Particle exposure and inhaled dose during commuting in Singapore

Publication date: December 2017
Source:Atmospheric Environment, Volume 170
Author(s): Sok Huang Tan, Matthias Roth, Erik Velasco
Exposure concentration and inhaled dose of particles during door-to-door trips walking and using motorized transport modes (subway, bus, taxi) are evaluated along a selected route in a commercial district of Singapore. Concentrations of particles smaller than 2.5 μm in size (PM2.5), black carbon, particle-bound polycyclic aromatic hydrocarbons, number of particles, active surface area and carbon monoxide have been measured in-situ using portable instruments. Simultaneous measurements were conducted at a nearby park to capture the background concentrations. The heart rate of the participants was monitored during the measurements as a proxy of the inhalation rate used to calculate the inhaled dose of particles. All measured metrics were highest and well above background levels during walking. No significant difference was observed in the exposure concentration of PM2.5 for the three motorized transport modes, unlike for the metrics associated with ultrafine particles (UFP). The concentration of these freshly emitted particles was significantly lower on subway trips. The absence of combustion sources, use of air conditioning and screen doors at station platforms are effective measures to protect passengers' health. For other transport modes, sections of trips close to accelerating and idling vehicles, such as bus stops, traffic junctions and taxi stands, represent hotspots of particles. Reducing the waiting time at such locations will lower pollutants exposure and inhaled dose during a commute. After taking into account the effect of inhalation and travel duration when calculating dose, the health benefit of commuting by subway for this particular district of Singapore became even more evident. For example, pedestrians breathe in 2.6 and 3.2 times more PM2.5 and UFP, respectively than subway commuters. Public buses were the second best alternative. Walking emerged as the worst commuting mode in terms of particle exposure and inhaled dose.

Graphical abstract

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