Concentrations, source identification and human health risk of heavy metals in the road dust collected from busy junctions in Osogbo Southwest, Nigeria

Abstract

The study determined the concentrations of heavy metals in the road dust samples collected in some selected busy traffic junction in Osogbo, southwest, Nigeria. This was to identifying the sources of heavy as well as the evaluating the associated human health risks. The concentrations of Pb, Cu, Cd, Ni, Co, Cr, Zn, Mn, and Fe were determined by employing Atomic Absorption Spectrophotometer. The sources were identified using non-negative constraint Positive Matrix Factorization receptor model and the health implication were assessed using risk indices consist of average daily doses via: dermal, inhalation and ingestion; Hazard Quotient (HQ); hazard index (HI); and lifetime average daily dose (LADD). The total average concentrations of Fe, Mn, Cu, Zn, Cr, Cd, Pb, Ni, and Co were 5030.0, 80.52, 15.14, 49.0, 6.81, 2.80, 1.77, 1.31, 1.98 µg/g, respectively and they were few order higher than their values in the local background site. The inhalation appeared to be the major exposure pathway of heavy metals in the road dust to the adults and children followed by dermal contact and ingestion. The sequences of HQ values are Cd < Ni < Zn < C u < Pb < Cr and Cu < Cd < Pb < Cr < Ni < Zn for adults and children. The HI values for the adults and children are 0.2 and 0.5, showing that any of Cu, Zn, Cr, Cd, Pb and Ni will unlikely cause negative human health effect through multiple exposure routes. The cumulative value of LADD for Cu, Zn, Cr, Cd, Pb and Ni is 1.70 x 10−5 which falls within the acceptable limit value of 10−4 to 10−6. The four main sources resolved by PMF and their relative contributions were vehicular components wear (36 %), fuel and lubricating oil (30 %), tyre particles wear (23 %), and battery corrosion and leakage (11 %).

Keywords

• traffic
• road dust
• exposure
• health risks