Descriptive statistics of exposure and health data
During the year 2018, the basic information of subjects was shown in Table1. Of the 428 participants, 43% were female. Mean age of total participants was 56.24±16.52. The age ranged from 18 to 86. Mean height and weight were 166.28±8.65 and 60.27±8.82, respectively. Besides, BMI was 24.15±3.12. The PEF in summer and winter were 5.17±3.29 and 4.32±1.88, respectively. And FEV1 were 2.63±0.73 and 2.21±0.75.The detailed characteristics and FVC, FEV1/FVC and FEF25-75 index were also summarized in Table2. The difference of FEV1, FEV1/FVC and FEF25-75 were statistically significant in summer and winter (P<0.01).
The associations between temperature and air pollution
Daily average concentrations of air pollutants during this study period are shown in Fig2.The concentrations of SO2, NO2 , PM2.5 and O3 were highest on 27th, 22th,27th Dec and 8th Aug,respectively. Characteristics of temperature and air pollutants during the two periods are presentd in Table 3 and Table 4. The daily mean temperature was 30.35±2.24℃ in summer and 1.02±3.29℃ in winter. And the daily mean concentrations of PM2.5, SO2 ,NO2 and O3 were 31.13±10.07μg/m3, 7.64±1.39μg/m3 ,142.79±32.98 and 32.78±6.72μg/m3 in summer and 105.56±51.38μg/m3, 23.58±9.66μg/m3, 27.94±10.41 and 69.45±25.45μg/m3 in winter, respectively. The temperature and concentrations of O3 in summer were higher than those in winter. The concentrations of SO2, NO2 and PM2.5 were higher in winter than in summer ( P<0.01). Both PM2.5 concentrations were exceeding WHO guideline for PM2.5 (25μg/m3).
The spearman correlation coefficients for pollutans and temperature are presented in Table 5. In summer, PM2.5 were high positively correlated with NO2(rs=0.286) and negative with O3(rs=-0.244). In winter, PM2.5 were positively correlated with NO2(rs=0.705), SO2 (rs=0.588) and temperature(rs=0.23) and negetive with O3(rs=-0.495) in winter. Temperature were positively correlated with O3 and negative with NO2 both in summer and winter. 4.
Correlation between lung functon and air pollutants in different temperature classes
We divided temperature into three classes. In summer, As shown in Table 6, for every 10μg/m3 increase of O3 concentration, PEF, FEV1 and FVC change are -0.149 L/S (-0.351,-0.052,) -0.021 L/S (-0.034,-0.008), and -0.019L/S (-0.033,-0.006) in normal group. PEF, FEV1 and FVC change amount are -0.011 L/S (-0.005,-0.026), -0.012 L/S (-0.006,-0.017) and 0.01 L/S (0.004,0.016) in higher temperature group. In Winter (Table 7), For every 10μg/m3 increase of PM2.5, PEF, FEV1 and FVC change amount are -0.052 L/S (-0.015,-0.088), -0.008 L/S (-0.014,-0.002) and -0.008 L/S (-0.0001,-0.016) in higher temperature group. FEV1 change is -0.007 L/S (-0.015,-0.001) in normal temperature group.
Analysis of the effects of PM2.5 and Temperature on lung function in different pullutant model
Table 8. shows the relationship between air pollutants (PM2.5, SO2 ,NO2 and O3) and temperature on lung function, In winter, a 10 μg/m3 increase of PM2.5 was associated with a decrease of -0.015 L/S(-0.028,-0.002) and -0.007 L/S (-0.012,-0.001) in PEF and FEV1, respectively. After adjusting for SO2, change of -0.022 L/S (-0.043,-0.001) and -0.010 L/S (-0.011,-0.009) respectivly, in two-pollutant model. In summer, a 10 μg/m3 increase of O3 was associated with a decrease of -0.005 L/S (-0.009,-0.002) and -0.062 L/S (-0.093,-0.031) in PEF and FEV1, respectively. A 1 ℃ increase in temperature and 10 μg/m3 increase of O3 were accosiated with a -0.122 L/S (-0.160,-0.084) decreas in FEV1.Moreover, the interactive effects between temperature and PM2.5 in winter PEF and FEV1 were found to be significantly positive, an increae in temperature reduced the adverse effect of PM2.5 on lung function. A 1 ℃ increase in temperature and 10 μg/m3 increase of PM2.5 were accosiated with a 0.007 L/S (0.001,0.012) increase in PEF.
Lagged effects of PM2.5 and Temperature on Lung function
Fig. 3 shows the lag effect of PM2.5 and temperature on PEF, FEV1and FEV1/FVC. The change in PEF was significantly negatively associated with the concentrations of PM2.5. The change was greatest on lag1(-0.006[95% CI:-0.012,-0.001]).For FEV1,FEV1/FEVC and FEF25-75,the effect of PM2.5 was greatest on Lag 0(-0.003[95% CI:-0.005,0.000],-0.058[95%CI:-0.095,-0.022 and-0.002[95% CI:-0.003,0.000]), and the different were significantly.
In addition, the cumulative lags of temperature (Lag0) were more corelated with both PFE and FEV1/FVC. The temperature of Lag 1 was related to FEV1 and FEF25-75.