Objective: To evaluate the effects of indoor and outdoor PM2.5 (fine particulate matter, particulate matter with an aerodynamic diameter ≤ 2.5 µm) on lung function of college students in autumn and winter in Wuhan.
Methods: In this panel study, 37 college students (excluded subject of respiratory disease and smoking history) aged 19 - 21 were investigated by cluster sampling in a university in Wuhan. The follow-up study lasted for 28 days in total, including two study periods, Oct. 29 to Nov. 11, 2009 (autumn) and Dec. 23, 2009 to Jan.5, 2010 (winter), the peak expiratory flow (PEF) of the college students were measured daily in the morning and evening in the university. PM10 and PM2.5 were monitored indoors and outdoors. The effects of PM on lung function of college students were analyzed by using generalized estimating equation (GEE).
Results: Average daily concentrations of indoor, outdoor PM2.5 in autumn were (91.3 ± 43.7) and (104.2 ± 49.4) µg/m(3) respectively, while in winter the concentrations of indoor and outdoor PM2.5 were (110.6 ± 42.3) and (143.5 ± 51.2) µg/m(3). The single pollutant model showed that in winter, the evening PEF decrement was significantly associated with increasing outdoor PM2.5. With an increase of 10 µg/m(3) outdoor PM2.5, the PEF measured in the evening decreased 1.27 L/min (95%CI: 0.02 - 2.52 L/min, respectively). Meanwhile, the results showed that 2-days lagged outdoor PM2.5 was also significantly associated with morning PEF. An increase of 10 µg/m(3) 2-days lagged outdoor PM2.5 caused the decrease of 1.82 L/min (95%CI: -3.53 - -0.11 L/min) of PEF measured in the morning. Controlling the influence of gaseous pollutants and building the two pollutants models, the results indicated that no significant changes of PEF of students being exposed to PM2.5 on same day (lag 0) were observed. However, under consideration of SO2 effect, significant association between an increase of 10 µg/m(3) 2-days lagged outdoor PM2.5 and changes of morning PEF (-1.81 L/min, 95%CI: -3.51 - -0.11 L/min, P = 0.037) was found. The relationship between changes of concentrations and PEF was not observed in autumn in this study.
Conclusion: In our panel study, exposure to outdoor PM2.5 is significantly associated with PEF among college students in winter, but not in autumn.