Abstract
The spatiotemporal locations of large populations are difficult to clearly characterize using traditional exposure assessment, mainly due to their complicated daily intraurban activities. This study aimed to extract hourly locations for the total population of Beijing based on cell phone data and assess their dynamic exposure to ambient PM2.5. The locations of residents were located by the cellular base stations that were keeping in contact with their cell phones. The diurnal activity pattern of the total population was investigated through the dynamic spatial distribution of all of the cell phones. The outdoor PM2.5 concentration was predicted in detail using a land use regression (LUR) model. The hourly PM2.5 map was overlapped with the hourly distribution of people for dynamic PM2.5 exposure estimation. For the mobile-derived total population, the mean level of PM2.5 exposure was 89.5 μg/m3 during the period from 2013 to 2015, which was higher than that reported for the census population (87.9 μg/m3). The hourly activity pattern showed that more than 10% of the total population commuted into the center of Beijing (e.g., the 5th ring road) during the daytime. On average, the PM2.5 concentration at workplaces was generally higher than in residential areas. The dynamic PM2.5 exposure pattern also varied with seasons. This study exhibited the strengths of mobile location in deriving the daily spatiotemporal activity patterns of the population in a megacity. This technology would refine future exposure assessment, including either small group cohort studies or city-level large population assessments.
Highlights
Introduction iationsDetailed exposure assessment is the basis of air pollution-related epidemiological studies [1]
PM2.5 based on hourly cell phone locations
Compared to previous studies in China or other countries, the seasonal and yearly land use regression (LUR) models established in this study were all excellent [27,34,35,36,37,38]
Summary
Detailed exposure assessment is the basis of air pollution-related epidemiological studies [1]. Accurately characterizing the spatiotemporal location of people and the corresponding pollution concentration are two fundamental procedures in exposure assessment. The location of people and the concentration of pollution are always varying with time and are difficult to describe in detail. The geographic locations of people are changing due to human activities, mostly in a home-office, home-schooling, or in other daily patterns [3]. The outdoor air pollution concentration changes spatially along the travel route, with higher concentrations near traffic roads or industry settings and lower concentrations farther away from emission sources [4]. The air pollution concentration at a Licensee MDPI, Basel, Switzerland
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