Differences in the strengths of evidence matters in risk–risk trade-offs

Making decisions between alternatives are challenging when there is weak or unreliable knowledge about the risks and benefits of the alternatives. This requires a trade-off between risks (and benefits). Here, we comment on a recent paper on risk–risk trade-offs and highlight the difficulties of making such trade-offs when the available evidence is of different strength. One current example of a risk–risk trade-off under weak evidence is the restriction and reevaluation of the risks of neonicotinoid insecticides to bees conducted by the European Food Safety Authority (EFSA). We argue that a risk–risk trade-off is essential in this context. Although considerable research efforts have been focused at determining the risks of neonicotinoids to bees, the evidence base is still limited. However, focus on strengthening evidence on impacts of one substance may lead policy-makers and public to believe that its substitutes are less harmful, when in fact evidence is weak on the impacts of these substitutes as well. We argue that a broader management of uncertainty is needed and that the difference in uncertainty underlying evidence of risk for different alternatives needs to be communicated to policy-makers. We suggest that this can be done, for example, using measures of uncertainty, which take into account strength in evidence, and combine these with principles to guide decision-making.