Contrasting norms on the use of evidence in risk assessment: the controversy surrounding the carcinogenicity of glyphosate

Glyphosate is the most widely used herbicide in the world, used in farming as well as home gardening since the mid ‘70 s. For decades it was considered by regulators an ‘ideal’ pesticide: deadly to pests, respectful of humans. In 2015, it unexpectedly became highly controversial because of conflicting scientific assessments of its carcinogenic effects. On the one hand the UN International Agency for Research on Cancer (IARC) classified glyphosate as ‘probably a carcinogen’; on the other the European Food Safety Authority (EFSA) concluded that glyphosate should be classified as ‘not a carcinogen’. In this I article I develop an explanation for differences in the assessments made by these two regulatory agencies. Whereas most sociological explanations for regulatory disagreements focus on cultural and organisational factors, in this article I advance a normative institutionalist explanation for differences in the outcome of risk assessments. Accordingly, I posit that formal norms regulating the procedures for appraisal directly affect the final outcome by establishing the criteria for the type, quantity and quality of evidence assessed. On the basis of the glyphosate case study, the article discusses advantages and shortcomings of different procedural norms for the selection and evaluation of scientific evidence, and their implications for the overall quality of risk assessments.