Estimation of the Inhaled Dose of Airborne Pollutants during Commuting: Case Study and Application for the General Population

Abstract

During rush hours, commuters are exposed to high concentrations and peaks of traffic-related air pollutants. The aims of this study were therefore to extend the inhaled dose estimation outcomes from a previous work investigating the inhaled dose of a typical commuter in the city of Milan, Italy, and to extend these results to a wider population. The estimation of the dose of pollutants inhaled by commuters and deposited within the respiratory tract could be useful to help commuters in choosing the modes of transport with the lowest exposure and to increase their awareness regarding this topic. In addition, these results could provide useful information to policy makers, for the creation/improvement of a mobility that takes these results into account. The principal result outcomes from the first part of the project (case study on a typical commuter in the city of Milan) show that during the winter period, the maximum deposited mass values were estimated in the "Other" environments and in "Underground". During the summer period, the maximum values were estimated in the "Other" and "Walking (high-traffic conditions)" environments. For both summer and winter, the lowest values were estimated in the "Car" and "Walking (low-traffic conditions)" environments. Regarding the second part of the study (the extension of the results to the general population of commuters in the city of Milan), the main results show that the period of permanence in a given micro-environment (ME) has an important influence on the inhaled dose, as well as the pulmonary ventilation rate. In addition to these results, it is of primary importance to report how the inhaled dose of pollutants can be strongly influenced by the time spent in a particular environment, as well as the subject's pulmonary ventilation rate and pollutant exposure levels. For these reasons, the evaluation of these parameters (pulmonary ventilation rate and permanence time, in addition to the exposure concentration levels) for estimating the inhaled dose is of particular relevance.

Keywords: PM; active transportation; commuting; micro-environment; pollution; pulmonary ventilation rate; risk assessment; travel mode.

Figure 1

Lombardy region (left) and the complete route traveled by the subject from Villa Guardia (45°47′ N 9°01′ E) to the city center of Milan (45°27′ N 9°11′ E) (right).

Figure 2

PM deposited mass (µg) in the respiratory tract (H: head; TB: tracheobronchial; P: pulmonary; total: H + TB + P). Black: PM₁; Blue: PM_2.5; Green: PM₄; Yellow: PM₁₀.

Figure 3

Proportions of subjects who move through different transport MEs within the city of Milan. In the figure, the data are divided by gender (female or male) and by permanence periods ((a): 15 min, (b): 30 min, (c): 60 min, (d): 90 min).