How safe are the classrooms in nursery and primary schools?: The Nigerian study

Environmental pollution caused by potentially toxic elements (PTE) from various anthropogenic sources has become a global concern. An estimated 7 million premature deaths occur globally each year owing to ambient and indoor air pollution. This study assessed the concentration of PTE, level of contamination and human health risks of dust samples collected from classrooms in Abeokuta, South-Western Nigeria. Samples were collected from windowsills, chair, tables, and corners of the classrooms. Digestions of the samples were performed at College of Environmental Resource Management, Federal University of Agriculture, Abeokuta, Ogun state, Nigeria. PTE analyses revealed that the concentration of PTE (Cd, Cr, Cu, Fe, Ni, Pb, and Zn) measured were all within acceptable safe limit levels suggesting they were not contaminated. Pollution assessment tools employed (Enrichment factor and Contamination factor) revealed a descending order pattern of Cd > Pb > Zn > Cu > Cr > Ni > Fe. Source apportionment studies showed Cd, Cu, and Pb may have originated from anthropogenic sources, Cr and Ni from natural sources while Fe and Zn appeared to have emanated from mixed sources (natural and anthropogenic). The hazard quotient and hazard index values were lower than the safe limit of 1 suggesting no significant non-cancer effect to children and adult populations. Ingestion was the major exposure route for PTE followed by dermal contact and inhalation in that order. Cancer risk estimations were within the permissible limit of 10(-6) to 10(-4) and therefore suggests no carcinogenic effects, except for Cr. Furthermore, Cr was the predominant contributor to cancer effects and accounted for 96% for both children and adult populations. Regular monitoring of dust particulates is necessary to keep PTE contents low in the ambient air and consequently reduces human exposure to health risks.