Development of aWearable Device for Precise Assessmentof Particle Deposition in the Human Respiratory System

Abstract The adverse respiratory health effects of particulate matter (PM) are well documented, yet real-world exposure and deposition within the human respiratory system remain poorly quantified. Here, we report a wearable device capable of simultaneously collecting PM from inhaled and exhaled breath to directly assess particle deposition under real-world conditions. Designed as a face mask, the device draws ambient air for inhalation while capturing exhaled aerosol, enabling direct comparison between inhaled and exhaled particles. Laboratory validation confirmed efficient collection of exhaled particles with minimal interference from ambient air. We deployed the device in subway environments, where 12 healthy volunteers participated in real-world exposure scenarios. Distinct differences in particle-size distributions between inhaled and exhaled breath were observed, indicating particle deposition and transformation within the respiratory tract. On average, ∼66% of inhaled PM is deposited in the respiratory system, with the highest deposition for particles smaller than 1.0 μm (PM1). Elemental analysis showed that metallic elements, including Fe, Cu, and Pb, dominated subway PM, and their deposition varied with individual characteristics such as lung function and exercise habits. These findings provide real-time evidence of PM deposition in humans and highlight the potential of wearable technologies for real-time assessment of air-pollution exposure and health risks.