Assessing Inhaled Dose of Pollutants Across Activities and Environments Using a Wearable Environmental Monitor: A Pilot Study

Background: Air pollution is a global health threat, with nearly the entire world's population breathing air that exceeds the World Health Organization guidelines. Traditional stationary monitoring systems are inadequate for evaluating exposure at an individual level. In addition, the actual inhaled dose also depends on the ventilation of an individual. Aim: In this study, a newly designed wearable environmental monitor, paired with a commercial heart rate monitor, was used to assess individual exposure during various activities, both indoor and outdoor, and compute the inhaled dose of pollutants. Methods: The protocol consists of 5 different activities including light computer work, rest, indoor treadmill walking, stairs climbing, and outdoor walking. Data on air pollution and heart rate were collected, and the inhaled dose of CO2 and PM2.5 was calculated using an existing model of minute ventilation, and tabulated data. Results: Variations in heart rate and in pollutants concentration across different participants and activities were found. Ambient PM2.5 levels (median 9.5-13.2 μg/m3) were below the WHO 24-hour guideline (15 μg/m3) but above the annual threshold (5 μg/m3), while CO2 concentrations (563-1075 ppm, IQR up to 1270 ppm) indicated occasional insufficient indoor ventilation. Activity type had a significant impact on inhaled doses of CO2 (p < 0.001) and PM2.5 (p = 0.0011). Higher doses of CO2 were found during indoor treadmill walking at 4 km/h and 5 km/h with respect to outdoor walking (p = 0.0225 and p = 0.0119, respectively), while resting led to a significantly lower inhaled dose only when compared to indoor treadmill walking at 5 km/h (p = 0.0146). PM2.5 inhalation was significantly higher during outdoor walking with respect to the seated condition of rest and light activity (p = 0.0177 and p = 0.0065, respectively), while stair climbing induced a significantly higher inhaled dose only with respect to rest. Conclusion: The wearable environmental device measures real-time pollution, and when integrated with physiological sensors, it enables personalized inhaled dose estimation. This approach offers a valuable tool for managing individual exposure, especially during physical activity.