Indoor PM2.5 levels and self-reported health symptoms in office workers during the haze seasons in Chiang Mai Thailand

Abstract This study investigated the impact of fluctuating indoor air-conditioned environments and seasonal air pollution on physical symptoms among office workers in Chiang Mai, Thailand. Using a longitudinal repeated measures design, the same cohort of 27 office workers was monitored over an 8-week period to capture variations between seasons. Indoor air quality parameters, including indoor PM2.5, CO 2 , temperature, and humidity, were monitored continuously during office hours. The multivariable binary logistic regression analysis, adjusted for age, gender, and office location, demonstrated that indoor PM2.5 concentrations were significantly associated with an increased likelihood of nasal symptoms (adjusted OR = 3.99, 95% CI: 1.48–10.76, p = 0.01). Furthermore, significant associations were observed with relative humidity and temperature, while no other statistically significant associations were found for ocular, respiratory, or skin symptoms in the balanced 25-participant cohort. These findings highlight that indoor fine particulate matter is a primary environmental factor related to health complaints in air-conditioned office settings, underscoring the need for targeted workplace policies during seasonal pollution episodes.