Agential cuts of regulatory science practices – the case of microplastics

Over the past decades, a new field of research related to microplastics has emerged which still faces a high degree of uncertainty and conflicting views regarding the risks posed by microplastics. To date, social research has not addressed the regulatory science practices necessary for assessing the risks created by microplastics and related ethical questions. Therefore, the objective of this article is to analyse the role of central regulatory science practices, that is, risk assessments as they relate to microplastics. I draw on the work of Karen Barad to conceptualise these regulatory science practices as boundary-drawing practices which produce agential cuts. I will show that scientific and regulatory boundary-drawing practices draw agential cuts determining the properties of microplastics and regulatory actions that have ‘real’ consequences for human and environmental health. My empirical case demonstrates that different versions of risk assessment exist – one based on thresholds and the other on persistence – each of which have different regulatory consequences. Threshold risk assessment does not legitimise action to regulate microplastics, because the threshold at which microplastics have toxic effects requires such high concentrations that industry could continue to emit microplastics for decades. Therefore, only risk assessments that relate to the materiality of microplastics in terms of persistence and accumulation legitimise regulatory action.