A ‘Richter scale for risk'? Scientific management of uncertainty versus management of scientific uncertainty

There have recently been calls in the UK for the development of a ‘Richter scale for risk’. It is helpful when considering the merits of these proposals to distinguish three categories of risk: directly perceptible risk, e.g. climbing a tree, riding a bicycle; risks perceptible with the help of science, e.g. cholera and other infectious diseases; and virtual risks, about which scientists do not know or can not agree, e.g. BSE/CJD and suspected carcinogens. The professional management of directly perceptible risks is made difficult and frustrating by people insisting on being their own risk managers, and overriding the judgements of risk experts and the interventions of safety regulators. Risks perceived through science are framed in terms of probabilities. The Richter scale for risk seeks, by means of a table of ‘benchmark risks’, to help scientists communicate thier knowledge of risk to the lay public. But frequently these probabilities are nothing but confident sounding expressions of uncertainty. We do not respond blankly to uncertainty; we impose meanings upon it, and act upon these meanings. Virtual risks mayor may not be imaginary – but they have real consequences. The diverse responses to the inconclusive scientific evidence about issues such as BSE, pesticide residues, low level radiation, and global warming indicate that virtual risks are perceived through different cultural filters. The incoherent and inconclusive debates about such issues suggest the need for a better understanding of these filters.