The Principle of Precaution is a proactive approach to risk management that aims to prevent harm before it occurs, rather than waiting for scientific evidence to confirm the existence of a risk.

The Principle of Precaution is most commonly applied when there is scientific uncertainty about the existence or extent of a risk, because it is better to take precautionary measures to prevent harm than to wait for scientific evidence to confirm the existence of a risk.

The Principle of Precaution has been used to justify a wide range of precautionary measures, including banning the use of certain chemicals in consumer products, requiring companies to conduct environmental impact assessments before starting new projects, and setting limits on the amount of pollution that can be released into the environment.

The Principle of Precaution has been criticized for being too vague and subjective, for leading to unnecessary restrictions on economic activity, and for being used to justify protectionist policies.

The Principle of Precaution can be applied in a way that is both effective and proportionate by using a risk-benefit analysis to weigh the potential harm against the costs of taking precautionary measures, by considering the scientific evidence and the level of uncertainty about the risk, and by involving stakeholders in the decision-making process.