Environmental assessment of potentially toxic metals in settled indoor dust of primary school classrooms in suburban communities of Southwestern Nigeria

Abstract

Emissions of particle-phase species from on-road motor vehicles are known to be a major contributor to the atmospheric particulate matter burden, which, upon deposition, leads to indoor dust accumulation and acts as a reservoir for particle-bound metals. This study assessed concentrations, pollution status, ecological risk, and sources of potentially toxic metals (PTMs) in classroom dust from pre-/primary schools in areas with diverse traffic densities and evaluated pupils’ exposure to environmental toxins. Thirty-six composite dust samples were collected from classrooms of pre-/primary schools in suburban communities in two States of Southwestern Nigeria. The samples were analysed for PTMs using an Energy-Dispersive X-ray Fluorescence (EDXRF) Spectrophotometer. The mean metal concentrations followed the order Fe > Al > Co > Zn > Mn > Pb > Cu > Ni > As > Ag > V > Cr > Cd, with significantly higher levels generally observed at high-traffic sites ( p < 0.05). Pollution indices, including contamination factor, geo-accumulation index, pollution load index, Nemerow pollution index, and potential ecological risk index, indicated varying degrees of contamination and ecological risk across the study locations, with As and Cd contributing substantially to elevated contamination factors and ecological risk at several sites. Ni, Cu, Zn, Pb, and As were the dominant contributors to pollution, with As and Pb presenting extreme pollution and ecological risk at several sites. Principal component analysis (PCA) and positive matrix factorisation (PMF) identified vehicular emissions, mechanical wear, industrial activities, and resuspended soil as the major sources of metal contamination. The results of the study highlight the need for continued environmental monitoring and further studies incorporating human health risk assessments to evaluate potential impacts on children and school staff.