Citizen Perception of Air Pollution and the Role of Urban Trees as Biomonitoring Agents of Cadmium and Lead in the Guadalajara Metropolitan Area, Jalisco, Mexico

Heavy metal pollution in urban environments and public understanding of these contaminants pose major challenges for air-quality management. Urban trees have been proposed as tools to mitigate air pollution; however, evidence integrating biophysical assessments and social perception is still limited in the Guadalajara Metropolitan Area (AMG), Mexico. This study evaluated Cd and Pb accumulation in the leaves of five common urban tree species and assessed residents’ perceptions of air pollution and the role of urban trees. Significant interspecific differences were found, with Citrus × aurantium L. showing the highest Cd concentration (2.60 mg kg−1) and Bauhinia variegata L. the highest Pb content (7.45 mg kg−1). Socially, 62% of respondents found the AMG to be one of the most polluted metropolitan areas in the country, and >90% acknowledged direct or indirect health impacts associated with air pollution; nevertheless, a marked knowledge gap persisted about specific contaminants such as Cd and Pb. This “perception paradox” highlights an opportunity to strengthen risk communication and environmental education and suggests that urban-tree biomonitoring can provide locally meaningful evidence to support public engagement and policy actions. Taken together, the environmental and social findings provide an interpretive, metropolitan-scale synthesis that informs air quality management and public health protection in the AMG.