Building upon a detailed empirical analysis of the local understanding of hazards in one geographical area, in this paper we offer a critique of both the psychometric and 'risk society' approaches to the relationship between lay and scientific groups. Specifically, we explore the connection between lay understandings of risk and the contexts of their development and application with regard to one industrial hazard site in northeast England. Rather than presenting local knowledges as fixed or separable from cultural practices and social worldviews, we examine the relational and active construction of environmental understandings -- noting the significance of such factors as local memory, observation and evidence, definitions of expertise, risk and credibility, and moral discourses. The paper concludes with a discussion of the relationship between knowledge, understanding, and context. We also consider the wider significance of this case study both for environmental policy and for more theoretical treatments of science and its publics.