Microplastics trouble conventional geographies of pollution. Released from domestic routines, industrial processes, road infrastructures, and consumer products, they travel through wastewater systems into treatment plants, sewage sludge, agricultural soils, rivers, and aquatic environments. This article examines the emerging European Union requirement to monitor microplastics in wastewater, introduced through the revised Urban Wastewater Treatment Directive. Drawing on interviews, document analysis, and fieldwork in wastewater treatment and laboratory settings, we analyse monitoring as a governance device in the making. We show that monitoring does not simply detect a pre-existing environmental problem. Rather, it co-produces what microplastics become as objects of knowledge, intervention, and responsibility. The article traces how the purpose of monitoring remains unsettled, oscillating between precaution, public visibility, future regulation, and source attribution. It then shows how seemingly technical choices around sampling, detection limits, and particle- or mass-based methods produce specific regimes of visibility and invisibility. These choices have spatial consequences: they shape where pollution is located, whether responsibility is directed upstream toward production and consumption or downstream toward treatment infrastructures, and which interventions become thinkable. The article contributes to debates on infrastructure, environmental governance, and spatial accountability by showing how monitoring reorganises pollution in time and space.

Publication:

Muenster, Noah, and Ulrike Felt. 2026. “Governing Residues in Motion: Microplastics Monitoring, Wastewater Infrastructures, and the Spatial Politics of Accountability.” under review.

How do emerging environmental phenomena become actionable amid scientific uncertainty and public urgency? This article argues that to understand how microplastics become governable, we must study classification as a central site where matters of fact, concern, and care are composed. Drawing on comparative assemblage ethnography across scientific conferences, public debates, and European regulatory processes, we trace how microplastics are enacted as epistemic, public, and regulatory objects. In scientific practice, object-centered classifications aim at rendering heterogeneous particles measurable and comparable. In public arenas, labeling condenses plurality into a recognizable and affectively charged issue. In regulatory contexts, source-centered and legally operational categories reorganize the phenomenon into governable segments. These are not translations of a stable object—microplastics—but distinct enactments shaped by different evidentiary standards and institutional constraints. The case shows that classification under conditions of ontological instability does not necessarily lead to closure but enables coordination. We show how governance materializes through classificatory infrastructures that stabilize relations between fact, concern, and care without resolving epistemic indeterminacy. Classification is a political technology through which environmental objects are rendered actionable in the absence of settled knowledge.

Publication: 

Muenster, Noah, and Ulrike Felt. 2026. “Making Microplastics Matter: Classification, Politics and the Lives of Microplastics as Environmental Objects.” Social Studies of Science.

Small plastic debris in ocean environments have been discussed in scientific literature the first time in the early 1970s. However, they have only gained public and policy attention in the last decade. In the EU, concern about microplastics became mainstream with the European Circular Economy Action Plan published by the European Commission in December 2015. Governing microplastics is not only challenging because of the ubiquity of microplastics in the environment, but also due to diversity of materials that fall under this label, their diverse sizes, forms and chemical compositions and a lack of clear classification and standardized measurements.

We will investigate how microplastics become a matter of concern for the EU and how it is transformed into a “European policy object” with all the challenges this brings with it. This means carefully analysing the ecosystem of EC documents in an effort to see how microplastics as a key residue is framed as a matter of concern and how it is turned into a matter of care through regulation.

This has so far led to two publications: 

Felt, Ulrike, and Noah Muenster. 2026. “Navigating regulatory complexities: Challenges and shifting problem framings in turning microplastics into a European policy object.” Cambridge Prisms: Plastics 4. doi: 10.1017/plc.2026.10048.

Matthies, Kaye. 2025. “Microplastics are not microplastics are not microplastics”: Making microplastics in the EU regulatory environment