Figure 1Selection process of the relevant studies for meta-analysis. PM10, particulate matter less than 10 µm in aerodynamic diameter.
Figure 2Forest plot of the studies used in the meta-analysis of particulate matter less than 10 µm in aerodynamic diameter exposure and non-accidental mortality: (A) 10 studies for both time-series and case-crossover studies combined; (B) The 8 time-series and 4 case-crossover studies, separated and combined. RR, relative risk; CI, confidence interval.
Figure 3Funnel plot of all 12 of the studies in the meta-analysis.
Table 1.Description of the time-series and case-crossover studies used in the analysis
No |
Author |
City |
Period |
Longitude & lattitude |
Population in millions1 (sample population) |
Daily PM10 (mean±SD [median] μg/m3) |
Daily nonaccidental mortality (mean±SD [median]) |
Lag (matched interval) |
Covariates |
% change per 10 μg/m3 increase of PM10(95% CI) |
Reference |
Time-series analysis |
1 |
Qian et al. (2007) |
Wuhan |
2000. 7-2004. 6 |
114˚16’E, 30˚35’N |
7.8 |
141.8±na (na) |
61±15.78 (59) |
0-1 |
DOW, time trend, extreme cold, hot & humid weather, temperature, humidity |
0.36 (0.19, 0.53) |
15
|
2 |
Kan et al. (2007) |
Shanghai |
2004. 3-2005. 12 |
121˚24’E, 31˚0’N |
17.8 (6.3) |
107.9±2.39 (93.5) |
119±0.87 (115) |
0-1 |
DOW, calendar time, temperature, humidity, ozone |
0.16 (0.02, 0.30) |
16
|
3 |
Bae et al. (2009) |
Seoul |
1999. 1-2004. 12 |
126˚58’E, 37˚33’N |
10.29 |
64.81±30.1 (61.51) |
94±12.18 (93) |
1 |
DOW, time trend, seasonality, temperature, humidity, pressure |
0.37 (0.23, 0.52) |
17
|
4 |
Hong et al. (1999) |
Inchon |
1995. 1-1996. 8 |
126˚42’E, 37˚27’N |
2.4 |
71.2±34.3 (na) |
22.1±4.9 (na) |
1 |
Time trend, seasonality, temperature, humidity |
0.7 (0.11, 1.30) |
18
|
5 |
Wong et al. (2008) |
Hong Kong |
1996. 1-2002. 12 |
114˚6’E, 22˚23’N |
6.74 (6.64) |
51.6±25.3 (45.5) |
84.2±na (na) |
1 |
DOW, time trend, seasonality, holidays, temperature, humidity |
0.4 (0.15, 0.64) |
19
|
6 |
Vichit-Vadakan et al. (2008) |
Bangkok |
1999-2003 |
100˚31’E, 13˚45’N |
6.6 |
52.1±20.1 (46.8) |
95±12.1 (na) |
0-1 |
DOW, time trend, temperature, humidity |
1.3 (0.8, 1.7) |
20
|
7 |
Yu et al. (2012) |
Guangzhou |
2006. 1-2009. 12 |
113˚15’E, 23˚7’N |
11.512 (1.88) |
59.49±24.25 (57.33) |
32.88±7.83 (32) |
0-1 |
DOW, time trend, temperature, humidity |
1.26 (0.86, 1.66) |
14
|
8 |
Li et al. (2012) |
Tianjin |
2006. 1-2009. 10 |
117˚2’E, 39˚1’N |
12.28 (6.0) |
99.7±57.9 (na) |
92.8±21.9 (na) |
0-1 |
DOW, time trend, holidays, temperature, humidity |
0.42 (0.26, 0.58) |
21
|
Case-crossover analysis |
9 |
Kan et al. (2003) |
Shanghai |
2000. 6-2001. 12 |
121˚24’E, 31˚0’N |
13.3 (na) |
91.14±51.85 (76) |
112.02±21.08 (108) |
0-1 (±7, 14, 21 d) |
48 h temperature, 24 h humidity & dewpoint |
0.30 (0.10, 2.50) |
22
|
10 |
Chen et al. (2010) |
Anshan, China |
2004. 1-2006.12 |
122˚59’E, 41˚6’N |
3.483 (1.46) |
110.9±60.2 (98) |
27.6±6.1 (27) |
0-1 (in same month) |
DOW, temperature, humidity |
0.67 (0.03, 1.04) |
23
|
11 |
Yi et al. (2009) |
Seoul |
2000-2006 |
126˚58’E, 37˚33’N |
10.36 |
65.06±36.55 (na) |
93.4±na (na) |
1 (in same month) |
DOW, influenza epidemics, holidays, temperature, humidity, air pressure |
0.24 (0.07, 0.40) |
24
|
12 |
Tsai et al. (2003) |
Kaohsiung |
1994-2000 |
120˚39’E, 23˚0’N |
1.46 |
81.45±na (79.2) |
13.8±na (14) |
0-2 (±7 d) |
Time trend, seasonality, temperature, humidity |
0 (-5.3, 5.6) |
25
|
Table 2.Meta-analysis results for the selected studies
Study groups |
Study number |
Summary estimate (RR [95% CI]) |
I2 (%) |
χ2
|
χ2 p-value |
Eggers p-value |
Studies from each city |
10 |
1.0047 (1.0033, 1.0062) |
63.01 |
28.2615 |
<0.001 |
0.15 |
Time-series studies only |
8 |
1.0057 (1.0029, 1.0085) |
92.43 |
32.4486 |
<0.001 |
na |
Case-crossover studies only |
4 |
1.0027 (1.0010, 1.0043) |
15.09 |
1.6214 |
0.65 |
na |
All selected studies |
12 |
1.0044 (1.0032, 1.0055) |
54.83 |
33.7341 |
<0.001 |
0.08 |