Ambient PM2.5 and respiratory tract disorder–related outpatient visits among healthcare workers: an ecological time-series study

INTRODUCTION: Ambient fine particulate matter (PM2.5) is associated with adverse respiratory outcomes, yet evidence among healthcare workers remains limited. This study examined temporal associations between weekly ambient PM2.5 concentrations and respiratory tract disorder (RTD)-related outpatient visits among healthcare workers, an occupationally active urban population potentially affected by ambient air pollution. METHODS: An ecological time-series study was conducted among healthcare workers at a 1,000-bed tertiary-care hospital in Bangkok, Thailand, from November 2018 to April 2019. RTD- and respiratory tract symptom (RTS)-related outpatient visits were identified using ICD-10 codes (J00-J99) from electronic medical records. Weekly average ambient PM2.5 concentrations were obtained from the nearest national monitoring station. Weekly outpatient visit counts were analysed using Poisson or negative binomial regression models and expressed as incidence rate ratios (IRRs) per 10 µg/m³ increase in PM2.5 concentration, adjusted for temporal trends. RESULTS: Among 12,458 healthcare workers, short-term increases in weekly ambient PM2.5 concentrations were associated with higher outpatient visit counts for overall RTDs (IRR 1.139, 95% CI 1.059-1.225), common cold (1.164, 1.082-1.252), allergic rhinitis (1.240, 1.126-1.365), sinusitis (1.168, 1.017-1.342), and asthma (1.429, 1.003-2.037). Significant associations were also observed for upper respiratory symptoms including sneezing, sore throat, cough, and shortness of breath. CONCLUSIONS: Short-term increases in ambient PM2.5 concentrations were temporally associated with higher respiratory outpatient visits among healthcare workers. These findings extend evidence regarding air pollution and respiratory health to an understudied occupational population and reinforce the public health importance of continued air quality management in urban environments.