Assessing Sustainable Approaches to Urban Air Quality: A Study of Malaysia's Largest Conurbation Regions

The capital of Malaysia has undergone urbanization since the 1980s, which led to the formation of the largest conurbation area, Kuala Lumpur Extended Mega Urban Regions (KLEMUR). This study aims to understand the long-term air quality trends in KLEMUR, particularly concerning land use changes. Statistical and geostatistical analysis in the Geographic Information System (GIS) was used to analyze air pollutants (PM10, O3, NO, NO2, NOx, CO, and SO2) and land use data (built-up areas, vegetation, and water bodies). The results showed increased trends in air pollutants, except for SO2, which decreased due to improvements in fuel consumption. However, the annual mean concentration of PM10 exceeded both the Malaysian Ambient Air Quality Standard (MAAQS) and WHO guidelines. Despite COVID-19 lockdowns, PM10 concentrations remained above recommended limits. The time series results showed only PM10 and O3 were also influenced by the meteorological conditions during the seasonal monsoon. The Principal Component Analysis (PCA) results demonstrated that 53.61-63.42% of the total variance was influenced by motor vehicles and industrial emissions since the strong factor loadings (>0.70) consisted of NO, NO2, NOx, CO, and SO2. The KLEMUR air quality was predominantly affected by motor vehicle emissions since the NO/NO2 ratio exceeded 2.0. The KLEMUR land use increased in built-up lands (4.0%) and there was a simultaneous reduction in vegetation (3.3%) and water bodies (2.3%), causing the spatial distribution of air pollutants to expand from the centre of KLEMUR to the south and north. The KLEMUR land use has a significant impact on NO, NO2, NOx, CO, and SO2 since the air pollutants are positively associated with built-up lands and negatively associated with vegetation and water bodies. The Geographically Weighted Regression (GWR) model was able to determine that about 80–90% of the KLEMUR air pollution was influenced spatially by the changing of built-up lands and vegetation, while only 20–70% of water bodies influenced the air pollution. A sustainable air quality framework was proposed based on these findings by focusing more on land use changing impacts for sustainable cities and clean air without limiting economic growth.