Particulate matters deposition in the human respiratory system: A health risk assessment at a technical university
This study quantified Particulate Matter (PM) deposition and its clearance in the Human Respiratory Tract (HRT) at different microenvironments of a university. The university is located adjacent to the National Highway (NH 334) and main bus stop of the city, thus highly affected by PM pollution.
The deposition calculations were performed using a widely accepted MPPD 3.04 model. Three seasons (summer, winter and monsoon), seven microenvironments (including three Lecture Hall Complexes (LHCs), a library, two laboratories and outdoor), and different activity patterns associated with each microenvironment were considered.
The deposited mass of coarse fraction (PM2.5-10) in different HRT regions follows the order: pulmonary (0.5%)<tracheobronchial (2%)<head (or extrathoracic region) (97.5%). In the case of lobar region, because of the larger volume of lower lobes, they received higher deposition (53%) than the middle (8%) and upper lobes (39%). Further, the sitting activity level was found to be most critical for lobar deposition. The total deposited mass in the HRT was maximum outdoors and minimum at the library. The difference in winter and monsoon deposition was 100% for PM2.5-10, 75% for PM1-2.5 and 126% for PM1. The clearance rate of PM1 is such that 1.5 % of particles in the tracheobronchial and 64% in the pulmonary region remained even after six months.
The results implied that physical activity levels, mode of inhalation and particle size significantly influence regional deposition. For instance, heavy exercise causes greater deposition in the head region, whereas sitting activity contributes to higher pulmonary and tracheobronchial deposition.
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