Precautionary Principle - Oxford Reference

Subscriber Login

  • This account has no valid subscription for this site.

Forgotten your password?

In This Entry

More on this Topic

Page of

PRINTED FROM OXFORD REFERENCE ( (c) Copyright Oxford University Press, 2013. All Rights Reserved. Under the terms of the licence agreement, an individual user may print out a PDF of a single entry from a reference work in OR for personal use.

Subscriber: null; date: 04 May 2016

Precautionary Principle

The Oxford Companion to Global Change

Daniel Bodansky

Precautionary Principle 

The precautionary principle is a legal and policy principle addressing the problem of scientific uncertainty in environmental decision-making. Although numerous formulations have been advanced, the core idea is expressed in the familiar adage, better safe than sorry. The principle has implications for both the timing and substance of environmental measures: states should anticipate and respond to potential environmental harms, rather than only known or proven harms, and environmental risks should be managed with a margin of error in case they are more serious than originally expected.

The importance of precaution is recognized in many national environmental laws—for example, the 1970 U.S. Clean Air Act, which requires regulators to apply an “ample margin of safety” in setting emissions limits for hazardous pollutants—and is reflected in international actions such as the 1982 moratorium on commercial whaling. However, as an explicit precept, the precautionary principle originated in Germany and made its way into international environmental law in the mid-1980s. The principle has been included in numerous policy declarations, as well as in most recent environmental treaties, including the Climate Change and Biological Diversity conventions. [See Biological Diversity and Climate Change and Societal Development.] The most widely cited international formulation is Principle 15 of the 1992 Rio Declaration on Environment and Development, which states:

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.

The precautionary principle's applicability is a function of both the severity and the evidence of environmental risk. Most formulations of the principle address these issues only in somewhat general terms. Typically, application of the principle is limited to risks of serious or irreversible harm. With regard to evidence, lack of full scientific certainty is not an excuse for delay. Instead, precautionary action depends only on prima facie grounds for concern. Some formulations assert more specifically that precautionary action is warranted when there is knowledge that an effluent is persistent, toxic, and liable to accumulate in the environment, even though no environmental harm has yet been proven, or when there is knowledge of an environmental harm, even though the causal link with an activity is only suspected, not proven.

Like other international environmental principles such as sustainable development and intergenerational equity, the precautionary principle does not dictate particular environmental measures but serves instead as a general orientation or guide. Different formulations frame the principle in more or less absolute terms. The Rio Declaration incorporates the notion of cost-benefit balancing, but some treaty formulations are oblivious to cost. At a minimum, the precautionary principle would appear to entail environmental-impact assessment. Beyond that, a precautionary approach may involve clean production techniques, best available technology, or a reversal of the burden of proof. An example of the latter is the reverse-listing procedure of the 1996 Protocol to the London (Dumping) Convention, which forbids the dumping of wastes at sea unless a material is specifically determined to be safe.

Outside the context of treaty law, the legal status of the precautionary principle is controversial. Although the principle has been included in many international agreements and policy declarations, as well as in European Union law and some national statutes and court decisions, scholars disagree about whether the principle has attained the status of customary international law, given the variety of formulations and the lack of consistent national practice.


Bodansky, D. “Scientific Uncertainty and the Precautionary Principle.Environment 33.7 (1991), 4–5, 43–44. A critical appraisal of the precautionary principle's ambiguities and difficulties of application.Find this resource:

    Cross, F. B. “Paradoxical Perils of the Precautionary Principle.Washington and Lee Law Review 53 (1996), 851–925. Criticism of the precautionary principle as a simplistic rhetorical device that may increase rather than decrease overall environmental risk.Find this resource:

      Freestone, D., and E. Hey, eds. The Precautionary Principle and International Law. The Hague, London, and Boston: Kluwer, 1996. An excellent collection of essays focusing on how to put the precautionary principle into practice.Find this resource:

        Hickey, J. E., Jr., and V. R. Walker. “Refining the Precautionary Principle in International Environmental Law.Virginia Environmental Law Journal 14 (1995), 423–454.Find this resource:

          Kriebel, D., et al. “The Precautionary Principle in Environmental Science.Environmental Heath Perspectives 109.9 (2001), 871–876.Find this resource:

            O’ʾRiordan, T., and J. Cameron, eds. Interpreting the Precautionary Principle. London: Cameron May, 1994. A multidisciplinary collection of essays on scientific, policy, and legal aspects of the precautionary principle.Find this resource:

              Daniel Bodansky

              Was This Useful?