The PM10 compositions, sources and health risks assessment in mechanically ventilated office buildings in an urban environment

Office buildings can be considered a second home for working people and so the contribution of pollutants in this indoor environment to a person's overall exposure is significant. The aims of this study were to examine the composition of PM10 and the sources influencing the indoor and outdoor office environments. The PM10 sampling was performed using a mini-vol portable sampler at two sampling sites from May to August 2014 for daily 24 h sampling. The concentrations of ionic species (F-, Cl-, NO3 (-), SO4 (2-)) were analysed using ion chromatography while the concentration of major elements (Mg, Ca, K, Na) and trace elements (Mn, Ni, Fe, Cu, Zn, Pb, Cr, Cd, Al) were determined by inductively couple plasma-mass spectrometry (ICP-MS). The concentration of NH4 (+) was determined using the indophenol blue method. The results showed that the average concentrations of PM10 were 61.3 +/- 27.0 mu g/m(3) (indoor) and 101 +/- 42.8 mu g/m(3) (outdoor) with an indoor/outdoor ratio value of < 1. The dominant components in PM10 for both the indoor and outdoor environments were NO3 (-), SO4 (2-), Na, Fe, Al and Zn. Source apportionment analysis of the PM10 composition identified three sources of PM10 in the indoor and outdoor environments. The major source for indoor PM10 was Earth's crust elements (95 %) followed by oil burning and human activities (4 %) and motor vehicles (1 %). The major source for outdoor PM10 was the Earth's crust and motor exhaust emissions (80 %) with contributions of other sources such as oil burning and human activities (18 %) and motor vehicles (2 %). The potential health risks for trace elements in PM10, via inhalation exposure to the indoor occupants, show that the total hazard quotient (HQ) value was slightly higher than acceptable limits (1.0). The total excess life time carcinogenic risk (ELCR) value for both sampling stations was higher than the acceptable limit (1.0 x E-6), suggesting a high exposure to carcinogenic risk. This study suggests there is a high contribution of outdoor sources to the indoor office environment where PM10 can significantly affect the indoor air quality and occupant health.