Assessing the Impact of Industrial Emissions on Local Air Quality in Onitsha, Anambra State

Onitsha in Anambra State hosts one of West Africa's largest commercial markets and several industrial establishments whose atmospheric emissions have raised persistent air quality concerns. This study assesses the impact of industrial and commercial emissions on local air quality in Onitsha, combining ambient particulate matter (PM2.5 and PM10) measurements with meteorological observations. Field measurements of PM2.5 and PM10 concentrations were conducted at 10 selected sampling points across industrial, commercial, and residential land use zones over a six-month monitoring campaign spanning both dry and wet seasons of 2023. Meteorological data including wind speed, wind direction, and mixing layer height from NiMet Enugu Airport station were used to contextualize dispersion conditions. Results indicate that mean PM2.5 concentrations at industrial perimeter sites exceed the WHO 24-hour guideline of 15 micrograms per cubic metre by up to 4.8 times during the dry season when low wind speeds and stable atmospheric conditions limit pollutant dispersion. Residential zones downwind of the main industrial cluster consistently record higher concentrations than upwind neighborhoods, confirming directional transport of pollutants. The study identifies generator exhaust, open burning, and vehicular emissions as compounding pollution sources. Recommendations include adoption of ambient air quality monitoring regulations by Anambra State Environmental Protection Agency and installation of permanent monitoring stations in Onitsha. Keywords: air quality, particulate matter, industrial emissions, Onitsha, dispersion.