Deposition Modeling of Airborne Particulate Matter on Human Respiratory Tract During Winter Seasons in Arid-Urban Environment

This study aimed to predict winter season street-level ambient particulate matter (PM) depositions within human airways using Multiple-Path Particle Dosimetry (MPPD) model. The PM exposure concentrations in the downtown street of As-Seeb, Oman were measured continuously over 20 days (31 October–9 December 2018) using a mobile ambient air quality monitoring instrument equipped with sensors. The MPPD model together with the associated default respiratory parameters was implemented to quantify the total, head, tracheobronchial (TB), and pulmonary (PL) regional PM depositions in airways among children (3, 8, and 14 years old) and adults (18 and 21 years old) groups. The street-level PM exposure concentration (µg/m³) levels for PM₁₀ (avg 69.64; IQR 15.1), PM_2.5 (avg 13.76; IQR 1.36) and PM₁ (avg 3.67; IQR 0.52) was obtained during the winter season. The average 24-H PM_2.5 (14 µg/m3) concentration was about 60, 50 and 44% lower when compared to US National Ambient Air Quality Standards (NAAQS), Canadian Ambient Air Quality Standard (CAAQS), and WHO daily ceilings of 35, 28 and 25 µg/m³, respectively. Across all the age groups, the total airways deposition was found to be very high in PM₁₀ (92–99%), followed by PM_2.5 (61–76%) and PM₁ (33–49%) being the least. Similarly, the average deposition of PM₁₀ in the head region (76%) was observed to be more than 4–15 times higher than TB (16%) and PL (4%) for all ages. Children recorded higher PM_2.5 depositions in the TB (53–59%) region compared to adults (TB 47–51%). The PM₁₀ lobar deposition of 8-year-old children is more than 7 times higher compared to 21-year-old adults due to their lower breathing heights and higher breathing rates. In general, PM clearance was very high in TB and poor in the alveolar region.