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Precautionary principle

Human life is full of risks which we have to deal with. Science and technology can help in diminishing some risks of nature, as it is the case, for example, with life expectancy. On the other hand, science and technology have also contributed to the creation of new threats to human existence or quality of life. The emergence of increasingly unpredictable, uncertain and unquantifiable but possibly catastrophic risks has confronted societies with the need to develop an anticipatory model in order to protect humans and the environment against these uncertain risks of human action: the precautionary principle.

The precautionary principle traces its origins to the early 1970s in the German principle ‘Vorsorge’, or foresight, based on the belief that the society should seek to avoid environmental damage by careful forward planning. The ‘Vorsorgeprinzip’ was developed into a fundamental principle of German environmental law and invoked to justify the implementation of robust policies to tackle acid rain, global warming and North Sea pollution. The precautionary principle then flourished in international statements of policy. On a national level, several countries have used the precautionary principle to guide their environmental and public health policy. In the United States e.g., the precautionary principle is not expressly mentioned in laws or policies. However, some laws have a precautionary nature, and the principle underpins much of the early environmental legislation in this country (The National Environmental Policy Act, The Clean Water Act, and The Endangered Species Act).

The precautionary principle is based on the adage that ‘it is better to be safe than sorry’. However, there is no universally accepted definition of the principle. The Rio Declaration 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 (Rio Declaration 1992, Principle 15).

A stronger definition can be found in an EU communication:

The precautionary principle applies where scientific evidence is insufficient, inconclusive or uncertain and preliminary scientific evaluation indicates that there are reasonable grounds for concern that the potentially dangerous effects on the environment, human, animal or plant health may be inconsistent with the high level of protection chosen by the EU (EU, 2000).

Each formulation of the precautionary principle shares the common prescription that scientific certainty is not required before taking preventive measures. Moreover, most versions involve some degree of burden shifting to the promoter of an activity or product. However, it is important to note that none of definitions answer the question of the amount of precaution to apply in a given circumstance. In the case of the Amazon, we know that deforestation damages biodiversity although we remain unaware of many of the species that are disappearing (and much less of how we can estimate an economic value for such losses). We also know that deforestation contributes to the enhanced greenhouse effect although we do not know the exact effects of increases in temperature.

The precautionary principle is relevant to many issues, especially those of environment and public health, global warming or sharp climate change, extinction of species, the uncertain risks of nuclear power or geoengineering, the introduction of new and potentially harmful products into the environment that threaten biodiversity (e.g., genetically modified organisms), threats to public health due to new diseases or techniques (e.g., AIDS transmitted through blood transfusion), persistent or acute pollution (asbestos, endocrine disruptors, etc.), food safety (e.g., Creutzfeldt-Jakob disease), and other new bio-safety issues (e.g., artificial life and new molecules).

Besides its apparent simplicity, the principle has given rise to a great deal of controversy and criticisms, notably:

  • The precautionary principle is said to not be based on sound science. In this sense, critics claim that decision-makers are sometimes selective in their use of the precautionary principle, applying it for political reasons, rather than scientific reasons.
  • When applying the principle, society should establish a threshold of plausibility or scientific uncertainty before undertaking precautions. Indeed, no minimum threshold is specified across the definitions so that any indication of potential harm could be sufficient to invoke the principle. Most times, a ban on the product or activity is the only precaution taken.
  • Another often-raised criticism points to the potentially negative consequences of its application; for instance, a technology which brings advantages may be banned because of its potential for negative impacts, leaving the positive benefits unrealized.
  • Some say that the precautionary principle is impractical, since every implementation of a new technology carries some risk of negative consequence.


EU (2000) Communication from the commission on the precautionary principle, COM1, Brussels: Commission of the European Communities.

Rio Declaration (1992) Report of the United Nations Conferences on Environment and Development, Rio de Janeiro, 3-14 June1992, Annex I, Rio Declaration on Environment and Development.  (Available from

For further reading

Hanson, M. (2003) The precautionary principle, in: Page, E.A. & Proops, J. Environmental Thought, Cheltenham (UK), Edward Elgar, 125-143.

Paterson, J. (2007) Sustainable development, sustainable decision and the precautionary principle, Nat Hazards, 42, 515-528.

This glossary entry is based on a contribution by Tom Bauler

EJOLT glossary editors: Hali Healy, Sylvia Lorek and Beatriz Rodríguez-Labajos

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