In the last decade, many arguments have emerged for encouraging public participation in environmental policy making and management While some have argued that, in democratic societies, people simply have a right to a participatory role, others base arguments for public participation on the idea that lay people may have access to knowledge which is unknown to officially sanctioned experts. Local people may count as experts about aspects of their neighbourhood or they may have insights into the behaviour of plant operators (...) that is thought to give rise to pollution. This paper reports on a novel empirical approach to analysing and capturing such 'lay' understandings. This technique, developed in ESRC-funded work in the UK, uses community mapping exercises in urban centres to produce spatial representations of local knowledges about air pollution and related problems of noise and odour. In the paper the technique is outlined, presenting data from the three-city case study. The paper concludes by assessing the ways in which participatory modelling can contribute to the local governance of air quality. (shrink)