Characteristics of PM2.5, CO2 and particle-number concentration in mass transit railway carriages in Hong Kong

Abstract

Fine particulate matter (PM) levels, carbon dioxide (CO) levels and particle-number concentrations (PNC) were monitored in train carriages on seven routes of the mass transit railway in Hong Kong between March and May 2014, using real-time monitoring instruments. The 8-h average PM levels in carriages on the seven routes ranged from 24.1 to 49.8 µg/m, higher than levels in Finland and similar to those in New York, and in most cases exceeding the standard set by the World Health Organisation (25 µg/m). The CO concentration ranged from 714 to 1801 ppm on four of the routes, generally exceeding indoor air quality guidelines (1000 ppm over 8 h) and reaching levels as high as those in Beijing. PNC ranged from 1506 to 11,570 particles/cm, lower than readings in Sydney and higher than readings in Taipei. Correlation analysis indicated that the number of passengers in a given carriage did not affect the PM concentration or PNC in the carriage. However, a significant positive correlation (p < 0.001, R = 0.834) was observed between passenger numbers and CO levels, with each passenger contributing approximately 7.7-9.8 ppm of CO. The real-time measurements of PM and PNC varied considerably, rising when carriage doors opened on arrival at a station and when passengers inside the carriage were more active. This suggests that air pollutants outside the train and passenger movements may contribute to PM levels and PNC. Assessment of the risk associated with PM exposure revealed that children are most severely affected by PM pollution, followed in order by juveniles, adults and the elderly. In addition, females were found to be more vulnerable to PM pollution than males (p < 0.001), and different subway lines were associated with different levels of risk.

Characterization of Urban Subway Microenvironment Exposure—A Case of Nanjing in China

“…Nowadays, field measurement campaigns are commonly deployed for micro-environmental characterization of urban subway systems [16,53,65]. Data obtained in these campaigns could then serve for the evaluation or internal correlations of sub-MEs [42,66]. The findings of this research therefore make them possible to be the foundation of sub-ME-related standards or norms in the future.…”

“…Similarly, Vânia Martins et al demonstrated that ventilation and air conditioning systems could improve subway air quality [11]. Non-ambient sources are main significant contributors to total metro PM exposure [31,42], including emissions from rail mechanical abrasion, and dust particle resuspensions from passenger activities [5,43]. It is therefore recommended to adopt some air protective solutions in station halls or platforms, such as utilizing air sterilization apparatus, strengthening dustproof function through grid design, installing platform screen doors (PSD), and reducing combustion sources as much as possible [35].…”

Exploratory Research of CO2, Noise and Metabolic Energy Expenditure in Lisbon Commuting

“…A study conducted inside Hong Kong buses has shown that high CO 2 averages of 3692 ppm and brief peaks such as 5773 ppm are possible. Other similar studies inside public transportation have reported lower averages with ranges from 714 to 1801 ppm [3]. These values do not present serious health risks, as they do not come close to the short term exposure limit (STEL) of 30,000 ppm established by the U.S. Occupational Safety and Health Administration (OSHA).…”

“…This was expected, as the school period is often associated with busier public and private transportation. CO 2 concentrations inside the metro platform and metro carriage presented lower concentrations than the Shanghai metro system carriages [3]. We averaged the median values for both periods, giving us a concentration of 757.5 ± 135.5 ppm, while the Shanghai metro carriages had mean values of 1253.1 ± 449.1 ppm [35].…”

Ventilation inlets design based on ventilation performance assessment using a dimensionless time scale

“…particles) to minimize exposure risks to occupants. 6–9 Indoor CO 2 can be considered as a good indicator of IAQ, 10–12 especially in the high-density buildings, 13–18 where the CO 2 emitted by occupants can be seen as the main indoor pollutant. For instance, IAQ is considered acceptable by maintaining a steady-state CO 2 concentration no greater than 700 ppm above outdoor air level in a living space, based on the ASHRAE 62–2013 Ventilation Standard.…”