What is it about?

Public transport is vital for reducing emissions and building sustainable cities, but the air we breathe inside buses and trains often goes unnoticed. In San José, Costa Rica, we measured air quality in air-conditioned public transport and found carbon dioxide levels up to ten times higher than recommended limits. In the tropical climate, windows remain closed and air is mostly recirculated to save energy, resulting in poor ventilation. This can cause discomfort, fatigue, and potential health risks for passengers. Our findings highlight the need to improve air circulation in public transport to safeguard health while maintaining energy efficiency. Smarter ventilation strategies can make daily travel safer, more comfortable, and more sustainable for everyone.

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Why is it important?

Air quality in enclosed public transport vehicles directly affects passenger health, yet it is often overlooked in sustainability efforts. In tropical cities, sealed and air-conditioned buses and trains can trap exhaled air, leading to poor ventilation and high carbon dioxide levels. This study draws attention to the health risks of breathing stale air in daily commutes and underscores the urgent need for ventilation standards tailored to hot, humid climates. By addressing this gap, our work supports healthier, safer, and more sustainable indoor environments for urban mobility.

Perspectives

I use buses and MRTs every day to get to work in a large tropical city. I enjoy the cool comfort inside, but I often wonder about the air we’re actually breathing, especially during the monsoon, when flu and other viruses spread easily. COVID-19 was a clear reminder of how important clean indoor air and good ventilation are. When I see more people wearing masks, I can’t help feeling uneasy. We need efficient, low-carbon public transport, but also systems that keep the air fresh and passengers healthy. Sustainable mobility shouldn’t come at the cost of our well-being.

Dr. Jan-Frederik Flor
Taylor's University

Read the Original

This page is a summary of: Ventilation Challenges in Costa Rican Urban Public Transport: Implications for Health and Sustainable Mobility, Atmosphere, August 2025, MDPI AG,
DOI: 10.3390/atmos16091013.
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