Assessment of concentration of the potentially toxic elements and associated human health risk from particulate matter exposure along road intersections in Ibadan, southwestern Nigeria

Abstract

The harmful health effect of suspended particulate matter (PM10) is mostly associated with its mass concentrations and chemical compositions. Therefore, this study focuses on the determination of the particulate matter (PM10) concentrations and their potentially toxic elements (PTEs) composition from different road networks in Ibadan southwestern, Nigeria. In addition, human health risk assessment was estimated from the PTE data. The PM10 samples were collected from different road networks such as national highway roads (NHR), inner-city major roads (ICR), and remote roads (RRD) in Ibadan, Nigeria. The sampling was carried out with a high-volume air sampler (model #15000 manufactured by Science Resource, Walboro, USA) with a PM10 cut-off on a Whatman cellulose filter during the harmattan period. The PM10 concentrations and PTEs compositions (Al, Ba, Cd, Cu, Fe, La, Mo, Mn, Ni, Pb, V, and Zn) were determined by gravimetry and inductively coupled plasma-optical emission spectrometry (ICP-OES) methods (VISTA-MPX manufactured by Varian Incorporation), respectively. The PM10 concentrations in all three road networks were more than 3 folds higher than World Health Organization (WHO), United State Environmental Protection Agency (USEPA), and United Kingdom Environmental Protection Agency (UKEPA) standards (50 µg/m3) for 24 h. The maximum average contents of Ba, Cd, Cu, La, Mn, Pb, and V, were observed at NHR, while that of Al, Fe, Mo, and Zn, were found at ICR. The principal component analysis (PCA) showed that PC1 (Ba, Cd, Cu, La, Mo, Pb, and V) and PC4 (Zn) were characterised by elemental markers of both exhaust emission and non-exhaust emissions, while PC2 (Mn) and PC3 (Al, Fe) were characterised by crustal elements. The Enrichment factor (EF) analysis classified all the PTEs as moderately to very highly enriched, especially in NHR and ICR, except Al, Fe, and to some extent Mn. Both the maximum and average hazard quotient (HQ) levels of Cd, Cu, Mn, Pb, and Zn were < 1, which was within the permissible level. Also, the carcinogenic risk (CR) was also within the permissible limit.