Science and the Precautionary Principle

The precautionary principle is a regulatory approach, under conditions of scientific uncertainty, requiring that a new chemical or technology be regulated or banned until it is proven safe. This principle was developed in opposition to the dominant regulatory standard, which requires affirmative evidence of harm before regulatory action can be taken. These two approaches designate a central conflict in environmental and food regulation, particularly related to chemical release and use of genetically modified organisms.

Precautionary approaches to regulation have existed for much of the past century. For example, the United States Food and Drug Administration works on a precautionary model for drugs and food additives. Thus, pharmaceutical companies cannot market a drug in the United States until it is explicitly approved following affirmative evidence of safety.

Precaution as an explicit principle of policy making has more recent origins. It arose out of 1970s German environmental policy, particularly the Vorsorgeprinzip (foresight principle). In international regulation it was first codified in the 1984 First International Convention on Protection of the North Sea. Its most important articulation may be found in the Rio Declaration of the 1992 UN Conference on Environment and Development, which states in Principle 15 that the ”lack of full scientific certainty” should not prevent environmental protection. Other influential statements on precaution can be found in the 1998 ”Wingspread Statement on the Precautionary Principle” and a 2000 ”Communication from the Commission of the European Communities on the Precautionary Principle.” Several countries have explicitly endorsed the precautionary principle, most notably the European Union in the 1992 Treaty of Maastricht.

While naming an approach to scientific evidence, the precautionary principle is associated with a general orientation toward regulation that is directly counter to the ”risk paradigm” or ”sound science” approach. It is a crucial feature of what Martin Hajer calls the ”ecological modernization” discourse coalition, and Joe Thornton treats it as part of the ”ecological paradigm” of regulation, thus supporting a particular orientation toward scientific uncertainty, risk, expertise, proof, regulation, responsibility, public participation, and progress. As such, it is tied up with the politics of modernity and the culture wars: precaution is often favored by environmental, health, and consumer activists and advocates who support greater regulation; risk is often favored by corporations and free trade advocates who prefer minimal regulation.

Most proponents of precaution favor prevention rather than management (control and remediation) of pollution, are skeptical of scientific claims and standards in arenas of extreme complexity, respect democratic input as an important adjunct to technical knowledge, seek to regulate classes of phenomena rather than individual chemicals or products, question the assimilative capacity of the environment, prefer known to unknown risks, and would require proof of safety from the producer of a new product (often called a reversed onus of proof). They also favor Type I errors (false positives for harm) rather than Type II (false negatives).

By contrast, the risk paradigm generally takes a ”command and control” approach to regulation, which focuses on defining ”acceptable discharge” rates. This paradigm admits a relatively narrow set of quantifiable and measurable risks for consideration; that is, risks to human health and the environment rather than economic, cultural, or community risks. It thus supports expert driven and technocratic modes of regulation. The refusal to regulate based on uncertain knowledge derives from a positivist stance toward science that buttresses their claim that this is the only ”sound science” approach to regulation.

Proponents of precaution reject the ”sound science vs. anti-science” designation. Neither formulation is inherently more scientific than the other, although they do understand regulatory science differently – as either positivistic or as inherently uncertain. Precautionary approaches also tend to treat science policy as a science/politics   hybrid,   whereas   risk based approaches appeal to the separation (purification) of science and politics into separate realms.

These paradigms are discursive packages rather than logical constructions, and as such can be reconstructed. Ongoing attempts at harmonizing these approaches seek to recombine various elements in a number of different ways. Some proponents of the precautionary principle fear that it will be co-opted as it is thus separated from its historical entailments.

Both risk based and precautionary approaches have logical extremes, which would make the policy untenable in practice. Positive proof of harm is very rare, and thus an absolutist risk perspective effectively undermines regulation. Critics of risk based regulation claim that this is currently the case for persistent, bioaccumulative, and synergistic chemicals and those with complex or non linear modes of action in human and environmental systems. Ecosystem theories and theories of endocrine disruption in particular raise such concerns (the endocrine disruption hypothesis posits that many synthetic chemicals have powerful hormonal effects at extremely low doses). Likewise, positive proof of safety is very difficult, suggesting that no new chemical or genetically modified organism could be approved under precaution. Proponents of strong precaution suggest that most synthetic chemicals have historically proven harmful to human health and the environment, so such an approach is warranted. Critics suggest that this approach is completely untenable and would ultimately stall all innovation, costing many more lives than it would save. Most proponents of precaution reject such extremes, suggesting instead that precaution shifts the calculus of regulation rather than providing a specific legal rule against innovation. Some suggest that precaution should be invoked only when there exists a prima facie case for the danger of a new substance and that priorities for precautionary regulation should be based on the degree of scientific uncertainty in combination with degrees of possible harm.


  1. Goklany, I. (2001) The Precautionary Principle: A Critical Appraisal of Environmental Risk Assessment. CATO Institute, Washington, DC.
  2. Hajer, M. A. (1995) The Politics of Environmental Discourse: Ecological Modernization and the Policy Process. Clarendon Press, Oxford and New York.
  3. Harremoes, P., Gee, D., Mac Garvin, M., Stirling, A., Keys, J., Wynne, B., & Vaz, S. G. (Eds.) (2002) The Precautionary Principle in the 20th Century: Late Lessons from Early Warnings. Earthscan, London.
  4. Levidow, L. (2001) Precautionary Uncertainty: Regulating GM Crops in Europe. Social Studies of Science 31: 842-74.
  5. Martuzzi, M. & Tickner, J. A. (Eds.) (2004) The Precautionary Principle: Protecting Public Health, the Environment, and the Future of Our Children. World Health Organization Europe, Copenhagen.
  6. Raffensperger, C. & Tickner, J. (Eds.) (1999) Protecting Public Health and the Environment: Implementing the Precautionary Principle. Island Press, Washington, DC.
  7. Thornton, J. (2000) Pandora’s Poison: Chlorine, Health, and a New Environmental Strategy. MIT Press, Cambridge, MA.

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