Assessment of Gaseous Air Pollutants around Selected Open Dumpsites in Ilorin, Kwara State, Nigeria

Abstract

Open dumping remains the dominant method of municipal solid waste disposal across many Nigerian cities, yet routine monitoring of the gaseous pollutants these sites release is still uncommon. This study assessed eight gaseous pollutants, carbon monoxide, carbon dioxide, nitrogen dioxide, sulphur dioxide, ammonia, hydrogen sulphide, methane, and volatile organic compounds, around three open dumpsites in Ilorin metropolis, Kwara State, Nigeria, namely Gbagede, Sokoto/Ayekale, and Sango. Readings were taken weekly, morning and evening, across a dry and a wet season, and the data were compared among sites using the Kruskal-Wallis test with Bonferroni corrected comparisons, then checked against air quality and occupational reference values using Wilcoxon signed-rank and chi-square tests. Volatile organic compounds recorded the highest mean concentration (2872.66 ± 3455.55 ppm), followed by methane (81.47 ± 49.20 ppm), while nitrogen dioxide returned the lowest mean (0.19 ± 0.17 ppm). Concentrations differed significantly among the three dumpsites for seven of the eight pollutants, with Sokoto/Ayekale generally recording the highest values and Gbagede the lowest. Against World Health Organization guideline values, nitrogen dioxide exceeded the 24-hour limit in 80.05% of readings and sulphur dioxide in 75.26%, carbon monoxide exceeded its limit in 21.46% of readings, and hydrogen sulphide exceeded its occupational reference in only 1.92% of readings. These findings show that residents and workers around the dumpsites, especially Sokoto/Ayekale, face regular exposure to pollutant levels above recognized health-based guidelines, pointing to the need for stronger waste management and routine air quality surveillance in Ilorin.