Effects of PM2.5 components on peak expiratory flow among COPD patients: A panel study

<bold>Background:</bold> Fine particulate matter (PM_2.5) exposure has been associated with lung function decline, and patients with chronic obstructive pulmonary disease (COPD) are susceptible groups. However, the differential effects of PM_2.5 components on lung function in COPD are not clear. We aimed to examine the associations between PM_2.5 components and peak expiratory flow (PEF) among clinically-stable COPD patients. <bold>Methods:</bold> In this panel study, we recruited 32 COPD patients in Beijing between March and July 2018. Participants were followed up for four one-month periods across different seasons. Daily PEF was measured using a peak flow meter in the morning. Daily mean concentrations of PM_2.5 components, including SO4^2-, NO^3-, NH⁴⁺, organic matter (OM), and black carbon (BC), were obtained from the Tracking Air Pollution in China (TAP) database and assigned to residential address at a 10-km resolution. Linear mixed model with a subject-specific random intercept was used to investigate the association between PM_2.5 components and PEF. <bold>Results:</bold> The mean age of participants was 64.8±5.7 years, and most of them were men(90.6%) and smokers(87.5%). We found negative associations between 5-day moving-average concentrations (lag1-5) of PM_2.5 components and daily PEF. PEF changes associated with each interquartile range(IQR) increase in PM_2.5 components were -10.83(95%CI:-14.58, -7.08) L/min for SO4^2-, -6.70(95%CI: -10.66, -2.73) L/min for NO^3-, -6.50(95%CI:-10.24, -2.77) L/min for NH⁴⁺, -8.23(95%CI:-12.48, -3.97) L/min for OM, and -9.36(95%CI:-13.39, -5.34) L/min for BC. <bold>Conclusion:</bold> Short-term exposure to PM_2.5 and its components, particularly SO4^2- and BC, were associated with decreased PEF in COPD patients.