Assessment of Health Risks Associated With Air Pollution in Onitsha, Anambra State, Nigeria

This study assessed the air quality around Onitsha metropolis by monitoring the concentration of selected air pollutants namely; particulate matter (PM2.5, PM10) nitrogen dioxide (NO2), sulphur dioxide (SO2), hydrogen sulphide (H2S), ammonia (NH3), carbon monoxide (CO), methane (CH4), volatile organic carbon (VOCs) and ozone (O3); as well as different meteorological parameters, including atmospheric temperature, relative humidity, wind speed, wind direction and noise. Seven locations were studied between the months of July and February using portable hand-held air quality monitoring devices. Sampling was carried out daily for one week between 8am-5pm in each of the selected location. The concentrations of all the measured air pollutants were found to be higher during the dry season than at rainy season. The mean concentration of pollutants during the dry season are PM2.5 170.711 ±11.67 g/m3, PM10 180.28 ± 111.60 g/m3, CO 10.3 ±18.30 ppm, NO2 0.357 ±0.336 ppm, VOCs 2.4286 ±1.8830 ppm, CH4 1.1643±1.2378 ppm, H2S 0.0286 ±0.03485 ppm; and during the rainy season PM2.5 38.914 ±27.81 g/m3, PM10 62.557 ± 47.08 g/m3, CO 3.786 ±2.76 ppm, SO2 0.2500 ±0.353, NO2 0.671 ±1.578 ppm, VOCs 0.2900 ±0.2115 ppm, CH4 0.01 ±0.00 ppm, H2S 0.00 ±0.00 and 03 0.00 ±0.00 ppm. Air quality was determined using the WHO air quality index (AQI) technique. The overall air quality of Onitsha metropolis was found to be hazardous during the dry season but unhealthy for sensitive groups during the rainy season. The prevailing atmospheric condition per season (wind speed, relative humidity, temperature and wind direction) in the locations assessed contributed significantly to the dispersion and transportation of the pollutants. This study therefore recommends continuous monitoring of air pollution levels in Onitsha metropolis as well as other urban cities and appropriate environmental safety measures to reduce the risk posed by air pollution.