The precautionary principle is a German export. It arose as the Vorsorgeprinzip in German environmental law in the early 1970s and was written into the Federal Emission Protection Act of 15 March 1974.
It reached international law in 1987 at the North Sea conference, and was entrenched in 1992 as Principle 15 of the Rio Declaration, from where it passed into most international environmental conventions.
The principle holds that where serious or irreversible harm is possible, the absence of full scientific certainty is not a reason to wait.
Germany did not adopt an international norm about prevention. It wrote one and the world took it.