A review of urban dust pollution in Iranian cities with examples from other parts of the world

Urban dust is the primary cause of spreading some contaminants, including potentially toxic elements (PTEs), polycyclic aromatic hydrocarbons (PAHs), and microplastics (MPs), in urban environments. Growth in population, industrial activities, and transport systems are evidently associated with elevated levels of these pollutants found in urban dust and the surrounding environment. These contaminants possess carcinogenic and accumulative characteristics, which can lead to various environmental and health problems. The primary objective of this study is to review recent studies on urban dust pollution in Iranian cities, as well as addressing relevant cases from other areas around the world. Within Iranian urban dusts, Pb, Cu, and Zn were the most polluting elements. The concentrations of Σ16 PAHs also showed a wide range of variation, primarily consisted of four-ring PAHs such as Pyrene, Fluoranthene, and Acenaphthene. The dominant forms of MPs in dust were fibers and granules fragments, with various colors including white-transparent, red, or black. The main sources of pollution in Iranian urban dusts are traffic-related contaminants, such as direct emissions from exhaust and the wearing of brake pads and tires, as well as industrial activities. Since identifying the pollutant sources is critical in the context of pollution mitigation and remediation, potential pollutant sources in urban dust were discussed in this review. Furthermore, some potential directions for future studies have been suggested to develop and implement effective monitoring strategies for contaminants in urban dust.