Long-Term Spatiotemporal Patterns of Multi-Pollutant Air Quality Across Nigeria: A National-Scale Analysis of PM₂.₅, PM₁₀, NO₂, CO, O₃ and SO₂

Air pollution is one of the significant environmental and public health concerns across rapidly developing cities and regions of the world. In Nigeria, growing urbanization, industrialization and increasing energy demand have intensified concerns about air quality and its associating chealth implications. Despite this, comprehensive national scale studies of long-term behaviour of multiple air pollutants across different regions of the country remain limited. This study investigated the spatio-temporal variation of six key atmospheric pollutants (PM₂.₅, PM₁₀, NO₂, CO, O₃, and SO₂) across Nigeria over a twelve-year period (2012–2023). Data from twenty-four cities representing diverse climatic zones, ecological environments, and urban settings were analysed. Monthly pollutant concentrations were aggregated into annual means and examined using geospatial analysis and population-weighted exposure metrics to identify spatial patterns and pollution hotspots. The results showed a clear regional difference in pollutant distributions across Nigeria. Fine particulate matter (PM₂.₅) had persistent hotspots in the southeastern and Niger Delta regions, reflecting the influence of industrial activities, urban emissions, and secondary aerosol formation. In contrast, PM₁₀ concentrations are generally higher across northern Nigeria, largely driven by Saharan dust transport, Harmattan winds, and dry-season resuspension processes. Nitrogen dioxide and Sulphur dioxide display strong southern concentrations associated with petro-industrial activities, gas flaring, and major urban transport corridors. Carbon monoxide exhibits a broader spatial distribution, with elevated levels in both the southeastern industrial belt and parts of northern Nigeria, indicating the combined influence of incomplete combustion and seasonal biomass burning. Surface ozone shows a contrasting north–south gradient, with higher concentrations across northern regions where stronger solar radiation enhances photochemical production. The findings of this study highlight the combined roles of anthropogenic emissions, climatic variability, and atmospheric transport in shaping Nigeria’s air pollution patterns and provide valuable insights for air quality management and environmental policy development.