Environmental justice struggles are increasingly contests waged over data and knowledge, involving claims of expertise and counter-expertise (Corburn 2003). A common observation is that a reliance on formal science elevates the data generated by accredited knowledge professionals to a prime political position, ‘leaving little or no room for the layperson’ (Fischer 2000: 51; Yearley 2000). This results in a growing tension between those who have ‘knowledge’ and those who do not, as well as the active re-negotiation of those categories (Wiebe 2013). Residents of pollution hotspots and their allies in the environmental justice movement make a normative claim for valuing the expertise of residents themselves in detecting and measuring pollution and its effects on environmental health (Brown 1992; Cole and Foster 2001; Di Chiro 1998; Shepard et al. 2002). But the institutions of formal law do little to resist the notion that the ‘most legitimized forms of knowing the human body require the instruments and institutions of science and medicine’ (Alaimo 2010: 27). In truth, of course, none of these is immune to culture or ideology, and none can escape their social origins. As Sargent and Wilke demonstrate in very different contexts in their chapters in this volume, the laws and institutions driving the collection of the ‘data’ and assigning it social meaning further manipulate it in ways that render it opaque to those most invested in the outcomes it produces.