Application of multiple-path particle dosimetry model for quantifying age specified deposition of particulate matter in human airway

Abstract

Particulate matter (PM) is crucial among six criteria air pollutants, and it is frequently associated with human morbidity and mortality. According to the aerodynamic diameter, PM is classified as coarse (PM₁₀) and fine (PM_2.5). PM with these smaller sizes can easily enter and get deposited in the human airways. This deposited PM fraction commences the development of respiratory diseases such as asthma, chronic obstructive pulmonary disease, and even cancer. Thus, the quantification of PM deposition and its clearance in the human airway are essential for evaluating health risks. This study aims to investigate the size-segregated PM (PM₁₀, PM_2.5, and PM₁) deposition in human lungs. Size-segregated PM is collected using the Grimm portable environmental dust monitor during winter season near an arterial road located in Chennai city of Tamil Nadu state, India. Multiple-Path Particle Dosimetry (MPPD) Model version 3.04 is utilized for quantifying PM deposition. In MPPD, airway structures of infants (3 and 28 months), children (3, 8, 9 and 14 years) and adults (18 and 21 years) are considered for the study. The values of PM concentration, body orientation, breathing scenario, tidal volume, pause fraction, inspiration fraction, and breathing frequency are specified in the MPPD for quantifying PM depositions. Results showed that 8-year children and 28 months infant groups are recorded with maximum and minimum size-segregated PM deposition respectively. The coarse particles (PM₁₀) are primarily deposited in the head (55-95%) and tracheobronchial (3-44%) regions whereas fine particles (PM_2.5 and PM₁) depositions are observed maximum in the head (36-63%) and pulmonary (28.2-52.7%) regions. Except for the adult age group, PM_2.5 has the maximum deposition percentage in tracheobronchial and pulmonary regions. In the case of lobar depositions, lower lobes receive maximum deposition (66.4%) than the upper (27.2%) and middle lobes (6.4%). PM_2.5 dominated the deposition in all five lobes of infant, children, and adults. The clearance rate of deposited PM is high in the tracheobronchial region whereas it is low in the pulmonary region. This study also concludes that PM_2.5 is the important size fraction in lung deposition. Further, the study results can be used for human health risk assessments such as oxidative potential and toxicity of deposited PM.

Keywords: Health risk assessments; Lobar deposition; MPPD Model; PM Clearance; Regional deposition; Size-segregated PM.