Major air pollutants and risk of COPD exacerbations: a systematic review and meta-analysis

Figures & data

Figure 1 PRISMA flow chart of identified, included, and excluded studies.

Abbreviation: COPD, chronic obstructive pulmonary disease.

Table 1 Contextual details of the studies included in the meta analysis

Study (year)	Location	Design	Period	Outcome	Population	Events	Age	Confounders
Kloog et al^Citation46 (2014)	USA	CC	2000–2006	HA	58.0 million	0.42 million	≥65 yrs	A
Meng et al^Citation47 (2013)	China	TS	1996–2008	Mortality	34.0 million	32.2/day	All	A.B
Tellez-Rojo et al^Citation48 (2000)	Mexico	TS	1994–1995	Both	0.9 million	2,294	≥65 yrs	A.B.C.D.E.F
Wordley et al^Citation49 (1997)	UK	TS	1992–1994	Both	1 million	HA 3.2/day, M 2/day	All	A.B
Neuberger et al^Citation7 (2007)	Austria	TS	1972–1983	Mortality	1.6 million	2,878	≥65 yrs	A.B.E.G.H
Yorifuji et al^Citation50 (2014)	Japan	CC	2006–2010	HA	6,925	761	≥65 yrs	A.B.H
Schikowski et al^Citation51 (2014)	Taiwan	CC	2006–2010	HA	1.5 million	7.7/day	All	A.B.C.E.I
Tao et al^Citation52 (2013)	China	TS	2001–2005	HA	NA	2.0/day	All	A.B.C.G.F
Moolgavkar et al^Citation53 (1997)	Europe	TS	1986–1991	HA	NA	2.6/day	All	A.C.F.I
Hinwood et al^Citation54 (2006)	Australia	CC	1992–1998	HA	1.2 million	3.3/day	All	A.B.C.D
Milutinovic et al^Citation55 (2009)	Serbia	TS	2002–2003	HA	0.17 million	12.5/day	All	A.B.G.J.K.L.M
Arbex et al^Citation56 (2009)	Brazil	TS	2001–2003	HA	11.2 million	1.7/day	≥40 yrs	A.B.C.E.F
Forastiere et al^Citation57 (2008)	Italy	CC	1997–2004	Mortality	0.32 million	19.6/day	≥35 yrs	A.B.C.E.I.H.G.
Ko et al^Citation58 (2007)	Hong Kong	TS	2000–2004	HA	7 million	65.3/day	All	A.B.C.D.E
Zanobetti et al^Citation59 (2000)	USA	TS	1986–1994	HA	1.8 million	22/day	≥65 yrs	A.B
Morgan et al^Citation60 (1998)	Australia	TS	1990–1994	HA	NA	9.7/day	≥65 yrs	A.B.C.D.E
Anderson et al^Citation61 (1997)	Europe	TS	1977–1992	HA	18.2 million	49.2/day	≥65 yrs	A.B.H.E
Peel et al^Citation8 (2005)	USA	TS	1993–2000	HA	4.0 million	7.4/day	All	A.B.C.G.F.D.N
Chen et al^Citation62 (2003)	Canada	TS	2002–2003	HA	NA	4,409	≥65 yrs	A.B.E.F
Wong et al^Citation63 (2002)	Hong Kong	TS	1995–1998	Mortality	8.5 million	6.0/day	All	A.B.C.F
Tenias et al^Citation64 (2002)	Spain	TS	1994–1995	HA	0.8 million	1.8/day	≥14 yrs	A.B.C.D.F.H
Yang et al^Citation10 (2004)	Canada	TS	1994–1998	HA	2.0 million	3.3/day	≥65 yrs	A.B.G.E.O
Qiu et al^Citation65 (2012)	Hong Kong	TS	2000–2005	HA	0.7 million	81.1/day	All	A.B.C.D.E.F.H
Stieb et al^Citation66 (2009)	Canada	TS	1990–2000	HA	4.0 million	40.5/day	All	A.B.C.D.G.O
Wong et al^Citation67 (1999)	Hong Kong	TS	1994–1995	HA	7.0 million	NA	All	A.B.C.D.E.F
Schouten et al^Citation68 (1996)	the Netherlands	TS	1977–1989	HA	0.76 million	1.7/day	All	A.B.C.D.F
Fusco et al^Citation34 (2001)	Rome	TS	1995–1997	HA	3.0 million	13.0/day	All	A.B.C.D.H
Sauerzapf et al^Citation69 (2009)	UK	CC	2006–2007	HA	0.8 million	1,050	≥18 yrs	A.B.H.P
Ramon et al^Citation70 (2005)	USA	CC	1986–1999	HA	NA	578,006	≥65 yrs	A.B.C
Janssen et al^Citation71 (2013)	Europe	TS	2008–2009	Mortality	16.5 million	17.2/day	All	A.B.C.D.F.G.H
Lin et al^Citation72 (2012)	Taiwan	TS	2000–2009	HA	6.0 million	15.0/day	All	A.B.C.D.H.M
Bateson et al^Citation73 (2004)	USA	CC	1988–1991	Mortality	0.06 million	16,403	≥65 yrs	A.B.G
Sunyer et al^Citation74 (2001)	Spain	CC	1985–1995	Mortality	NA	2,305	≥35 yrs	A.B.C.H
Kan et al^Citation75 (2003)	China	CC	2000–2001	Mortality	NA	11.0/day	All	A.B
Braga et al^Citation76 (2001)	USA	TS	1986–1993	Mortality	12.5 million	13.2/day	All	A.B.E.G
Schwartz et al^Citation77 (1992)	USA	TS	1973–1980	Mortality	1.7 million	0.9/day	All	A.B.C.E.O
Fischer et al^Citation78 (2003)	the Netherlands	TS	1986–1994	Mortality	14.8 million	15.0/day	≥65 yrs	A.B.D
Wong et al^Citation79 (2009)	Hong Kong	TS	1996–2000	Both	8.0 million	M 5.9/day, HA 91.5/day	All	B.H
Xu et al^Citation9 (2000)	China	TS	1992–1993	Mortality	3.1 million	6.2/day	All	A.B.D
Janssen et al^Citation80 (2002)	USA	TS	1985–1994	HA	NA	NA	≥65 yrs	A.B.C.D.G
Dominici et al^Citation81 (2006)	USA	TS	1999–2002	HA	11.5 million	26.0/day	≥65 yrs	A
Yang et al^Citation82 (2000)	USA	TS	1990–1994	HA	NA	3,115	All	A.B.C.D.E.F.G
Schwartz et al^Citation83 (1994)	USA	TS	1986–1989	HA	0.9 million	2.0/day	≥65 yrs	A.B.G.E.F
Schwartz(s) et al^Citation44 (1994)	USA	TS	1986–1989	HA	2.5 million	3.0/day	≥65 yrs	A.B.G.F
Schwartz(t) et al^Citation84 (1994)	USA	TS	1986–1989	HA	4.4 million	5.8/day	All	A.B.E.G
Sunyer et al^Citation85 (1993)	Spain	TS	1985–1989	HA	NA	15.8/day	≥45 yrs	A.B.C.O
Lippmann et al^Citation86 (2000)	USA	TS	1982–1994	Both	NA	8.0/day	All	A.B.E.H
Dab et al^Citation87 (1996)	France	TS	1987–1992	Both	6.14 million	12.0/day	All	A.B.C.D.E.H.Q
Leitte et al^Citation88 (2009)	Romania	TS	2001–2002	Both	0.1 million	1.4/day	All	A.B.D.E.H.G.R
Pande et al^Citation89 (2002)	India	TS	1997–1998	HA	NA	22.0/day	All	A.B.E.F
Cirera et al^Citation90 (2011)	UK	TS	1995–1998	HA	0.2 million	2.0/day	All	A.B.C.E.H.G
Yang et al^Citation91 (2007)	Taiwan	CC	1996–2003	HA	2.6 million	15.9/day	All	A.B
Lee et al^Citation92 (2007)	Taiwan	CC	1996–2003	HA	1.5 million	8.6/day	All	A.B
Peacok et al^Citation93 (2010)	UK	TS	1995–1997	HA	NA	94	≥65 yrs	A.B.E
Zhang et al^Citation94 (2013)	China	TS	2008–2011	HA	8.7 million	2,000	All	A.B.F.G
Cho et al^Citation95 (2013)	Korea	CC	2005–2009	HA	4,989	548	≥44 yrs	A.B.S.D
Tian et al^Citation96 (2014)	Hong Kong	TS	2001–2007	HA	8.0 million	57.0/day	All	A.B.C.D
To et al^Citation97 (2015)	Canada	TS	2003–2010	HA	13.0 million	615,540	All	A.C.E.O.T
Cai et al^Citation98 (2015)	China	TS	2006–2008	HA	7.0 million	121,463	All	A.B.E.F

Note: Both= the outcome includes HA and Mortality.

Abbreviations: A, temperature; B, humidity; C, day of week; CC, case-crossover study; D, holiday; E, seasonality; F, long-term trend; G, barometric pressure; H, influenza; HA, hospital admission; I, chronic time trend; J, rainfall; K, precipitation; L, overcast; M, wind velocity; N, hospital entry/exit; NA, not available; O, animal trend; P, pollen; Q, linear effects; R, nonlinear effects, S, sunlight hours; T, socioeconomic status; TS, time-series study; yrs, years old.

Table 2 Subgroup analysis by gaseous and particulate pollutants

	Gaseous pollutants				Particulate pollutants
	Carbon monoxide	Nitrogen dioxide	Sulfur dioxide	Ozone	PM2.5	PM10
Increment	100 μg/m^3	10 μg/m^3	10 μg/m^3	10 μg/m^3	10 μg/m^3	10 μg/m^3
Mean pollutant	1.18	64.56	26.47	54.90	14.84	46.44
Standard deviation	0.38	20.32	10.75	22.87	8.05	29.50
Range (minimum–maximum)	0.40–3.04	10.23–126.40	9.08–59.68	13.19–119.47	5.20–94.59	11.98–135.17
Number of studies	15	29	28	29	14	35
Number of estimates	17	32	32	34	15	38
RR (95% CI)	1.008 (1.004, 1.013)	1.045 (1.028, 1.062)	1.006 (1.001, 1.012)	1.028 (1.011, 1.044)	1.024 (1.005, 1.043)	1.017 (1.012, 1.022)
Heterogeneity, I^2	97.0	98.0	80.8	98.8	97.1	86.2
P-value	<0.001	<0.001	<0.001	<0.001	<0.001	<0.001
PAF, % (95% CI)
k=100%	0.79 (0.40, 1.28)	4.31 (2.72, 5.84)	0.60 (0.00, 1.19)	NA	2.34 (0.50, 4.12)	1.67 (1.19, 2.15)
k=80%	0.64 (0.32, 1.03)	3.47 (2.18, 4.67)	0.48 (0.08, 0.95)	NA	1.88 (0.40, 3.33)	1.34 (0.95, 1.73)
k=20%	0.16 (0.08, 0.26)	0.89 (0.56, 1.22)	0.12 (0.02, 0.24)	NA	0.48 (0.10, 0.85)	0.34 (0.24, 0.44)
Publication bias
Egger regression test, P-value	0.160	0.147	0.007	<0.001	0.447	<0.001
Adjusted estimates (95% CI)	1.002 (1.001, 1.003)	1.021 (1.004, 1.018)	1.004 (0.998, 1.011)	0.976 (0.962, 0.991)	1.006 (1.004, 1.008)	1.008 (1.004, 1.011)

Abbreviations: CI, confidence interval; NA, not available; RR, relative risk; PAF, population attributable fraction.

Figure 2 Associations between gaseous and particular air pollution and COPD risk stratified by time lag (days).

Abbreviations: CI, confidence interval; COPD, chronic obstructive pulmonary disease; RR, relative risk.

Figure 3 Subgroup analysis for all gaseous and particulate air pollutants stratified by outcome, location, age, and study design.

Abbreviations: CI, confidence interval; COPD, chronic obstructive pulmonary disease; RR, relative risk.

Figure 4 Cartogram identifying associations between sulfur dioxide and nitrogen dioxide short-term exposure and COPD risk stratified by countries of high- and low-/middle-income levels.

KloogINordioFZanobettiACoullBAKoutrakisPSchwartzJDShort term effects of particle exposure on hospital admissions in the Mid-Atlantic states: a population estimatePloS One201492e8857824516670

 PubMed Web of Science ®Google Scholar

MengXWangCCaoDWongC-MKanHShort-term effect of ambient air pollution on COPD mortality in four Chinese citiesAtmospheric Environment201377149154

 Web of Science ®Google Scholar

Tellez-RojoMRomieuIRuiz-VelascoSLezanaMHernandez-AvilaMDaily respiratory mortality and PM10 pollution in Mexico City: importance of considering place of deathEuropean Respiratory Journal200016339139611028649

 PubMed Web of Science ®Google Scholar

WordleyJWaltersSAyresJGShort term variations in hospital admissions and mortality and particulate air pollutionOccupational and Environmental Medicine19975421081169072018

 PubMed Web of Science ®Google Scholar

NeubergerMRabczenkoDMoshammerHExtended effects of air pollution on cardiopulmonary mortality in ViennaAtmos Environ2007413885498556

 Web of Science ®Google Scholar

YorifujiTSuzukiEKashimaSHourly differences in air pollution and risk of respiratory disease in the elderly: a time-stratified case-crossover studyEnvironmental Health20141316725115710

 PubMed Web of Science ®Google Scholar

SchikowskiTAdamMMarconAAssociation of ambient air pollution with the prevalence and incidence of COPDEur Respir J201444361462624488569

 PubMed Web of Science ®Google Scholar

TaoYMiSZhouSWangSXieXAir pollution and hospital admissions for respiratory diseases in Lanzhou, ChinaEnvironmental Pollution201418519620124286694

 PubMed Web of Science ®Google Scholar

MoolgavkarSHLuebeckEGAndersonELAir pollution and hospital admissions for respiratory causes in Minneapolis-St. Paul and BirminghamEpidemiology19973643709209848

 PubMed Web of Science ®Google Scholar

HinwoodADe KlerkNRodriguezCThe relationship between changes in daily air pollution and hospitalizations in Perth, Australia 1992–1998: a case-crossover studyInternational Journal of Environmental Health Research2006161274616507479

 PubMed Web of Science ®Google Scholar

MilutinovicSNikicDStosicLStankovicABogdanovicDShort-term association between air pollution and emergency room admissions for chronic obstructive pulmonary disease in Nis, SerbiaCentral European Journal of Public Health2009171819418713

 PubMedGoogle Scholar

ArbexMAde Souza ConceiçãoGMCendonSPUrban air pollution and chronic obstructive pulmonary disease-related emergency department visitsJournal of Epidemiology and Community Health2009631077778319468016

 PubMed Web of Science ®Google Scholar

ForastiereFStafoggiaMBertiGParticulate matter and daily mortality: a case-crossover analysis of individual effect modifiersEpidemiology200819457158018467959

 PubMed Web of Science ®Google Scholar

KoFWTamWWongTWTemporal relationship between air pollutants and hospital admissions for chronic obstructive pulmonary disease in Hong KongThorax200762978078517311838

 PubMed Web of Science ®Google Scholar

ZanobettiASchwartzJDockeryDWAirborne particles are a risk factor for hospital admissions for heart and lung diseaseEnvironmental Health Perspectives200010811107111102299

 PubMed Web of Science ®Google Scholar

MorganGCorbettSWlodarczykJAir pollution and hospital admissions in Sydney, Australia, 1990 to 1994American Journal of Public Health19988812176117669842371

 PubMed Web of Science ®Google Scholar

AndersonHSpixCMedinaSAir pollution and daily admissions for chronic obstructive pulmonary disease in 6 European cities: results from the APHEA projectEuropean Respiratory Journal1997105106410719163648

 PubMed Web of Science ®Google Scholar

PeelJLTolbertPEKleinMAmbient air pollution and respiratory emergency department visitsEpidemiology200516216417415703530

 PubMed Web of Science ®Google Scholar

ChenYYangQKrewskiDShiYBurnettRTMcGrailKInfluence of relatively low level of particulate air pollution on hospitalization for COPD in elderly peopleInhalation Toxicology2004161212514744661

 PubMed Web of Science ®Google Scholar

WongTTamWYuTWongAAssociations between daily mortalities from respiratory and cardiovascular diseases and air pollution in Hong Kong, ChinaOccupational and Environmental Medicine2002591303511836466

 PubMed Web of Science ®Google Scholar

TeniasJMBallesterFPerez-HoyosSRiveraMLAir pollution and hospital emergency room admissions for chronic obstructive pulmonary disease in Valencia, SpainArchives of Environmental Health2002571414712071359

 PubMed Web of Science ®Google Scholar

YangQChenYKrewskiDBurnettRTShiYMcGrailKMEffect of short-term exposure to low levels of gaseous pollutants on chronic obstructive pulmonary disease hospitalizationsEnviron Res20059919910516053934

 PubMed Web of Science ®Google Scholar

QiuHYuIT-sTianLEffects of coarse particulate matter on emergency hospital admissions for respiratory diseases: a time-series analysis in Hong KongEnvironmental Health Perspectives2012120457222266709

 PubMed Web of Science ®Google Scholar

StiebDMSzyszkowiczMRoweBHLeechJAAir pollution and emergency department visits for cardiac and respiratory conditions: a multi-city time-series analysisEnviron Health2009825101186

 Google Scholar

WongTWLauTSYuTSAir pollution and hospital admissions for respiratory and cardiovascular diseases in Hong KongOccupational and Environmental Medicine1999561067968310658547

 PubMed Web of Science ®Google Scholar

SchoutenJVonkJDe GraafAShort term effects of air pollution on emergency hospital admissions for respiratory disease: results of the APHEA project in two major cities in The Netherlands, 1977–89Journal of Epidemiology and Community Health199650Suppl 1s22s298758220

 PubMed Web of Science ®Google Scholar

FuscoDForastiereFMichelozziPAir pollution and hospital admissions for respiratory conditions in Rome, ItalyEur Respir J2001171143115011491157

 PubMed Web of Science ®Google Scholar

SauerzapfVJonesAPCrossJEnvironmental factors and hospitalisation for chronic obstructive pulmonary disease in a rural county of EnglandJournal of Epidemiology and Community Health200963432432819208692

 PubMed Web of Science ®Google Scholar

Medina-RamonMZanobettiASchwartzJThe effect of ozone and PM10 on hospital admissions for pneumonia and chronic obstructive pulmonary disease: A national multicity studyAmerican Journal of Epidemiology2006163657958816443803

 PubMed Web of Science ®Google Scholar

JanssenNFischerPMarraMAmelingCCasseeFShort-term effects of PM 2.5, PM 10 and PM 2.5–10 on daily mortality in the NetherlandsScience of the Total Environment2013463202623787105

 PubMed Web of Science ®Google Scholar

LinYChangSLinCChenYWangYComparing ozone metrics on associations with outpatient visits for respiratory diseases in Taipei Metropolitan areaEnvironmental Pollution201317717718423333210

 PubMed Web of Science ®Google Scholar

BatesonTFSchwartzJWho is sensitive to the effects of particulate air pollution on mortality? A case-crossover analysis of effect modifiersEpidemiology200415214314915127905

 PubMed Web of Science ®Google Scholar

SunyerJSchwartzJTobiasAMacfarlaneDGarciaJAntoJMPatients with chronic obstructive pulmonary disease are at increased risk of death associated with urban particle air pollution: A case-crossover analysisAmerican Journal of Epidemiology20001511505610625173

 PubMed Web of Science ®Google Scholar

KanHChenBAir Pollution and Daily Mortality in Shanghai: A Time-Series StudyArchives of Environmental Health200358636036714992311

 PubMedGoogle Scholar

BragaALFZanobettiASchwartzJThe lag structure between particulate air pollution and respiratory and cardiovascular deaths in 10 US citiesJournal of Occupational and Environmental Medicine2001431192793311725331

 PubMed Web of Science ®Google Scholar

SchwartzJDockeryDWIncreased mortality in Philadelphia associated with daily air pollution concentrationsAmerican Review of Respiratory Disease199214536006041546841

 PubMed Web of Science ®Google Scholar

FischerPHoekGBrunekreefBVerhoeffAVan WijnenJAir pollution and mortality in the Netherlands: are the elderly more at risk?European Respiratory Journal20032140 suppl34s38s

 Web of Science ®Google Scholar

WongPMLeesANLouwJEmphysema in young adult survivors of moderate-to-severe bronchopulmonary dysplasiaEuropean Respiratory Journal200832232132818385172

 PubMed Web of Science ®Google Scholar

XuZYuDJingLXuXAir pollution and daily mortality in Shenyang, ChinaArch Environ Health200055211512010821512

 PubMed Web of Science ®Google Scholar

JanssenNAHSchwartzJZanobettiASuhHHAir conditioning and source-specific particles as modifiers of the effect of PM10 on hospital admissions for heart and lung diseaseEnvironmental Health Perspectives200211014349

 PubMed Web of Science ®Google Scholar

DominiciFPengRDBellMLFine particulate air pollution and hospital admission for cardiovascular and respiratory diseasesJAMA2006295101127113416522832

 PubMed Web of Science ®Google Scholar

YangCYChenCJAir pollution and hospital admissions for chronic obstructive pulmonary disease in a subtropical city: Taipei, TaiwanJournal of Toxicology and Environmental Health Part A: Current Issues2007701412141219

 PubMed Web of Science ®Google Scholar

SchwartzJPM10, ozone, and hospital admissions for the elderly in Minneapolis-St. Paul, MinnesotaArchives of Environmental Health19944953663747944569

 PubMed Web of Science ®Google Scholar

SchwartzJMorrisRAir pollution and hospital admissions for cardiovascular disease in Detroit, MichiganAm J Epidemiol1995142123357785670

 PubMed Web of Science ®Google Scholar

SchwartzJAir pollution and hospital admissions for the elderly in Birmingham, AlabamaAmerican Journal of Epidemiology199413965895988172170

 PubMed Web of Science ®Google Scholar

SunyerJSaezMMurilloCCastellsagueJMartinezFAntoJMAir pollution and emergency room admissions for chronic obstructive pulmonary disease: A 5-year studyAmerican Journal of Epidemiology199313777017058484361

 PubMed Web of Science ®Google Scholar

LippmannMItoKNadasABurnettRAssociation of particulate matter components with daily mortality and morbidity in urban populationsResearch Report (Health Effects Institute)200095572 discussion 73–82

 PubMedGoogle Scholar

DabWMedinaSQuenelPShort term respiratory health effects of ambient air pollution: results of the APHEA project in ParisJournal of Epidemiology and Community Health199650Suppl 1s42s468758223

 PubMed Web of Science ®Google Scholar

LeitteAMPetrescuCFranckURespiratory health, effects of ambient air pollution and its modification by air humidity in Drobeta-Turnu Severin, RomaniaScience of the Total Environment2009407134004401119375151

 PubMed Web of Science ®Google Scholar

PandeJBhattaNBiswasDOutdoor air pollution and emergency room visits at a hospital in DelhiIndian Journal of Chest Diseases and Allied Sciences2002441132011845928

 PubMedGoogle Scholar

CireraLGarcía-MarcosLGiménezJDaily effects of air pollutants and pollen types on asthma and COPD hospital emergency visits in the industrial and Mediterranean Spanish city of CartagenaAllergologia et Immunopathologia201240423123721890258

 PubMed Web of Science ®Google Scholar

YangC-YChenC-JAir pollution and hospital admissions for chronic obstructive pulmonary disease in a subtropical city: Taipei, TaiwanJournal of Toxicology and Environmental Health, Part A200770141214121917573635

 PubMed Web of Science ®Google Scholar

LeeI-MTsaiS-SChangC-CHoC-KYangC-YAir pollution and hospital admissions for chronic obstructive pulmonary disease in a tropical city: Kaohsiung, TaiwanInhalation Toxicology200719539339817365044

 PubMed Web of Science ®Google Scholar

PeacockJLAndersonHRBremnerSAOutdoor air pollution and respiratory health in patients with COPDThorax2011 thx.2010.155358

 Web of Science ®Google Scholar

ZhangZWangJChenLImpact of haze and air pollution-related hazards on hospital admissions in Guangzhou, ChinaEnvironmental Science and Pollution Research20142164236424424306726

 PubMed Web of Science ®Google Scholar

ChoJChoiYJSuhMAir pollution as a risk factor for depressive episode in patients with cardiovascular disease, diabetes mellitus, or asthmaJournal of Affective Disorders2014157455124581827

 PubMed Web of Science ®Google Scholar

TianLHoKFWangTAmbient carbon monoxide and the risk of hospitalization due to chronic obstructive pulmonary diseaseAmerican Journal of Epidemiology11591801211591167

 Google Scholar

ToTFeldmanLSimatovicJHealth risk of air pollution on people living with major chronic diseases: a Canadian population-based studyBMJ Open201559e009075

 PubMed Web of Science ®Google Scholar

CaiJChenRWangWXuXHaSKanHDoes ambient CO have protective effect for COPD patient?Environ Res2015136212625460616

 PubMed Web of Science ®Google Scholar