Abstract Rationale Fine particulate matter (PM2.5) is a well-established contributor to adverse lung health outcomes. Individual exposure varies among children living in the same urban communities due to differences in location, daily travel, and activity patterns. During activity, increased ventilation can elevate the inhaled dose of air pollutants. While physical activity benefits health, its risks during high pollutant exposure in children remain unclear. Our objectives were to 1) compare PM2.5 concentrations across locations and modes of transit and 2) assess how activity level (metabolic equivalents of task METs) varies by location and transit mode among students who live in the same urban environment. Methods We recruited 56 high school students from June 2023 to June 2025. Each student underwent a 72-hour sampling period with an ultrasonic personal air sampler (UPASv2+, Access Sensor Technologies), GPS tracker, and Polar M430 accelerometer that measured METs per second, yielding 4,032 hours of monitoring data. Daily questionnaires documented transportation modes, duration, and locations. Six location categories were created: home, school, morning commute, other transit, outdoors, and other indoors (i.e. indoor locations besides home and school). Statistical analyses were conducted in R. Results Fifty-six students ages 14-21 participated. Most were female (66.1%) and Hispanic (94.6%). As shown in Table 1, PM2.5-location analysis indicated that median PM2.5 was highest during other transit (9.9μg/m3, interquartile range IQR 12.9) and at home (9.6μg/m3, 13.2), and lowest at school (5.9μg/m3, 6.2) and other indoors (5.7μg/m3, 9.8). Analysis by transit mode revealed that median PM2.5 was highest on the subway (15.6μg/m3, 16.8), followed by biking (9.4μg/m3, 4.4), and lowest while walking (5.6μg/m3, 7.2) and by car (4.4μg/m3, 4.1). Physical activity analysis showed that median METs were highest outdoors (2.9, 1.87) and during other transit (2.7, 1.13), and lowest at school (2.0, 0.71) and home (1.3, 0.27). Median METs were highest while biking (3.1, 1.41), followed by subway (2.7, 0.90), and lowest while traveling by car (2.3, 0.46) and bus (2.2, 0.82). Conclusion Students experienced significant variability in PM2.5 by location and transit mode, with highest concentrations observed during commuting, particularly while on the subway and when biking. Moreover, periods of increased activity frequently coincided with greater PM2.5 exposure, most noticeably while commuting. These findings highlight the importance of understanding transit behaviors, activity patterns, and pollutant levels at different locations to accurately assess urban youth exposure. Future directions include calculating personal inhaled pollutant dose and evaluating associations with lung function and airway inflammation. This abstract is funded by: Columbia University Irving Institute for Clinical and Translational Research, NHLBI
Giri et al. (2026) studied this question.