The difference between perceived and measured particulate matter in high population density urban environments : a citizen co-creation approach

Abstract

Understanding the way citizens perceive air quality and whether these perceptions correlate with actual air quality measurements is important for effective urban planning and policy. The perception–measurement gap and its dependence on context is well known in literature. The perception–measurement gap in dense Mediterranean urban environments remains comparatively less explored. This study aims at identifying the relationship between perceived and measured air quality in the dense urban locality of Gżira (Malta). A cocreative, citizen science approach was used that combines high resolution particulate matter (PM) monitoring with survey based perception and health data. Air quality measurements from nine distributed sensors and a survey of 212 respondents revealed a pronounced mismatch between objective measurements and subjective experience. Annual mean PM2.5 concentrations ranged from 7.8 to 10.1 μg/m3, while PM10 ranged from 8.4 to 12.1 μg/m3 which are well below European limits (approximately 40%–50% of limits for PM2.5 and 20%–30% for PM10). Notwithstanding this, a statistical analysis of survey responses indicated high levels of concern and a considerable proportion of the surveyed population associated their environment with negative physical and psychological health impacts. These results highlight that for dense urban environments, the perception– measurement gap may apply and environmental concern may be high despite the relatively small PM pollutant concentrations reported. In these cases, perception may be driven by other factors such as visible urban stressors including traffic and construction activity which were not directly measured in this study. Further work on the perception–measurement gap would be useful by means of more detailed measurements of social and air quality indicators.