The precautionary principle: Schutz and Wiedemann respond.

Salmony rightfully points to various examples for potentially harmful effects of human activities that call for strategies to cope with ambiguous risks. The precautionary principle is seen by many as the answer to this problem. We agree that the precautionary principle formulates a sensible maxim for coping with uncertainty. However, we are less confident that it provides a feasible solution.

There are at least two problems with the application of the precautionary principle. The first, which we addressed in our article (Wiedemann and Schutz 2005), is that applying the precautionary principle might have unintended and unwelcome effects--in our case, increase public concern about radio frequency electromagnetic fields (RF EMFs). At least when precautionary measures are implemented to reassure the public, this runs counter to the original intention.

The second, perhaps more serious, problem of applying the precautionary principle is its "extreme variability in interpretation" (Foster et al. 2000). The decision to apply the precautionary principle depends on three factors: the type of evidence considered as appropriate for decision making, the amount of evidence, and the reference point for triggering the precautionary principle (how much evidence is enough?).

Roughly, three different types of evidence can be distinguished: scientific data, observations of health professionals, and personal experiences of lay people. The problematic issue is that some proponents of the precautionary principle consider scientific information, although necessary and important, not to be the exclusive basis for decision making. However, expanding the data basis beyond scientific information may result in conflicting claims about the significance of the various types of evidence. And there are no efficient procedures to resolve these conflicts.

The key question is whether there is enough scientific evidence to show that the risk potential might be real. Although ignorance and uncertainty exist, at least some evidence is required for triggering precautionary measures (World Health Organization 2000). That is, a hazard must be identified, and some understanding is needed about the conditions under which it is likely to occur. Therefore, a careful assessment of the available evidence is critical.

At present, there is no dear definition of the reference point for the decision to invoke precautionary measures. Without this clarification, any decision on applying the precautionary principle remains arbitrary.

Obviously, the answer to this question cannot be given by science alone (although science can provide important information). It will require value judgments, and it is ultimately a political decision. However, even if policy makers are bold enough to vote for precaution, the question remains about what to do.

Any well-founded decision about precautionary measures will also require some knowledge about the effectiveness of the precautionary measures that are to be taken. Unfortunately, in those situations for which the precautionary principle is intended, this knowledge is usually lacking.

The decision to implement precautionary measures needs to be justified by more than pointing at the possibility that a risk may exist. It needs evidence, and above all, a structured and transparent procedure for evaluating this evidence. For this, a solution is pending.

The authors declare they have no competing financial interests.

Holger Schutz

Peter M. Wiedemann

Research Centre Julich

Programme Group MUT 

Julich, Germany

Email: [e-mail]

REFERENCES

Foster KR, Vecchia P, Repacholi MH. 2000. Science and the precautionary principle. Science 288(5468):979-981.

Wiedemann PM, Schlitz H. 2005. The precautionary principle and risk perception: experimental studies in the EMF area. Environ Health Perspect 113:402-405; doi:10.1289/ehp.7538 [Online 10 January 2005].

World Health Organization. 2000. Electromagnetic Fields and Public Health: Cautionary Policies. Geneva:World Health Organization. Available: http://www.who.int/docstore/ peh-emf/publications/facts press/EMF-Precaution.htm [accessed May 12 2005].