Communicating the absence of evidence for microplastics risk: Balancing sensation and reflection

Communicating scientific evidence to decision makers and other stakeholders is an important task for scientists (SAPEA, 2019a, SAPEA, 2019b; Environmental and Health Risks of Microplastic Pollution, 2019). In this context, and specifically referring to recent evidence reviews on microplastics (SAPEA, 2019b, World Health Organization, 2019). Leslie and Depledge (2020) argue that both SAPEA (a consortium of European academies, part of the European Commission’s Scientific Advice Mechanism) and the UN’s World Health Organisation make the mistake of “assuming risk is absent in the absence of evidence”.
In what follows, we reflect on their criticism and raise some broader issues about communicating science on an emerging issue. We make four points. Of the four, the first two reply directly to Leslie and Depledge. The third point briefly discusses the philosophical issue of whether, and to what extent, an absence of evidence constitutes evidence of absence, a topic whose origins can be traced back to the Enlightenment philosopher Locke (1689/1823). The fourth point provides a broader perspective on science communication for policy.
We focus largely on Leslie and Depledge’s criticisms of the way the SAPEA report on microplastics (SAPEA, 2019b) was communicated, although we expect that similar responses might be made to their criticisms directed towards the WHO. Our effort is of course undertaken in Locke’s spirit of “the common offices of humanity and friendship in the diversity of opinions” (Locke, 1689/1823).