Ambient air pollution remains a major environmental and public health issue in rapidly industrialising cities, particularly in oil-producing areas such as Port Harcourt in the Niger Delta, Nigeria. This study evaluated ambient air quality and related health risks at selected sites representing industrial, traffic-heavy, residential, and semi-urban environments within the Port Harcourt metropolitan area. Levels of key atmospheric pollutants, including particulate matter (PM₂.₅ and PM₁₀), carbon monoxide (CO), nitrogen dioxide (NO₂), sulphur dioxide (SO₂), and ozone (O₃) were measured, along with the Air Quality Index (AQI) and non-carcinogenic health risk indicators. The results revealed high particulate matter levels, with PM₂.₅ ranging from 38.2 ± 6.3 to 72.1 ± 10.4 µg/m³ and PM₁₀ from 70.8 ± 11.5 to 136.2 ± 17.8 µg/m³, surpassing recommended standards. Carbon monoxide levels varied between 2.4 ± 0.6 and 6.8 ± 1.2 ppm, while NO₂ and SO₂ concentrations ranged from 0.028 ± 0.009 to 0.065 ± 0.011 ppm and 0.012 ± 0.004 to 0.034 ± 0.007 ppm, respectively. AQI values ranged from 94 in semi-urban areas to 182 in traffic-heavy locations, indicating moderate to unhealthy air quality. Hazard quotient values for PM₂.₅ (2.14) and PM₁₀ (1.89) indicated potential non-carcinogenic health risks from prolonged exposure. The findings underscore the impact of industrial emissions, gas flaring, vehicular activity, and urban energy needs on air quality in Port Harcourt. Ongoing environmental monitoring, stricter regulation enforcement, cleaner energy adoption, and better urban environmental management are recommended to reduce pollution and safeguard public health in the Niger Delta region.
