1992), it states: "Where there are threats of serious or irreversible damage, lack of full scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation."  It has been incorporated into numerous international instruments, such as the Convention on Biological Diversity and the United Nations Framework Convention on Change, as well as regional, national and subnational law.

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