Compositions, source apportionment and health risks assessment of fine particulate matter in naturally-ventilated schools

Abstract

Good indoor air quality in school environment is crucial for teaching and learning processes, as well as student development. This study aims to identify the composition of PM2.5 and the main sources of it which influence the indoor and outdoor school environment. The PM2.5 sampling was conducted using a portable low volume air sampler and took place at three different primary schools. The chemical composition of PM2.5 is comprised of water-soluble inorganic ions (WSII) and potentially toxic trace metals. WSII (Cl−, NO3−, SO42−, Na+, NH4+, K+, Mg2+, Ca2+) were analysed using ion chromatography (IC) and trace metals concentrations (Al, Fe, Zn, Cr, Cu, Mn, Pb, Ni, As, Co, Cd) using inductively coupled plasma-mass spectrometry (ICP-MS). The results showed that the highest average for PM2.5 concentrations in an indoor classroom was recorded at the school located in the industrial area (23.5 μg/m3) followed by urban (18.6 μg/m3) and suburban (9.58 μg/m3). The indoor to outdoor (I/O) ratio values for PM2.5 concentrations were slightly above one, indicating that open doors and windows highly affected indoor PM2.5 concentrations. Source apportionment analysis indicated that the sources of both indoor and outdoor PM2.5 were mixed of natural (crustal, mineral dust and sea salt) and anthropogenic (vehicle, industrial and biomass burning). The hazard quotient (HQ) value was lower than the acceptable limits. The excess lifetime cancer risk (ELCR) value for all three stations, however, was found to be slightly higher than the acceptable level (1.0E-06) for Cr and Ni.