A Review on the Role of Urban Trees in Air Pollution Reduction

Abstract

Urban air pollution due to rapid urbanization and industrialization, is a serious threat to ecological stability and public health. The paper reviews studies across the world on the role of urban trees in accumulating particulate matter (PM) and reducing gaseous pollutants including sulphur dioxide (SO₂) and nitrogen dioxide (NO₂) through stomatal absorption. The fact that the effectiveness of this mitigation varies significantly by species demonstrates the importance of selecting suitable trees using the Air Pollution Tolerance Index (APTI). Ascorbic acid content, total chlorophyll, leaf extract pH, and relative water content are only a few of the biochemical indicators that make up this composite metric. Low-APTI species are bio-indicators, whereas high-APTI species are pollution "sinks." APTI-based selection is incorporated with ecological services (such as carbon sequestration and thermal regulation), morphological adaptations (such as canopy density and leaf texture), and urban barriers (such as allergenicity and infrastructure compatibility) in optimal urban forestry. Pollution abatement is further maximized through strategic planting patterns, spatial buffering close to sources of pollution, and maintenance techniques including pruning and improving soil health. This review suggests that species-specific green infrastructure is essential in order to improve urban air quality and human well-being. The Dhaka University Journal of Earth and Environmental Sciences, Vol. 15(1), 2026, P 15-25