PM_2.5-bound polycyclic aromatic hydrocarbons (PAHs), oxygenated-pahs and phthalate esters (PAEs) inside and outside middle school classrooms in Xi’an, China: Concentration, characteristics and health risk assessment

In China, the exposure of children to particulate toxics, like organics, has been poorly investigated mainly due to the technical challenges in sampling and analysis. This article reports indoor and outdoor concentrations of PM_2.5-bound polycyclic aromatic hydrocarbons (PAHs), oxygenated-PAHs (OPAHs) and phthalate esters (PAEs) monitored for 13 days in May 2012 in two classrooms, A and B, of a middle school at Xi’an, China. Outdoors, the average PM_2.5 mass was 96.9 µg m^–3, while indoor concentrations ranged between 154.7 µg m^–3 (A) and 120.2 µg m^–3 (B). Total PAEs, dominated by bis(2-ethylhexyl)phthalate (DEHP) and di-n-butyl phthalate (DBP), were found at much higher concentrations than PAHs and OPAHs, and their outdoor versus indoor distribution followed that of PM_2.5, ranging from 622.0 ng m^–3 outdoors, to 808.6 (A) and 864.7 ng m^–3 (B) indoors. Concentrations of total PAHs were about 50 ng m^–3 outdoors and indoors, while OPAHs were observed at concentrations of 17.7 outdoors and 15.9 (A) and 19.8 ng m^–3 (B) indoors. High molecular weight PAHs (i.e., 4-ring, 5-ring and 6-ring) generally accounted for about 80%. Variations of PAHs levels indoors were closely associated with the ventilation and the occupancy rate of the classrooms. Activities on the playground also influenced the indoor organic pollutant concentrations. Intense PAEs sources were evidenced, but outdoor sources also influenced the I/O ratios. Both the PAHs and PAEs inhalation risk estimations demonstrated that there is a non-negligible potential cancer risk for children in their school environment.