In this research, MIT scholars acquired geographically and time-referenced 3G mobile traffic data from several operators. This included data from all types of mobile devices such as phones and tablets, corresponding to several million people in NYC. The dataset enabled the collective tracking of the spatial and temporal locations of NYC's population. This enabled researchers to assign corresponding time and geographically variable air pollution exposure values to residents, in order to map New York City's population with their air pollution exposure levels.
Since mobile phone operators provided normalized data aggregated at the cell tower level to the researchers, the users were anonymized. However, the study does not detail how these datasets were procured, and what data-sharing agreement was forged between the mobile phone operators and the researchers.
This research attempts to use digital datasets to "predict the impacts of the urban environment on human health." In this study, where researchers use mobile phone data to map the movements of several million people, important insights into the risks of air pollution can be gleaned, which can then inform environmental and public health policy.