Spatial Distribution, Pollution Index, Receptor Modelling and Health Risk Assessment of Metals in Road Dust from Lagos Metropolis, Southwestern Nigeria

Abstract This study assessed the spatial distribution, pollution index, receptor modelling and health risk of metals in road dust samples from Lagos metropolis, Southwestern Nigeria. Paved and unpaved road dust samples were collected from twenty locations for three consecutive months. Seventy two samples (including control soils) were collected and analysed for metals using inductively coupled plasma - optical emission spectrophotometry. Dust and control soil data were manipulated for descriptive and inferential statistics. Road dusts and control soil revealed high concentrations of Ca (758-2509 mg kg−1), Mg (693-1461 mg kg−1), Fe (583-2493 mg kg−1), Ti (189-785 mg kg−1) and Zn (42-1255 mg kg−1). The geospatial map identified pollution hotspots for Ca, Cd, Cr, Cu, Fe, Mg and Mn at the mainland parts of Lagos state. The receptor models (positive matrix factorization and principal component analysis) identified emission sources from steel industry, traffic emission, crustal matter and combustion processes. The pollution assessment (pollution index, ecological risk index, Nemerov integrated pollution index and enrichment factor) indicated high contamination levels for As, Cd, Pb and Zn in dust/soil. The health risk of metals evaluated for non-carcinogenic [average daily dose (ADD), hazard quotient (HQ), hazard index (HI)] and cancer risk (CR) revealed the HQs greater than 1.0 for As and Ca, an indication of adverse health effects. The CRs of As, Cr, Cd and Ni were higher than the acceptable limit of 1.0 × 10−4, suggesting probable development of cancer.