Spatial, seasonal and particle size dependent variations of PAH contamination in indoor dust and the corresponding human health risk.

To investigate the particle size distribution, spatial variation, and corresponding health risks of polycyclic aromatic hydrocarbons (PAHs) in indoor environments, composite settled dust samples were collected from four types of microenvironments (offices, hotels, dormitories and kindergartens) in Beijing, and each pooled dust sample was homogenized and fractionated into 9 fractions (F1 (900-2000 μm), F2 (500-900 μm), F3 (400-500 μm), F4 (300-400 μm), F5 (200-300 μm), F6 (100-200 μm), F7 (74-100 μm), F8 (50-74 μm), and F9 (<50 μm)). The total concentrations of 15 PAHs varied from 388 ng g-1 (kindergarten dust, F1) to 8140 ng g-1 (hotel dust, F7) in the 31 size-segregated samples. Particle size distribution patterns of PAHs were found to vary for the different types of dust samples. The seasonality of PAH contamination in indoor dust was discussed within 36 samples collected weekly and biweekly from two offices of one building in Beijing. Generally, the seasonal trends of PAHs in dust from these two offices were consistent, showing that PAH levels in cold seasons were higher than those in warm seasons. Diagnostic ratios and principal component analysis (PCA) indicated the important contribution of fuel combustion to PAHs in the indoor dust samples. The estimated incremental lifetime cancer risk (ILCR) values ranged from 10-6 to 10-5 for all relevant populations corresponding to the four types of microenvironments.