And then came this number PM2.5: Atmospheric particulate matter, sociotechnical imaginaries, and the politics of air quality data

This article employs the concept of sociotechnical imaginaries to examine the broader political ecology of particulate air pollution, especially the connections between novel technoscientific practices of making pollution perceptible and data-driven modes of urban governance. Drawing on ethnographic material from Beijing, a city notorious for its pervasive smog, the article highlights the role of air quality data—such as particulate matter measurements (PM 2.5 ) and air quality indexes (AQI)—not only in informing citizens of the health-threatening air pollution but also in influencing new regimes of visibility and shaping practices of urban citizenship. Through the conceptual lens of sociotechnical imaginaries, the article shows that air quality data, increasingly shared digitally in the form of real-time continuous data streams, are not merely technoscientific indexes, nor are they value-neutral. Rather, their conceptualization is informed by technocractic visions of human-air relations and shaped by digital infrastructures. Learning from Beijing, the article argues that in order to generate an expanded understanding of the life-structuring effects of urban air pollution in the era of data-driven urbanism, political ecology of urban air needs to be considerate of how the numbers, which represent pollution, are conceptualized, amassed, and circulated, as well as what and whom they include or exclude.