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 μg/m³ (indoor) and 101?±?42.8 μg/m³ (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?×?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.