Levels of Heavy Metals in Traffic-Related Particulate Matter along a Major Motorway in Ibadan North-East Local Government Area, Nigeria (20m Lecture)

 Background: Traffic-related particulate matter contributes extensively to ambient air pollution especially in urban centres. Hence, Populations found along major urban motorways are at higher risk of various health effects. This study was therefore designed to determine levels of heavy metals in the air along IdiApe-Iwo road motorway in Ibadan North-East Local Government Area.

Methods: Descriptive study design involving air sampling and particulate analysis for selected heavy metals was used. At all five sampling locations, levels of particulate matter (PM10) at intervals of 10, 20 and 30 metres away from the motorway were measured using calibrated fine particulate matter sampler. Measurements were done in the morning (7-10am) and afternoon (1-4pm) for 10 weeks. Filter papers obtained from the sampler from SL were digested and analysed for Lead (Pb), Iron (Fe), Copper (Cu), Cadmium (Cd), Zinc (Zn), Chromium (Cr) and Nickel (Ni) using atomic absorption spectrophotometry according to standard methods. Data were analysed using descriptive statistics, ANOVA and Pearson correlation test at p <0.05.

Results: Daily PM10 level at each sampling location were AB (100.5 ± 36.3µg/m3), IA (96.3 ± 42.1µg/m3), BA (84.6 ± 41.7µg/m3), AL (110.1 ± 48.4µg/m3), and HJ (121.6 ± 59.8µg/m3) was 4-6times above the PM10 guideline limit of 20µg/m3. The mean levels of heavy metals were Pb (161.1 ± 108.3mg/m3), Fe (2.54 ± 1.09mg/m3), Cu (0.91 ± 0.31mg/m3), Cd (52.5 ± 30.7mg/m3), Zn (0.52 ± 0.39mg/m3), and Cr (0.19 ± 0.03mg /m3). Spatial variations in PM10 and heavy metal concentrations were found to reduce with distance further away from traffic by 23.5% and 18.7% respectively.

Conclusion: Levels of heavy metals at all sampling locations along Idi-Ape-Iwo road motorway exceeded permissible guideline limits for urban centres. Periodic air monitoring of motorways should be instituted. This should be targeted at reducing traffic-related particulate matter concentrations on our motorways especially from exhaust emissions.