Abstract
Grassroots, bottom-up citizen science is a burgeoning form of public engagement with science, in which citizens mobilize scientific data to address local and global concerns. Contrary to top-down citizen science projects in which citizens collect data for experts, these grassroots initiatives typically unfold in do-it-ourselves fashion, thereby challenging formally-sanctioned, expert-centric citizen science approaches. This article illustrates these points through a comparative analysis of two potentially paradigmatic sites for environmental grassroots citizen science: Safecast (radiation pollution; Japan) and CuriousNoses (air pollution; Flanders, Belgium). These cases are selected on the basis of their anchors in local self-organized communities, with each case initiated by citizens instead of by formal institutions. Adopting a relational account of these sites as being shaped through both top-down and bottom-up imperatives, we draw out key features (defining moments, key actors, discourses, devices) in the constitution of these networks as credible, potentially influential actors in affairs of environmental governance. We introduce the notion of “citizen sciencization” as a way of understanding and exploring these processes against the backdrop of changing science-society relationships in Japan and Europe.