Hazardous VOCs pollution and health effects in metro carriages in different building climate zones: A comparative study in China

The presence of hazardous volatile organic compounds (VOCs) in metro carriages presents a significant concern for indoor air quality and passenger health, particularly within confined transportation environments. This study conducted a comparative analysis of nine hazardous VOCs pollution in metro carriages across two building climate zones in China: Chengdu (hot summer and cold winter region) and Changchun (severe cold region). VOC samples were collected across four seasons, covering both peak and off-peak commuting periods. The results indicated that Σ9VOCs concentrations were significantly higher in Changchun compared to Chengdu, particularly during winter, likely due to the influence of heating-related emissions and reduced ventilation. Diagnostic ratio analysis revealed that VOC sources varied between the two cities, with traffic emissions being the dominant contributor in Chengdu, whereas industrial and combustion-related sources played a more prominent role in Changchun. Principal Component Analysis (PCA) further identified key pollutant contributors, with toluene, benzene, and xylene derivatives being predominant in both locations. Health risk assessments demonstrated that while non-cancer risks remained within acceptable limits, benzene exposure contributed to a marginally elevated cancer risk, particularly for children. These findings highlight the necessity of tailored mitigation strategies to combat metro air pollution across different climate zones, promoting safer commuting environments.