Micro-mobility users’ exposure to PM2.5 pollution: A scoping review

Abstract

Micro-mobility (MM) modes, such as bicycles, e-scooters, and motor-scooters, offer sustainable transportation alternatives but may expose users to elevated levels of traffic-related air pollution, particularly fine particulate matter (PM2.5). Existing reviews have predominantly focused on bicyclists or comparisons between active and non-active transportation modes, with limited attention to the MM modes. This scoping review addresses this gap by synthesizing the literature on PM2.5 exposure among MM users. Peer-reviewed articles published in English between 2000 and 2021 were systematically identified through Web of Science, with inclusion criteria targeting studies that reported PM2.5 exposure in MM users. Data extraction emphasized geographic location, PM2.5 exposure metrics, and study design. Analysis of 52 eligible studies revealed a strong geographic bias toward the Global North, with minimal representation from the Global South. The findings also uncovered disparities in PM2.5 exposure levels across MM modes and regions, indicating that the assumed universal health benefits associated with MM might not be equally experienced. Most studies relied on pre-determined measurement routes under controlled conditions to ensure consistency in exposure assessments; however, a smaller subset used free-living settings, likely offering more realistic insights into user behavior and exposure profiles. While PM2.5 concentration was the primary focus, an increasing number of studies incorporated inhalation exposure metrics by estimating or measuring ventilation rates. Future research should prioritize underrepresented MM modes and regions, employing inclusive methodologies that account for behavioral and environmental contexts. This approach is essential for understanding diverse usage patterns and exposure risks, ultimately informing strategies to mitigate the health impacts of PM2.5 on MM users.