The standard definition, according to the Rio Declaration on Environment and Development (1992), is: “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.” If some action or practice or policy has a risk of harming people or the environment, and there is some uncertainty about the nature or scope of that risk, corrective action should nevertheless be taken in order to protect people and the environment. In effect, the action should be stopped, the practice discontinued, or the policy changed to avoid the risk.


 The principle shifts the burden to those who propound an action or product to prove no harm once it is determined that there is a plausible risk to the pubic or environment as a result of that action or product.  Generally, the principle may only be invoked when the three preliminary conditions are met: identification of potentially adverse effects; evaluation of the scientific data available; the extent of scientific uncertainty.

The European Union has officially adopted the principle. The Treaty on The Functioning of the European Union (TFEU), in Article 191(2), requires that EU policy on the environment “… shall be based on the precautionary principle and on the principles that preventive action should be taken, that environmental damage should as a priority be rectified at source and that the polluter should pay.”


Some further ideas to explore on Precautionary Principle

Examine the recent action by the EU to ban certain pesticides because of the risk to bees and determine to what extent the precautionary principle was applied.

Which of the three conditions for applying the precautionary principle have been satisfied for applying the principle to climate change.

Are the Northern Ireland and Irish governments required to apply the precautionary principle to their decisions on whether to permit fracking on the island of Ireland?



“The precautionary principle,” Europa Summaries of EU legislation

Prof. N. de Sadeleer, “The Precautionary Principle in EU Law,” AV&S, 2010, 173-184.

The Treaty on The Functioning of the European Union (TFEU),



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