Considering risk assessment up close: The case of bovine spongiform encephalopathy

Risk assessment studies often adopt a quantitative approach and analyse decisions or judgements in relation to risk at one specific point in time. These studies certainly have their merits but their preponderance in the literature on risk has been to the exclusion of qualitative studies that seek to examine judgements of subjects over an extended period of time. I seek to redress this imbalance by examining how scientists assessed risk in the context of a significant public health problem in the UK: the emergence of bovine spongiform encephalopathy (BSE) in cattle. This disease first emerged in British cattle in 1986. Yet over 20 years on, its implications for human health are still being assessed by scientists. In this paper, I examine the reasoning strategies that scientists employed to make risk assessments in relation to BSE in the period between 1986 and 1996. Two arguments in particular (analogical argument and the argument from ignorance) were the mainstay of scientific reasoning in the period under investigation. The rational standing of these arguments varied over time in relation to evidence that was emerging from experimental and other studies. It is argued that it is not possible to capture the factors which are necessary to understanding scientific risk assessments in relation to BSE within the type of quantitative, static study that is typically pursued within research on risk.