Abstract
This work examined the efficacy of passive air pollution mitigation measures (green infrastructure) in elderly care centres (ECCs) located around heavily-trafficked roads. We measured indoor and outdoor PM2.5 concentrations of three ECCs near major roads. We found that the highest PM2.5 concentrations were usually occurred during peak traffic. ECC3 (295 ± 67 μg m−3) exhibited the highest concentrations, presumably because of the shortest width of tree space (10 m) between the ECC and the road, followed by ECC2 (184 ± 38 μg m−3) and ECC1 (60 ± 16 μg m−3) having a distance of 40 and 105 m, respectively, covered by the park with dense trees in between. These results suggest that a wide space of trees between the ECC and the road was conducive to improving air quality. There is a strong positive correlation between traffic volume and outdoor PM2.5 concentrations of ECCs. Additionally, higher wind speed and temperature, along with lower relative humidity (RH), were linked to favourable conditions for reducing concentrations. Furthermore, measured indoor and outdoor concentrations were strongly correlated. The indoor/outdoor ratio decreased as the distance between the ECC and the road increased. The hazard ratio (HR) of the ECC, with 10 m wide of trees between it and the road, was respectively 38% and 80% higher than that with 40 m and 105 m wide space of dense trees between roads and ECCs. A trade-off exists between air quality in ECCs, transportation convenience and urban design. Consequently, to minimise the negative effects of traffic emissions, ECC should preferably be located away from heavily trafficked roads and near green infrastructure.