Abstract

Urban air pollution remains a critical global public health challenge, driven largely by accelerated urbanization, 
industrial expansion, and increasing energy demands. This narrative review synthesizes existing evidence on the 
characteristics, sources, and health impacts of urban air pollutants, emphasizing particulate matter, nitrogen 
oxides, sulfur dioxide, ozone, ultrafine particles, and emerging contaminants such as microplastics. Drawing on 
historical perspectives, the review highlights the evolution of scientific understanding from early smog events to 
contemporary concerns involving complex pollutant mixtures and systemic health impacts. The review also 
explores measurement and monitoring strategies ranging from fixed-site stations to mobile sensors and integrated 
modeling, which shape exposure assessment and epidemiological research. Evidence consistently links urban air 
pollution to cardiovascular, respiratory, neurological, immunological, and perinatal health outcomes, with 
children, older adults, socioeconomically disadvantaged groups, and those with underlying disease identified as 
particularly vulnerable. Mechanistic pathways, including inflammation, oxidative stress, endothelial dysfunction, 
and neuroinflammation, provide biologically plausible explanations for observed risks. The review further assesses 
public health interventions, including urban planning, transportation policies, emission reduction strategies, and 
risk communication frameworks. Despite advancements in regulatory standards, clean technologies, and 
surveillance systems, substantial inequities persist across urban populations, particularly in low- and middle
income countries. Strengthening interdisciplinary approaches, improving exposure assessment, and addressing 
emerging contaminants are essential to reducing the global urban air pollution burden.