Assessment of personal and residential outdoor fine particulate matter exposure using low-cost sensors in a long-Covid patient population

Abstract

Understanding the relationship between residential outdoor and personal PM2.5 exposure is essential for accurately characterizing individual exposure, identifying key pollution sources, and developing targeted mitigation strategies. This study examines residential and personal PM2.5 exposure levels and their interrelation in a long COVID population in the Netherlands. Residential outdoor PM2.5 exposure was monitored using 73 low-cost continuous sensors deployed over an average of 131 days per participant. In parallel, 264 24-hour personal PM2.5 measurements were collected using an Ultrasonic Personal Air Sampler (UPAS), with multiple measurements per participant spanning different seasons. Participants completed a detailed exposure questionnaires to document potential sources and behavioral patterns. Overall, personal PM2.5 exposure levels (mean: 25.4 µg/m3) were higher than residential outdoor levels, with a mean difference of 18.4 µg/m³. When twelve influential personal measurements >50 µg/m3 were excluded, the mean difference decreased to 10.1 µg/m3. The 172 paired 24-hour measurements of personal and residential PM2.5, revealed a moderate overall correlation (r = 0.27), with a stronger longitudinal within-person correlation (r = 0.39). Key contributors to the observed difference between personal and residential outdoor exposure included tobacco smoke exposure, the presence of a fireplace in the home, and increased ambient temperature. These findings suggest that patients in our study are exposed to PM2.5 concentrations higher than the WHO air quality guidelines (5 ug/m3) potentially exacerbating already existing health problems. Furthermore, we identified environmental and behavioral factors affecting their exposure patterns providing opportunities to mitigate PM2.5 exposures by long COVID patients.