Abstract
City dwellers’ personal exposure to PM is influenced by numerous daily activities in multiple indoor and outdoor micro-environments (MEs). This study assessed the integrated personal exposure to PM across urban MEs together with the recording individual time-activity patterns. We evaluated simultaneously the exposure to PM2.5, black carbon (BC), and ultrafine particles (UFPs) in the Central Business District (CBD) area of Singapore. In addition, we quantified the lung-deposited surface area (LDSA) concentration, which is an indicator of the potential health impacts of UFPs. The field study was conducted over a 7-km walking route to identify air pollution hotspots. Subsequently, the personal exposure to PM2.5, BC, and UFPs was measured at five selected hotspots for 1 hour each and across indoor and outdoor MEs during diverse daily human activities for 24 hours. The PM concentrations were found to vary considerably in both space and time in the CBD area. During the 1-hour personal exposure measurement, extremely high concentrations of PM2.5 (215 ± 129.5 µg m–3 and 36.4 ± 12.5 µg m–3) and BC (20.9 ± 10.4 µg m–3 and 18.1 ± 12.0 µg m–3) were observed at a temple and a bus stop, and elevated UFP number concentrations (320.8 ± 131.1 × 103 # cm–3) and high LDSA concentrations (564.6 ± 276.5 µg2 cm–3) were measured at a food court. The estimated potential health risk suggests that the continued inhalation of large amounts of PM2.5 emitted from combustion sources is likely to lead to adverse long-term health effects among the exposed individuals. Overall, we provide insight into an individual’s total exposure to PM based on time-activity patterns. The results of this work form a scientific basis for developing air pollution control measures to mitigate personal exposure to PM on a city scale.
Highlights
Many epidemiological and toxicological studies conducted worldwide indicated that human exposure to high levels of airborne particulate matter (PM), those particles with aerodynamic diameters less than 2.5 μm (PM2.5), can have adverse human health effects (Pope et al, 1995; World Health Organization (WHO), 2013; Kim et al, 2015)
Our study reveals that the PM2.5 concentrations were the lowest in the study area during the evening hours, which is attributed to changes in the traffic composition and in PM sources during the day
There was a large volume of buses, taxis, and cars during morning and afternoon hours while a relatively high number of trucks and utility vehicles were during the afternoon hours
Summary
Many epidemiological and toxicological studies conducted worldwide indicated that human exposure to high levels of airborne particulate matter (PM), those particles with aerodynamic diameters less than 2.5 μm (PM2.5), can have adverse human health effects (Pope et al, 1995; WHO, 2013; Kim et al, 2015). The focus of several air pollution studies has shifted from PM2.5 mass concentration to more specific metrics such as the mass concentration of black carbon (BC) and ultrafine particles (UFPs) due to their strong association with negative health effects (e.g., Heal et al, 2012; Wu et al, 2015). Recent studies have indicated that even at a concentration below current air quality regulations (e.g., Environmental Protection Agency (EPA) regulations), health effects persist (Wellenius et al, 2012; Rice et al, 2013).
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