Short-term and long-term effects of PM_2.5 on acute nasopharyngitis in 10 communities of Guangdong, China

Objectives: We aimed to assess the effects of short-term and long-term exposure to ambient fine particle matter (PM_2.5) on acute nasopharyngitis. Methods: A total of 9468 participants aged 18 years and above were recruited from 10 communities in four cities of Guangdong, China during the baseline survey in 2014, and they were followed-up from January 2015 to December 2016. Air pollution exposure was assessed based on the daily concentrations (short-term) and annual concentrations (long-term) of the nearby air monitoring station and the survey date. A mixed-effect logistic model and Cox proportional hazards model were used to quantify the short-term and long-term associations after adjustment for potential confounding factors. Results: Significantly positive associations were found between both short-term and long-term exposures of PM_2.5 and acute nasopharyngitis. The adjusted odds ratio was 1.15 (95% CI: 1.07, 1.23) for each 10 μg/m³ increase in daily PM_2.5 at lag2 day (short-term effects), and the hazard risk was 1.18 (95% CI: 1.10, 1.25) for each 10 μg/m³ increase in annual PM_2.5 (long-term effects). Stronger associations between short-term PM_2.5 exposure and acute nasopharyngitis were observed among men (OR = 1.10; 95% CI: 1.04, 1.17) and participants aged above 65 years (OR = 1.13; 95% CI: 1.04, 1.23) in the stratified analyses. No significant association was found in women (OR = 1.00; 95% CI: 0.92, 1.10) or young participants ≤65 years (OR = 0.96; 95% CI: 0.88, 1.04). However, for the long-term exposure, the hazard risk was higher for participants younger than 65 years (OR = 1.22; 95% CI: 1.12, 1.32) than the older group (OR = 1.11; 95% CI: 1.00, 1.24). Conclusion: This study indicates that both short-term and long-term exposures to higher concentrations of PM_2.5 could increase the risk of acute nasopharyngitis.