Abstract
OBJECTIVES: In this study, associations of short-term changes in ambient air pollution with emergency department (ED) visits for asthma were examined in hospitals in the area of Windsor, Ontario. Ambient air pollution quality was represented by the Air Quality Health Index(AQHI), calculated using a formula that combines the concentrations and the relative health impacts of three ambient air pollutants: ozone, nitrogen dioxide and fine particulate matter.
METHODS: Data on ED visits were retrieved from the National Ambulatory Care Reporting System. Only patients two years of age and older were considered. A time-stratified case-crossover design was applied to 6,697 ED visits for asthma for the period of April 2004 to December 2010. Odds ratios (ORs) and their corresponding 95% confidence intervals (CIs) for ED visits associated with increased (by one unit) levels of AQHI were calculated by applying conditional logistic regression.
RESULTS: Positive and statistically significant results were observed between AQHI levels and ED visits for asthma. For all patients the largest value, OR=1.17 (CI: 1.09, 1.26), was obtained for exposures lagged by 9 days in the warm season (April-September). Effects among children 2 to 14 years of age were observed for same-day exposure (lag 0), with an OR=1.11(CI: 1.01, 1.21).
CONCLUSION: Exposure to ambient air pollution in Windsor increases the risk of ED visits for asthma. When the adverse effects of air pollutants are increased, patient visits to the ED depend on the patient’s age.
Keywords: Air pollution, air quality health index, asthma, emergency department
Résumé
OBJECTIFS: Dans cette étude, nous avons examiné les associations entre les changements à court terme dans la pollution atmosphérique et les visites aux urgences dues à l’asthme dans les hôpitaux de la région de Windsor (Ontario). La qualité de l’air ambiant a été représentée par la cote air santé (CAS), calculée selon une formule combinant les concentrations et les effets sanitaires relatifs de trois polluants atmosphériques: l’ozone, le dioxyde d’azote et les particules fines.
MÉTHODE: Les données sur les visites aux urgences ont été extraites du Système national d’information sur les soins ambulatoires. Seuls les patients âgés de deux ans et plus ont été pris en compte. Nous avons appliqué un schéma « case-crossover » stratifié dans le temps à 6 697 visites aux urgences dues à l’asthme pour la période d’avril 2004 à décembre 2010. Nous avons appliqué une régression logistique conditionnelle pour calculer les rapports de cotes (RC) et leurs intervalles de confiance (IC) à 95 % correspondants pour les visites aux urgences associées à des niveaux accrus (d’une unité) de la CAS.
RÉSULTATS: Des résultats positifs et significatifs ont été observés entre les niveaux de la CAS et les visites aux urgences dues à l’asthme. Pour l’ensemble des patients, la plus grande valeur, RC=1,17 (IC: 1,09, 1,26), a été obtenue pour les expositions décalées de 9 jours durant la saison chaude (avril-septembre). Des effets chez les enfants de 2 à 14 ans ont été observés pour les expositions le jour même (0 décalage), avec un RC=1,11 (IC: 1,01, 1,21).
CONCLUSION: L’exposition à la pollution atmosphérique à Windsor accroît le risque de visites aux urgences dues à l’asthme. Quand les effets indésirables des polluants atmosphériques augmentent, les visites aux urgences varient selon l’âge des patients.
Motsclés: pollution de l’air, cote air santé, asthme, service urgences
Footnotes
Acknowledgement: The authors appreciate the efforts of Health Canada in maintaining the National Ambulatory Care Reporting System database. In addition, the authors acknowledge Environment Canada for providing the air pollution data from the National Air Pollution Surveillance Network, for use in this study.
Conflict of Interes: None to declare.
References
- 1.Stieb DM, Burnett RT, Beveridge RC, Brook JR. Association between ozone and asthma emergency department visits in Saint John, New Brunswick, Canada. Environ Health Perspect. 1996;104(12):1354–60. doi: 10.1289/ehp.961041354. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Villeneuve PJ, Chen L, Rowe BH, Coates F. Outdoor air pollution and emergency department visits for asthma among children and adults: A case-crossover study in northern Alberta, Canada. Environ Health. 2007;6:40. doi: 10.1186/1476-069X-6-40. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3.Szyszkowicz M. Ambient air pollution and daily emergency department visits for asthma in Edmonton, Canada. Int J Occup Med Environ Health. 2008;21(1):25–30. doi: 10.2478/v10001-008-0002-3. [DOI] [PubMed] [Google Scholar]
- 4.Gasana J, Dillikar D, Mendy A, Forno E, Ramos Vieira E. Environ Res. 2012. Motor vehicle air pollution and asthma in children: A meta-analysis. [DOI] [PubMed] [Google Scholar]
- 5.The Weather Network. Air Quality: Air Quality Summary. 2010. [Google Scholar]
- 6.Goal A: Improve our air and water quality. http://www.citywindsor.ca/residents/environment/Environmental-Master-Plan/Pages/State-of-the-Environment.aspx (Accessed July 9, 2012).
- 7.Wang SV, Coull BA, Schwartz J, Mittleman MA, Wellenius GA. Potential for bias in case-crossover studies with shared exposures analyzed using SAS. Am J Epidemiol. 2011;174(1):118–24. doi: 10.1093/aje/kwr038. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 8.Canadian Institute for Health Information. National Ambulatory Care Reporting System (NACRS) 2010. [Google Scholar]
- 9.Stieb DM, Burnett RT, Smith-Doiron M, Brion O, Shin HH, Economou V. A new multipollutant, no-threshold air quality health index based on short-term associations observed in daily time-series analyses. J Air Waste Manag Assoc. 2008;58(3):435–50. doi: 10.3155/1047-3289.58.3.435. [DOI] [PubMed] [Google Scholar]
- 10.Maclure M. The case-crossover design: A method for studying transient effects on the risk of acute events. Am J Epidemiol. 1991;133(2):144–53. doi: 10.1093/oxfordjournals.aje.a115853. [DOI] [PubMed] [Google Scholar]
- 11.Janes H, Sheppard L, Lumley T. Case-crossover analyses of air pollution exposure data: Referent selection strategies and their implications for bias. Epidemiology. 2005;16(6):717–26. doi: 10.1097/01.ede.0000181315.18836.9d. [DOI] [PubMed] [Google Scholar]
- 12.Gasparrini A. Distributed lag linear and non-linear models in R: The package dlnm. J Stat Softw. 2011;43(8):1–20. doi: 10.18637/jss.v043.i08. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 13.Abelsohn A, Stieb DM. Health effects of outdoor air pollution: Approach to counseling patients using the Air Quality Health Index. Can Fam Physician. 2011;57(8):881–87. [PMC free article] [PubMed] [Google Scholar]
- 14.Peel JL, Flanders WD, Todd K, Mulholland JA, Ryan PB, Frumkin H. Ambient air pollution and respiratory emergency department visits. Epidemiology. 2005;16(2):164–74. doi: 10.1097/01.ede.0000152905.42113.db. [DOI] [PubMed] [Google Scholar]
- 15.To T, Shen S, Atenafu EG, Guan J, McLimont S, Stocks B, Licskai C. Environ Health Perspect. 2012. The Air Quality Health Index and asthma morbidity: A population-based study. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 16.Delfino RJ, Murphy-Moulton AM, Burnett RT, Brook JR, Becklake MR. Effects of air pollution on emergency room visits for respiratory illnesses in Montreal, Quebec. Am J Respir Crit Care Med. 1997;155:568–76. doi: 10.1164/ajrccm.155.2.9032196. [DOI] [PubMed] [Google Scholar]
- 17.Burnett RT, Dales RE, Raizenne ME, Krewski D, Summers PW, Roberts GR, et al. Effects of low ambient levels of ozone and sulfate on the frequency of respiratory admissions to Ontario hospitals. Environ Res. 1994;65:172–94. doi: 10.1006/enrs.1994.1030. [DOI] [PubMed] [Google Scholar]
- 18.Burnett RT, Cakmak S, Brook JR, Krewski D. The role of particulate size and chemistry in the association between summertime ambient air pollution and hospitalization for cardiorespiratory diseases. Environ Health Perspect. 1997;105:614–20. doi: 10.1289/ehp.97105614. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 19.Kousha T, Rowe BH. Ambient ozone and emergency department visits due to lower respiratory condition. Int J Occup Med Environ Health. 2014;27(1):50–59. doi: 10.2478/s13382-014-0229-0. [DOI] [PubMed] [Google Scholar]
- 20.Lavigne E, Villeneuve PJ, Cakmak S. Air pollution and emergency department visits for asthma in Windsor. Can J Public Health. 2012;103(1):4–8. doi: 10.1007/BF03404060. [DOI] [PMC free article] [PubMed] [Google Scholar]