Visualization Study on Trends and Hotspots in the Field of Urban Air Pollution in Metropolitan Areas and Megacities: A Bibliometric Analysis via Science Mapping

Air pollution poses a significant challenge to environmental sustainability and inhibits economic and social development. In urban areas, the combined effects of high population density, industrial concentration, and the urban heat island effect make pollution control even more complex and demanding. Most studies on urban air pollution focus on specific pollution sources or localized areas, lacking a systematic approach tailored to the unique environmental conditions of megacities. Herein, this study employs bibliometric analysis based on the Web of Science (WOS) Core Collection, incorporating 3109 research articles on urban air pollution, including metropolitan areas and megacities, published between 2000 and 2024. By constructing a knowledge framework, this research reveals the thematic networks and evolutionary trends in the air pollution field. The findings indicate that key research themes, such as aerosols, air quality, and urban heat islands, have emerged as focal points. These themes, while relatively distinct, are interconnected, forming a three-dimensional framework of pollutants–health effects–monitoring, and governance. Moreover, the disciplinary network exhibits a clear convergence trend, with a shift from single-discipline studies to a more interdisciplinary approach. In terms of international collaboration, a bipolar structure led by the United States and China has taken shape. Through a multidimensional analysis of urban air pollution, this study identifies research hotspots and highlights the critical role of interdisciplinary and international cooperation in advancing urban air pollution control. By addressing the gap in cross-disciplinary, multi-perspective research, this work enhances the overall understanding of urban environmental policies and provides valuable insights for promoting global urban sustainability.