Preliminary Findings of Heavy Metal Contents from Road Dust and Health Risk Assessments Towards a More Sustainable Future in Macao

Road dust contains a variety of heavy metals and is a widely used sustainability indicator for monitoring pollution and assessing environmental and health risks in sustainable development. Heavy metals in road dust mainly originate from worn-off particles from vehicles, such as tires, brake pads, road dust, and emissions from exhaust pipes. These heavy metal particles could remain on the road surface for a long period and cause environmental pollution. In this preliminary study, road dust was collected from 8 representative areas in Macao. The heavy metal content from road dust in Macao was extracted from each of the collected samples for an assessment of the heavy metal pollution and its potential threat to human health. The results show that heavy metals primarily originate from human activities, including transportation emissions (Mn: 67.37%, Zn: 57.01%, Sb: 54.1%) and industrial activities (Al: 84.70%, Fe: 76.71%, Pb: 65.32%). The metal-specific non-carcinogenic risk ranges from 1.17 × 10−7 to 2.65 × 10−5 and the total carcinogenic risk is 6.91 × 10−10, showing minimum health effects from heavy metals in road dust. Furthermore, there is a significant correlation between the total vehicle counts and the heavy metal contents such as Al, Si, As, V, and Fe (r = 0.50 to 0.82). This work represents the first characterization of heavy metal contents and risks of urban road dust in Macao.