PrintThe Precautionary Principle was initially proposed in the Declaration on Environment and Development at the United Nations Conference in Rio de Janeiro in 1992 and states that,
"In order to protect the environment, the precautionary approach shall be widely applied by States according to their capabilities. 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."
In other words, when considering actions (or inactions) whose consequence could pose serious or irreversible damage to human health or the environment, the burden of proof that those actions won't cause harm lies with those taking the action. The Precautionary Principle affords policymakers discretion in the decision-making process when there's the possibility of causing harm, but not the extensive scientific research to substantiate that risk.
There are two broad types of the Precautionary Principle - strong and weak.
In the strong version of the principle, costs are not considered in preventative action, and no level of environmental risk is acceptable, regardless of the economic or social benefits. A strong precautionary principle may also involve a mechanism by which those advocating for the action to be taken (and claiming its environmental/human health risks are nonexistent or low) are liable for any environmental harm that may result.
With a weak precautionary principle, there must be some evidence to suggest a given likelihood and severity of environmental harm. A weak precautionary principle takes into account the costs of precautionary measures as well as the benefits vs costs of such actions. In addition to scientific uncertainty, economic considerations can postpone action. The burden of proof falls on those advocating for the precautionary action, and there's no assignment of liability.
The alternate model is the “Risk-Based Principle”, which states that mitigating risk, but accepting some degree of risk, is more practical. On the non-governmental side, for example, the business community, and even the EPA to an extent, North America prefers this approach, whereas the other parts of the world, especially the EU, prefer the precautionary principle in terms of standards. For example, the debate in the International Organization for Standardization (ISO) between the two principles has been going on since 1992. Product and service standards written by ISO may typically incorporate one of the principles. Same for the development of rules and regulations. This is an important element of energy and climate standards.