Deposition of aerosol particles from a subway microenvironment in the human respiratory tract

Abstract

a b s t r a c tConventional subway systems are characterized by high particulate matter (PM) concentrations. To relate PM exposure to adverse health effects it is important to determine the dose of the inhaled particles in the human respiratory tract (HRT). Therefore, the total and regional doses of particles for a healthy adult male using the dosimetry model ExDoM in the subway system were estimated. The overall dose was determined using the average exposure PM 2.5 concentrations obtained from an extensive campaign in the Barcelona subway system, including measurements on the platforms and inside the trains. Despite the lower PM 2.5 concentrations inside the trains with respect to those on station platforms, the highest dose was observed inside the trains due to longer exposure time, evidencing the importance of the exposure period in the estimation of the particle dose. Overall, during a subway commuting travel, roughly 80% of the inhaled mass of subway PM 2.5 was deposited in the HRT. The highest amount of the inhaled particles was deposited in the extrathoracic region (68%), whereas the deposition was much smaller in the tracheobronchial tree (4%) and alveolar-interstitial region (10%). Individual's daily exposure to PM 2.5 and dose were estimated, considering a typical time-activity pattern of an adult male who lives in Barcelona and commutes by subway. While a subject typically spends approx. 3% of the day in the subway system, this microenvironment may account for up to 47% of the total PM 2.5 daily dose. These results might be similarly high for other commuting modes due to the reported high PM exposure levels. The dose is mainly dependent on the particle size and exposure concentrations.

Prediction of Aerosol Deposition in the Human Respiratory Tract via Computational Models: A Review with Recent Updates

“…Additionally, the PM deposited in the human respiratory tract depends on different factors such as PM exposure concentration, PM physicochemical characteristics, exposure duration, and exposed-subject characteristics (age, gender, state of health, lung morphology, and breathing parameters) [12].…”

“…Because commuters face different mobile emission sources, high PM exposure levels have been found for all transportation modes (car, bus, subway, motorbike, cycling, and pedestrian). In the case of subway systems, PM concentration levels are higher than in the outdoor ambient air [12]. The movement of trains, passengers, and also outside air flows through ventilation systems can contribute to the generation of PM [42].…”

“…The movement of trains, passengers, and also outside air flows through ventilation systems can contribute to the generation of PM [42]. Martin et al (2015) also used the ExDoM to predict PM deposition in the human respiratory tract, explicitly using the published PM 2.5 concentrations of the Barcelona metro system [12]. They found that, although the PM 2.5 level inside the train was lower than those on the station platforms, the highest dose was found inside the trains due to the longer duration of exposure.…”

“…However, due to experimental limitations, the regional dose in the respiratory system is hard to measure experimentally but can be predicted by the application of different mathematical models. Suitable mathematical models are those that show a reasonable correlation between results obtained from modeling and empirical measurements [12]. Computational models generally consist of three elements: (1) a mathematical formulation that describes the relevant physical and chemical processes, (2) the setting of specific initial and boundary conditions, and (3) the solving of equations for the specified geometry.…”

Numerical assessment of airflow and inhaled particles attributes in obstructed pulmonary system

“…The importance of individual exposure to aerosol particles from a subway microenvironment in the human respiratory tract, along with the dose assessment, in order to provide information for the protection of public health has been described by [23]. As an example, deposition of inhaled particles within airway generations of an adult woman was determined by a stochastic lung deposition model for sleeping, sitting, light and heavy exercise breathing conditions [24].…”