Characteristics and Health Risk Assessment

22 In China, the exposure of children to particulate toxics, like organics, has been poorly 23 investigated mainly due to the technical challenges in sampling and analysis. This 24 article reports indoor and outdoor concentrations of PM2.5-bound polycyclic aromatic 25 hydrocarbons (PAHs), oxygenated-PAHs (OPAHs) and phthalate esters (PAEs) 26 monitored for 13 days in May 2012 in two classrooms, A and B, of a middle school at 27 Xi’an, China. Outdoors, the average PM2.5 mass was 96.9 μg/m, while indoor 28 concentrations ranged between 154.7 μg/m (A) and 120.2 μg/m (B). Total PAEs, 29 dominated by Bis(2-ethylhexyl)phthalate (DEHP) and di-n-butyl phthalate (DBP), 30 were found at much higher concentrations than PAHs and OPAHs, and their outdoor 31 versus indoor distribution followed that of PM2.5, ranging from 622.0 ng/m outdoors, 32 to 808.6 (A) and 864.7 ng/m (B) indoors. Concentrations of total PAHs were about 33 50 ng/m outdoors and indoors, while OPAHs were observed at concentrations of 17.7 34 outdoors and 15.9 (A) and 19.8 ng/m (B) indoors. High molecular weight PAHs (i.e., 35 4-ring, 5-ring and 6-ring) generally accounted for about 80%. Variations of PAHs 36 levels indoors were closely associated with the ventilation and the occupancy rate of 37 the classrooms. Activities on the playground also influenced the indoor organic 38 pollutant concentrations. Intense PAEs sources were evidenced, but outdoor sources 39 also influenced the I/O ratios. Both the PAHs and PAEs inhalation risk estimations 40 demonstrated that there is a non-negligible potential cancer risk for children in their 41 school environment. 42 43