Mobility-driven estimate reveals elevated air pollution exposure and socioeconomic disparities beyond residence-based approaches in Boston

Abstract

Background: Residence-based air pollution exposure assessments ignore daily human mobility and may misrepresent exposure levels and disparities across population groups. Objective: We hypothesize that incorporating high-resolution mobility trajectories into exposure modeling will reveal higher average PM2.5 exposures and uncover sociodemographic disparities that traditional residence-based methods underestimate or conceal. Methods: We analyzed 155,000 trip records from 990 Boston-area participants (June–December 2023) collected via smartphone GPS, linked to PM2.5 measurements from 294 calibrated PurpleAir air quality sensors collected at 2-min intervals. For each stay location, we computed a daily adjusted exposure as the average PM2.5 within a 4 km buffer minus the region’s daily average. We compared these mobility-informed exposures to home-based estimates, assessed temporal (weekday vs. weekend, peak vs. off-peak) and spatial variability (Moran’s I), and used weighted least squares regressions and t-tests to evaluate differences across race, income, education, age, and occupation. Results: Mobility-informed exposures averaged 0.10 µg/m3 higher than residence-based estimates on weekdays (up to 0.45 µg/m3 on high-pollution days). Employed and higher-income individuals, as well as White participants, experienced significantly elevated exposures during peak travel hours (up to +0.30 µg/m3; p < 0.01). Spatial clustering of mobility exposures was stronger on weekdays (Moran’s I = 0.4) than weekends (I = 0.2), and regression coefficients confirmed systematic underestimation by traditional methods. Significance: These findings demonstrate that neglecting mobility systematically underestimates exposure levels and obscures environmental injustices. Impact statement: Integrating dynamic mobility data with hyperlocal air quality monitoring provides a refined framework for accurate exposure assessment, informing equitable public health policies and targeted interventions.