BACKGROUND: Heavy industry emits many potentially hazardous pollutants into the air which can affect health. Awareness about the potential health impacts of air pollution from industry can influence people's risk perception. This in turn can affect (self-reported) symptoms. Our aims were to investigate the associations of air pollution from heavy industry with health symptoms and to evaluate whether these associations are mediated by people's risk perception about local industry. METHODS: A cross-sectional questionnaire study was conducted among children (2-18 years) and adults (19 years and above) living in the direct vicinity of an area with heavy industry. A dispersion model was used to characterize individual-level exposures to air pollution emitted from the industry in the area. Associations between PM2.5 and NOX with presence of chronic diseases (adults) and respiratory symptoms (adults and children) were investigated by logistic regression analysis. Risk perception was indirectly measured by worries about local industry (0-10 scale). Mediation analyses were performed to investigate the role of mediation by these worries. RESULTS: The response was 54% (2,627/4,877). In adults exposure to modelled PM2.5 from industry (per μg/m3) was related with reported high blood pressure (OR 1.56, 95% CI 1.13-2.15) and exposure to modelled NOX (per μg/m3) was inversely related with cardiovascular diseases (OR 0.91, 95% CI 0.84-0.98). In children higher PM2.5 and NOX concentrations (per μg/m3) were related with wheezing (OR 2.00, 95% CI 1.24-3.24 and OR 1.13, 95% CI 1.06-1.21 respectively) and dry cough (OR 2.33, 95% CI 1.55-3.52 and OR 1.16, 95% CI 1.10-1.22 respectively). Parental worry about local industry was an important mediator in exposure-health relations in children (indirect effect between 19-28%). CONCLUSION: Exposure from industry was associated with self-reported reported high blood pressure among adults and respiratory symptoms among their children. Risk perception was found to mediate these associations for ...