West Africa is one of the most poorly monitored regions in the world, and is one of the largest contributors to ambient air pollution-related premature death and morbidity. This systematic review brings together and syntheses peer-reviewed and grey literature from the past 8 years (2018-2026) with a particular interest on innovations in air quality monitoring in the Economic Community of West African States (ECOWAS) member states. A search, based on PRISMA criteria, of Google Scholar and various other databases, was conducted to identify relevant, geographically accessible and methodologically transparent sources, which were then synthesized in a narrative format to provide a broad overview of the literature on the topic. The four main categories of innovation identified were: 1) low-cost sensor networks (both optical and electrochemical), 2) machine learning sensor calibration, 3) satellite-derived and hybrid PM2.5 mapping, and 4) citizen science and community-based monitoring. Reference-grade monitoring is limited to a few countries (mostly Senegal) and somewhat less in Ghana, Togo, C？te d’Ivoire, Burkina Faso and Niger, while low-cost sensor deployments have grown rapidly in Nigeria as well as in these countries. With a lack of reference infrastructure, the use of machine-learning calibration tools and satellite-fusion products is growing to satisfy the called-for compensation. Compared to East Africa, the citizen science movement is still in its infancy in ECOWAS. Challenges that persist include a lack of legislation, disorganized funding, poor technical skills to maintain and calibrate sensors and poor sensor data integration with the public health and regulatory systems. The review concludes with recommendations for the development of regional data sharing infrastructure, harmonized calibration procedures, and investment in hybrid monitoring architectures of reference stations, low-cost sensor networks and satellite products for continued monitoring.
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