Table 1 summarizes the daily COPD mortality, PM pollution, and weather conditions from 2014–2016 in Zhejiang Province. In the present study, the daily average death count due to COPD was 3, varying from 1 to 7among six cities. The daily 24-hour mean concentrations of PM2.5, PM2.5−10, and PM10 were 41.9, 22.3, and 64.1 µg/m3, respectively. The daily 24-hour mean concentrations among six cities were 29.7 to 56.8 µg/m3 for PM2.5, 16.7 to 30.3 µg/m3 for PM2.5−10, and 50.3 to 87.1 µg/m3 for PM10, respectively. The daily mean temperature, pressure, relative humidity, wind speed and precipitation were 18.3℃, 1011 hpa, 77.3%, 1.88 m/s, and 5.08 mm, respectively. There were significant differences in COPD mortality, PM pollution, and weather conditions (p < 0.01) among six cities except precipitation (p > 0.05).
Table 1
Summary statistics of daily COPD mortality, PM pollutants, and weather conditions in Zhejiang Province, 2014–2016
City | Days | Year | COPD (death/day) | PM2.5 (µg/m3) | PM2.5-10 (µg/m3) | PM10 (µg/m3) | Temperature (℃) | Pressure (hpa) | Relative humidity (%) | Wind speed (m/s) | Precipitation (mm) |
All | 4385 | 2014–2016 | 3 ± 3 | 41.9 ± 27.1 | 22.3 ± 15.8 | 64.1 ± 38.0 | 18.3 ± 8.2 | 1011 ± 9 | 77.3 ± 13.0 | 1.88 ± 0.89 | 5.08 ± 12.2 |
HZ | 1096 | 2014–2016 | 7 ± 3 | 56.8 ± 31.5 | 30.3 ± 19.0 | 87.1 ± 44.7 | 17.8 ± 8.4 | 1011 ± 9 | 74.4 ± 13.9 | 2.15 ± 0.81 | 5.68 ± 11.8 |
JH | 731 | 2015–2016 | 1 ± 1 | 48.9 ± 26.8 | 16.7 ± 13.2 | 65.4 ± 34.8 | 18.8 ± 8.4 | 1009 ± 9 | 75.4 ± 14.0 | 1.70 ± 0.56 | 5.08 ± 11.6 |
LS | 731 | 2015–2016 | 1 ± 1 | 35.5 ± 21.4 | 16.8 ± 9.2 | 52.2 ± 26.9 | 19.4 ± 8.1 | 1009 ± 9 | 75.5 ± 11.3 | 1.05 ± 0.44 | 4.65 ± 10.9 |
NB | 366 | 2016 | 3 ± 2 | 38.5 ± 22.9 | 23.4 ± 12.5 | 61.9 ± 33.1 | 18.3 ± 8.5 | 1015 ± 9 | 77.6 ± 11.2 | 2.55 ± 1.25 | 5.00 ± 14.1 |
TZ | 366 | 2016 | 3 ± 2 | 35.7 ± 19.4 | 24.6 ± 13.0 | 60.3 ± 29.6 | 19.1 ± 8.2 | 1015 ± 9 | 81.9 ± 12.9 | 1.97 ± 0.75 | 4.99 ± 10.8 |
ZS | 1095 | 2014–2016 | 2 ± 1 | 29.7 ± 20.5 | 20.7 ± 15.8 | 50.3 ± 31.7 | 17.4 ± 7.7 | 1012 ± 9 | 81.1 ± 11.6 | 2.01 ± 0.85 | 4.84 ± 13.6 |
F | | | 1272.24 | 157.83 | 108.65 | 145.47 | 7.87 | 60.86 | 47.33 | 261.56 | 0.80 |
P | | | 0.000 | 0.000 | 0.000 | 0.000 | 0.000 | 0.000 | 0.000 | 0.000 | 0.551 |
Table 2 shows the Spearman’s correlation. COPD mortality was significantly correlated with the concentrations of PM2.5 (r = 0.302, p < 0.01), PM2.5−10 (r = 0.282, p < 0.01), PM10 (r = 0.323, p < 0.01), wind speed (r = 0.308, p < 0.01), temperature (r = -0.163, p < 0.01), pressure(r = 0.161, p < 0.01),and relative humidity (r = -0.0683, p < 0.01), but not correlated with precipitation(p > 0.05). In addition, PM2.5 and PM2.5−10, PM2.5 and PM10, and PM10 and PM2.5−10 were highly correlated (r = 0.524, p < 0.01, r = 0.933, p < 0.01, and r = 0.772, p < 0.01). Given that results obtained by combined effects of PM10 with PM2.5 and PM2.5−10 may bring the multicollinearity, we did not select those in the multipollutant model.
Table 2
Spearman’s correlation coefficients between daily COPD mortality, PM pollutants, and weather conditions in Zhejiang Province, 2014–2016
Variable | COPD (death/day) | PM2.5 (µg/m3) | PM2.5-10 (µg/m3) | PM10 (µg/m3) | Temperature (℃) | Pressure (hpa) | Relative humidity (%) | Wind speed (m/s) | Precipitation (mm) |
COPD (death/day) | 1 | | | | | | | | |
PM2.5 (µg/m3) | 0.302** | 1 | | | | | | | |
PM2.5-10 (µg/m3) | 0.282** | 0.523** | 1 | | | | | | |
PM10 (µg/m3) | 0.323** | 0.933** | 0.772** | 1 | | | | | |
Temperature (℃) | -0.163** | -0.345** | -0.170** | -0.333** | 1 | | | | |
Pressure (hpa) | 0.161** | 0.294** | 0.289** | 0.342** | -0.869** | 1 | | | |
Relative humidity (%) | -0.0683** | -0.309** | -0.471** | -0.423** | 0.109** | -0.216** | 1 | | |
Wind speed (m/s) | 0.308** | -0.159** | -0.010 | -0.111** | -0.0486** | 0.114** | -0.122** | 1 | |
Precipitation (mm) | 0.0256 | -0.247** | -0.408** | -0.348** | -0.0157 | -0.147** | 0.637** | 0.030 | 1 |
** P < 0.01 |
Table 3 and Fig. 2 show the short-term associations between PM pollutants and COPD mortality over different lag days. We observed significant associations between COPD mortality and PM2.5 in lags of 1, 2, 3, 5, 7, 0–1, 0–2, and 0–3 days (ER = 1.03%, 95% CI: 0.361%, 1.70%; ER = 1.09%, 95% CI: 0.427%, 1.75%; ER = 0.868%, 95% CI: 0.214%, 1.53%; ER = 0.671%, 95% CI: 0.015%, 1.33%; ER = 0.751%, 95% CI: 0.096%, 1.41%; ER = 1.10%, 95% CI: 0.299%, 1.91%; ER = 1.55%, 95% CI: 0.668%, 2.44%; and ER = 1.85%, 95% CI: 0.895%, 2.82%, respectively). We also observed a significant association between COPD mortality and PM2.5−10 in lags of 2, 0–2, and 0–3 days (ER = 1.09%, 95% CI: 0.0680%, 2.13%; ER = 1.54%, 95% CI: 0.164%, 2.93%; ER = 1.50%, 95% CI: 0.058%, 2.95%, respectively). We also observed a significant association between COPD mortality and PM10in lags of 1, 2, 3, 5, 0–1, 0–2,and 0–3 days (ER = 0.711%, 95% CI: 0.236%, 1.19%; ER = 0.797%, 95% CI: 0.333%, 1.26%; ER = 0.504%, 95% CI: 0.0440%, 0.966%; ER = 0.495%, 95% CI: 0.0370%, 0.955%; ER = 0.764%, 95% CI: 0.189%, 1.34%; ER = 1.09%, 95% CI: 0.468%, 1.71%;and ER = 1.22%, 95% CI: 0.559%, 1.89%, respectively). Table 4 gives the adjusted effects of PM pollutant on COPD mortality. We found that the effects of PM2.5−10 on COPD mortality were not significant after they were adjusted for PM2.5 in either single or multiple lag models.
Table 3
Excess risk (95% confident intervals) of COPD mortality associated with a 10 µg/m3 increase in PM pollutants along different lags in Zhejiang Province, 2014–2016
Lag | PM2.5 | PM2.5-10 | PM10 |
ER( 95% CI) | P | ER( 95% CI) | P | ER( 95% CI) | P |
0 | 0.566(-0.152-1.29) | 0.123 | 0.518(-0.713-1.76) | 0.411 | 0.399(-0.129-0.930) | 0.139 |
1 | 1.03(0.361-1.70) | 0.002 | 0.815(-0.255-1.90) | 0.136 | 0.711(0.236–1.19) | 0.003 |
2 | 1.09(0.427–1.75) | 0.001 | 1.09(0.0680–2.13) | 0.037 | 0.797(0.333–1.26) | 0.001 |
3 | 0.868(0.214–1.53) | 0.009 | 0.165(-0.851-1.19) | 0.752 | 0.504(0.044–0.97) | 0.032 |
4 | 0.418(-0.237-1.08) | 0.212 | 0.050(-0.957-1.07) | 0.923 | 0.238(-0.220-0.698) | 0.309 |
5 | 0.671(0.0150–1.33) | 0.045 | 0.683(-0.321-1.70) | 0.183 | 0.495(0.037–0.955) | 0.034 |
6 | 0.625(-0.0310-1.29) | 0.062 | 0.072(-0.932-1.09) | 0.889 | 0.331(-0.128-0.792) | 0.158 |
7 | 0.751(0.096–1.41) | 0.025 | -0.091(-1.09-0.92) | 0.860 | 0.345(-0.113-0.805) | 0.140 |
01 | 1.10(0.299–1.91) | 0.007 | 0.992(-0.311-2.31) | 0.136 | 0.764(0.189–1.34) | 0.009 |
02 | 1.55(0.668–2.44) | 0.001 | 1.54(0.164–2.93) | 0.028 | 1.09(0.468–1.71) | 0.001 |
03 | 1.85(0.895–2.82) | 0.000 | 1.50(0.058–2.95) | 0.041 | 1.22(0.559–1.89) | 0.000 |
Table 4
Excess risk (95% confident intervals) of COPD mortality associated with a 10 µg/m3 increase in PM pollutants with multipollutant model in Zhejiang Province, 2014–2016
Pollutants | Lag | ER( 95% CI) | P |
PM2.5(Adjusted PM2.5−10) | 2 | 0.908(0.164–1.66) | 0.017 |
| 03 | 1.71(0.634–2.79) | 0.002 |
PM2.5−10(Adjusted PM2.5) | 2 | 0.604(-0.558-1.78) | 0.310 |
| 02 | 0.482(-1.04-2.02) | 0.536 |
Figure 3 revealed the exposure-response curves for daily concentrations of PM pollutants associated with COPD mortality. According to the AIC values of each lag model, we selected lag 2 for single-day and lag 03 for multiple-day as lag time, except PM2.5−10, in which we selected lag 02 for multiple-day. A visual inspection suggested nonlinear effects on COPD mortality both in PM2.5 and PM10 for lag 2 were more obvious than those for lag03. As shown in Fig. 3, the nonlinear effects on COPD mortality for PM2.5 and PM10 in lag03 and PM2.5−10 in lag2 and lag02 were negligible.