Comparative analysis of particle exposure in commuters: Evaluating different modes of transportation in Tehran

Abstract

Daily commuting significantly contributes to the overall exposure to particulate matter (PM) in urban areas, underscoring the need to understand the factors influencing PM exposure. This study assessed personal exposure levels and inhalation doses of PM_2.5, and PM₁₀ across various transportation modes in Tehran, Iran. The study included buses, open-window taxis, subways, walking, and cycling for over 125 trips. Data were collected during the morning and evening peak hours using low-cost sensors, with an average trip distance of 7.50 km. On average, buses exhibited the highest mean PM_2.5 concentration (25.0 $\frac{\mu g}{m^3}$), followed by subways (17.0 $\frac{\mu g}{m^3}$), taxis (14.4 $\frac{\mu g}{m^3}$), cycling (13.5 $\frac{\mu g}{m^3}$), and walking (8.80 $\frac{\mu g}{m^3}$). Pearson correlation analysis showed a strong relationship between traffic volume and PM concentrations in taxi and bus modes (r = 0.78 and 0.56, respectively). Subway commuters experienced the lowest PM_2.5 inhalation dose (2.50 μg), whereas bus commuters experienced the highest (6.20 μg). Pedestrians had the highest average inhalation dose of PM_2.5 with 20.7 μg due to longer trip durations. The daily average PM_2.5 levels in all transportation modes exceeded the WHO thresholds by 1.60 times. These findings offer crucial insights into personal exposure concentrations among commuters and serve as a basis for effective air quality management plans and broader global investigations of air pollution.