Micromorphology of size-segregated aerosols and their airway deposition in public transport commuters

AbstractCommuters ’ exposure to size-segregated fine particulates in four public transport microenvironments was assessed in the Kolkata megacity of India. Personal exposure to PM2.5 and PM1 varied from 130.8& 112.1 μg m−3 in air-conditioned (AC) buses, followed by 158.5 μg m−3 & 134.3 μg m−3 in non-AC buses, 187.1 μg m−3 & 150.8 μg m−3 in non-AC cars, to 242.2 μg m−3 & 199.6 μg m−3 in 3-wheeler auto rickshaws, respectively. The exposure ratio for PM1/PM2.5 was comparable in all transport modes (0.64 to 0.94, 0.83 ± 0.07). The micromorphology of fine particulates, studied by scanning electron microscopy-energy-dispersive X-ray spectrometry, revealed several morphological features in both inorganic and carbonaceous particulates with Al, Si, Ca, K, Fe, and S impregnations. Soot particles were predominantly pre sent in PM<  0.25, and its semi-aggregated net-like structure trapped fine and ultrafine particles. The possible formation of carbonaceous aerosols from inorganic seeds via the nucleation pathway was also captured. The estimated deposition rate in the human respiratory system translated into a total PM2.5 respiratory deposition rate (RDR) of 25.5 ± 8.9 μg h−1 in the respiratory tract was about 26% of the entire inhalation exposure to PM2.5. The average RDR of PM2.5 –1.0 and PM1.0 –0.5 was 11.7 ± 5.9 μg h−1 and 4.5 ± 2.3 μg h−1 that may get preferentially deposited in the head airways of the human respiratory ...
Source: Air Quality, Atmosphere and Health - Category: Environmental Health Source Type: research