An accurate estimation of human exposure to ambient air pollution is crucial for air pollution health studies. Time-activity patterns may introduce substantial uncertainties in exposure estimation. As smartphones are becoming increasingly popular and their ownership is becoming ubiquitous in the US. Virtually all smartphones can collect location data, and such data is continuously somewhere. Therefore, it is clear that such stored location data has the potential to be used for characterizing an individual's time-activity patterns for air pollution health studies. However, studies on the accuracy and feasibility of using a smartphone's location data in air pollution exposure estimation are still limited. Here, a pilot study was conducted to evaluate the accuracy of the iPhone's Significant Location (iSL) data, in capturing an individual's time-activity patterns. Specifically, iSL data collected from a single individual were compared with reference GPS data to evaluate the ability of iSL in capturing: 1) all microenvironments the subject visited during the study period; 2) the duration and frequency the subject spent in each microenvironment, if the location is labelled as significant and captured by iSL; and 3) the impact of neglecting time-activity pattern on the subject's air pollution exposure estimates. The results showed a favorable performance of the iSL data, which accurately captured the time the subject spent in 16 microenvironments encompassing 93% of all time during the study period. To further understand the availability of iSL data, an online survey was conducted among 349 participants. Among the surveyed users, 72% have iSL data available which highlighted the potential substantial coverage of iSL data. With the popularity of iPhone, detailed significant location data could be available for a considerable portion of the population, and such iSL data may have great potentials for improving retrospective air pollution exposure estimation.


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Graduation Date





Yu, Haofei


Master of Science (M.S.)


College of Engineering and Computer Science


Civil, Environmental and Construction Engineering

Degree Program

Environmental Engineering; Environmental Engineering Sciences




CFE0008828; DP0026107



Release Date

December 2021

Length of Campus-only Access


Access Status

Masters Thesis (Open Access)