Unacknowledged health costs of subway transportation: Commuting time dominant environmental inequality in PM2.5 exposure

Introduction

The subway network offers economical and swift transportation for long-distance commuters, simultaneously mitigating urban congestion and environmental challenges in sprawling metropolises. Nonetheless, studies have revealed that subway represent a microenvironment with heightened exposure to fine particulate matter (PM_2.5), a facet of air pollution overlooked by the majority of commuters. Focusing on the case of Beijing's subway commuters, we assess the health and economic impact of personal exposure to PM_2.5 during their commuting, as well as the distributional effects of these impacts across subgroups of populations with different daily commuting durations.

Method

This study adopts an integrated process to estimate the health outcomes and associated economic loss caused by subway commutes under different exposure scenarios. The overall daily exposure was estimated by aggregating exposure in different microenvironments using the microenvironmental exposure model. The health impact was then evaluated using the integrated exposure-response (IER) model. The economic value of the health impact was assessed based on the value of statistical life (VSL) of the affected population.

Result

Our findings indicate that subway commutes lead to an increase of 11.6% and 26.3% in health damage and corresponding economic loss attributable to PM_2.5 exposure through “crowding out” of exposure duration in relatively “cleaner” microenvironments in 2017 and 2020, respectively. Long-distance commuters who travel over 100 min per day, make up 25% of subway commuters and are disproportionately responsible for 40% of the total health damages and economic losses caused by subway PM_2.5 exposure. Reducing PM_2.5 concentration in subway cabins can more effectively offset the additional impacts brought about by the extended and rather inelastic subway commuting.

Conclusion

The result unearthed by our study advocates for urgent measures to ameliorate the air quality within subway systems, a move that promises to mitigate the unequal burdens and rectify the inequities borne by at-risk demographics.