Precautionary Principle

A public‑health and policy rule that, when an activity raises plausible risk of serious or irreversible harm and scientific certainty is lacking, the absence of full proof should not be used to postpone proportionate preventive measures; those measures should be commensurate with the severity and plausibility of the potential harm and the available means to reduce it.

A policy rule used primarily in environmental and public-health contexts that permits or requires preventive measures when an activity poses a plausible risk of serious or irreversible harm, even if full scientific certainty about causation or magnitude is lacking; measures must be reasonable, proportionate and non-arbitrary.