Canadian Journal of Public Health

, Volume 102, Issue 1, pp 35–41 | Cite as

The Population Attributable Fraction of Asthma Among Canadian Children

  • Elinor SimonsEmail author
  • Teresa To
  • Sharon Dell
Systematic Review



We calculated the population attributable fraction (PAF) of Canadian childhood asthma due to modifiable environmental exposures, in order to estimate their relative contributions to asthma development based on the current literature.


We conducted a systematic review to determine Canadian childhood asthma incidence, Canadian prevalence of exposure to airborne pollutants and indoor allergens, and international estimates of the risk of developing physician-diagnosed asthma (PDA) associated with each exposure. Combining risk estimates by meta-analysis where possible, PAF was calculated by the formula: \(\frac{{PAF = Attributable\,risk\,*\,Exposure\,prevalence\,*\,100\% }}{{Asthma\,incidence}}\)


Age-specific Canadian childhood asthma incidence ranged from 2.8%-6.9%. Canadian exposure prevalences were: PM10 16%, PM2.5 7.1%, NO2 25%, environmental tobacco smoke (ETS) 9.0%, cat 22%, dog 12%, mouse 17%, cockroach 9.8%, dust mite 30%, moisture 14% and mould 33%. Relative risk estimates of PDA were: PM10 1.64, PM2.5 1.44, NO2 1.29, ETS 1.40, mouse 1.23, cockroach 1.96, and spanned 1.00 for cat, dog, dust mites, moisture and mould. PAF estimates for incident asthma among preschool children were: PM10 11%, PM2.5 1.6%, NO2 4.0%, ETS 2.9%, mouse 6.5% and cockroach 13%.


This systematic review suggests contributions to childhood asthma development from exposure to particulates, NO2, ETS, mouse and cockroach. The associations appeared to be more complex for cat, dog and dust mite allergens and more variable for mould and moisture. Additional prospective, population-based studies of childhood asthma development with objectively-measured exposures are needed to further quantify these associations.

Key words

Asthma children population attributable fraction environmental exposure 



Nous avons calculé la fraction attribuable dans la population (FAP) du risque d’asthme chez les enfants au Canada dû aux expositions environnementales modifiables, afin d’estimer la contribution relative de ces expositions au développement de l’asthme, d’après les publications actuelles.


Nous avons effectué un examen systématique pour déterminer l’incidence de l’asthme chez les enfants au Canada, la prévalence de l’exposition aux polluants atmosphériques et aux allergènes intérieurs au Canada et les estimations internationales du risque de contracter l’asthme diagnostiqué par un médecin (ADM) associées à chaque forme d’exposition. En combinant les estimations du risque par méta-analyse là où il était possible de le faire, nous avons calculé la FAP selon la formule suivante:
$$\frac{{FAP = Risque\,attribuable*\Pr \'e valence\,de\,l\exp osition*100\% }}{<Subscript>cidence\,de\,lasthme</Subscript>}$$


L’incidence par âge de l’asthme chez les enfants au Canada se situait entre 2,8 et 6,9 %. Les taux de prévalence des expositions au Canada étaient les suivants: PM10 16 %; PM2.5 7,1 %; NO2 25 %; fumée secondaire du tabac (FST) 9 %; chats 22 %; chiens 12 %; souris 17 %; blattes 9,8 %; acariens 30 %; humidité 14 %; et moisissures 33 %. Les estimations du risque relatif d’ADM étaient les suivantes: PM10 1,64; PM2.5 1,44; NO2 1,29; FST 1,40; souris 1,23; blattes 1,96; avec une plage de 1,00 pour les chats, les chiens, les acariens, l’humidité et les moisissures. Les estimations de la FAP relativement aux nouveaux cas d’asthme chez les enfants d’âge préscolaire étaient les suivantes: PM10 11 %; PM2.5 1,6 %; NO2 4 %; FST 2,9 %, souris 6,5 %; et blattes 13 %.


Selon cet examen systématique, l’exposition aux matières particulaires, au dioxyde d’azote, à la FST, aux souris et aux blattes contribue au développement de l’asthme chez les enfants. Les associations observées semblent plus complexes pour ce qui est des allergènes des chats, des chiens et des acariens et plus variables en ce qui a trait aux moisissures et à l’humidité. Il faudrait mener d’autres études prospectives en population sur le développement de l’asthme chez les enfants, avec des expositions objectivement mesurées, pour mieux chiffrer ces associations.

Mots clés

asthme enfant fraction attribuable dans la population exposition environnementale 


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  1. 1.
    Midodzi WK, Rowe BH, Majaesic CM, Senthilselvan A. Reduced risk of physiciandiagnosed asthma among children dwelling in a farming environment. Respirology 2007;12(5):692–99.CrossRefGoogle Scholar
  2. 2.
    Chen Y, Dales R, Tang M, Krewski D. Sex-related interactive effect of smoking and household pets on asthma incidence. Eur Respir J 2002;20(5):1162–66.CrossRefGoogle Scholar
  3. 3.
    Marra F, Marra CA, Richardson K, Lynd LD, Kozyrskyj A, Patrick DM, et al. Antibiotic use in children is associated with increased risk of asthma. Pediatrics 2009;123(3):1003–10.CrossRefGoogle Scholar
  4. 4.
    Dik N, Tate RB, Manfreda J, Anthonisen, NR. Risk of physician-diagnosed asthma in the first 6 years of life. Chest 2004;126(4):1147–53.CrossRefGoogle Scholar
  5. 5.
    WHO Air Quality Guidelines for Particulate Matter, Ozone, Nitrogen Dioxide and Sulfur Dioxide, Global Update 2005. Available at: (Accessed January 27, 2009).
  6. 6.
    Environment Canada: Government of Canada 5-year Progress Report–Canada-wide Standards for Particulate Matter and Ozone 2005. Available at: (Accessed January 28, 2009).
  7. 7.
    Canadian Tobacco Use Survey: Summary of Annual Results for 2006. Available at: (Accessed January 20, 2009).
  8. 8.
    Fletcher RW, Fletcher, SW. Clinical Epidemiology: The Essentials, Fourth Edition. Baltimore, MD: Lippincott Williams & Wilkins, 2005.Google Scholar
  9. 9.
    Rockhill B, Newman B, Weinberg C. Use and misuse of population attributable fractions. Am J Public Health 1998;88(1):15–19.CrossRefGoogle Scholar
  10. 10.
    Knol MJ, Vandenbroucke JP, Scott P, Egger M. What do case-control studies estimate? Survey of methods and assumptions in published case-control research. Am J Epidemiol 2008;168(9):1073–81.CrossRefGoogle Scholar
  11. 11.
    DerSimonian R, Laird N. Meta-analysis in clinical trials. Controlled Clinical Trials 1986;7(3):177–88.CrossRefGoogle Scholar
  12. 12.
    Thai A, McKendry I, Brauer M. Particulate matter exposure along designated bicycle routes in Vancouver, British Columbia. Sci Total Environ 2008;405(1-3):26–35.CrossRefGoogle Scholar
  13. 13.
    Johnson D, Mignacca D, Herod D, Jutzi D, Miller H. Characterization and identification of trends in average ambient ozone and fine particulate matter levels through trajectory cluster analysis in eastern Canada. J Air Waste Manag Assoc 2007;57(8):907–18.CrossRefGoogle Scholar
  14. 14.
    Brauer M, Lencar C, Tamburic L, Koehoorn M, Demers P, Karr C. A cohort study of traffic-related air pollution impacts on birth outcomes. Environ Health Perspect 2008;116(5):680–86.CrossRefGoogle Scholar
  15. 15.
    Henderson SB, Beckerman B, Jerrett M, Brauer M. Application of land use regression to estimate long-term concentrations of traffic-related nitrogen oxides and fine particulate matter. Environ Sci Technol 2007;41(7):2422–28.CrossRefGoogle Scholar
  16. 16.
    Larson T, Su J, Baribeau A-M, Buzzelli M, Setton E, Brauer M. A spatial model of urban winter woodsmoke concentrations. Environ Sci Technol 2007;41(7):2429–36.CrossRefGoogle Scholar
  17. 17.
    Villeneuve PJ, Chen L, Rowe BH, Coates F. Outdoor air pollution and emergency department visits for asthma among children and adults: A casecrossover study in northern Alberta, Canada. Environ Health 2007;6:40.CrossRefGoogle Scholar
  18. 18.
    Stieb DM, Evans GJ, Sabaliauskas K, Chen LI, Campbell ME, Wheeler AJ, et al. A scripted activity study of the impact of protective advice on personal exposure to ultra-fine and fine particulate matter and volatile organic compounds. J Expos Sci Environ Epidemiol 2008;18(5):495–502.CrossRefGoogle Scholar
  19. 19.
    Gilbert NL, Goldberg MS, Beckerman B, Brook JR, Jerrett M. Assessing spatial variability of ambient nitrogen dioxide in Montreal, Canada, with a land-use regression model. J Air Waste Manag Assoc 2005;55(8):1059–63.CrossRefGoogle Scholar
  20. 20.
    Brook JR, Poirot RL, Dann TF, Lee PKH, Lillyman CD, Ip T. Assessing sources of PM2.5 in cities influenced by regional transport. J Toxicol Environ Health A 2007;70(3-4):191–99.CrossRefGoogle Scholar
  21. 21.
    Loo CKJ, Foty RG, Wheeler AJ, Miller JD, Evans G, Stieb DM, Dell, SD. Do questions from a questionnaire reflecting indoor air pollutant exposure predict direct measure of exposure in owner-occupied houses? Int J Environ Res Public Health 2010;7(8):3270–97.CrossRefGoogle Scholar
  22. 22.
    Dell SD, Foty RG, Gilbert N, Jerrett M, To T, Walter SD, et al. Asthma and allergic disease prevalence in a diverse sample of Toronto school children: Results from the Toronto Child Health Evaluation Questionnaire (T-CHEQ) Study. Can Respir J 2010;17(1):e1–e6.CrossRefGoogle Scholar
  23. 23.
    Miller JD, Dugandzic R, Frescura A-M, Salares V. Indoor- and outdoor-derived contaminants in urban and rural homes in Ottawa, Ontario, Canada. J Air Waste Manag Assoc 2007;57(3):297–302.CrossRefGoogle Scholar
  24. 24.
    Gilbert NL, Gauvin D, Guay M, Heroux M-E, Dupuis G, Legris M, et al. Housing characteristics and indoor concentrations of nitrogen dioxide and formaldehyde in Quebec City, Canada. Environ Res 2006;102(1):1–8.CrossRefGoogle Scholar
  25. 25.
    Sahsuvaroglu T, Arain A, Kanaroglou P, Finkelstein N, Newbold B, Jerrett M, et al. A land use regression model for predicting ambient concentrations of nitrogen dioxide in Hamilton, Ontario, Canada. J Air Waste Manag Assoc 2006;56(8):1059–69.CrossRefGoogle Scholar
  26. 26.
    Chan-Yeung M, Ferguson A, Watson W, Dimich-Ward H, Rousseau R, Lilley M, et al. The Canadian Childhood Asthma Primary Prevention Study: Outcomes at 7 years of age. J Allergy Clin Immunol 2005;116(1):49–55.CrossRefGoogle Scholar
  27. 27.
    Nordling E, Berglind N, Melen E, Emenius G, Hallberg J, Nyberg F, et al. Trafficrelated air pollution and childhood respiratory symptoms, function and allergies. Epidemiology 2008;19(3):401–8.CrossRefGoogle Scholar
  28. 28.
    Morgenstern V, Zutavern A, Cyrys J, Brockow I, Koletzko S, Kramer U, et al. Atopic diseases, allergic sensitization, and exposure to traffic-related air pollution in children. Am J Respir Crit Care Med 2008;177(12):1331–37.CrossRefGoogle Scholar
  29. 29.
    Brauer M, Hoek G, Smit HA, de Jongste JC, Gerritsen J, Postma DS, et al. Air pollution and development of asthma, allergy and infections in a birth cohort. Eur Respir J 2007;29(5):879–88.CrossRefGoogle Scholar
  30. 30.
    Gehring U, Wijga AH, Brauer M, Fischer P, de Jongste JC, Kerkhof M, et al. Traffic-related air pollution and the development of asthma and allergies during the first 8 years of life. Am J Respir Crit Care Med 2010;181(6):596–603.CrossRefGoogle Scholar
  31. 31.
    Balemans WAF, van der Ent CK, Schilder AGM, Sanders EAM, Zielhuis GA, Rovers, MM. Prediction of asthma in young adults using childhood characteristics: Development of a prediction rule. J Clin Epidemiol 2006;59(11):1207–12.CrossRefGoogle Scholar
  32. 32.
    Jaakkola JJK, Gissler M. Maternal smoking in pregnancy, fetal development, and childhood asthma. Am J Public Health 2004;94(1):136–40.CrossRefGoogle Scholar
  33. 33.
    Ronmark E, Perzanowski M, Platts-Mills T, Lundback B. Incidence rates and risk factors for asthma among school children: A 2-year follow-up report from the obstructive lung disease in Northern Sweden (OLIN) studies. Respir Med 2002;96(12):1006–13.CrossRefGoogle Scholar
  34. 34.
    Strachan DP, Cook, DG. Health effects of passive smoking. 6. Parental smoking and childhood asthma: Longitudinal and case-control studies. Thorax 1998;53(3):204–12.CrossRefGoogle Scholar
  35. 35.
    Lewis S, Richards D, Bynner J, Butler N, Britton J. Prospective study of risk factors for early and persistent wheezing in childhood. Eur Respir J 1995;8(3):349–56.CrossRefGoogle Scholar
  36. 36.
    Martel M-J, Rey E, Malo J-L, Perreault S, Beauchesne M-F, Forget A, et al. Determinants of the incidence of childhood asthma: A two-stage case-control study. Am J Epidemiol 2009;169(2):195–205.CrossRefGoogle Scholar
  37. 37.
    Phipatanakul W, Celedon JC, Sredl DL, Weiss ST, Gold, DR. Mouse exposure and wheeze in the first year of life. Ann Allergy Asthma Immunol 2005;94(5):593–99.CrossRefGoogle Scholar
  38. 38.
    Jaakkola JJK, Hwang B-F, Jaakkola N. Home dampness and molds, parental atopy, and asthma in childhood: A six-year population-based cohort study. Environ Health Perspect 2005;113(3):357–61.CrossRefGoogle Scholar
  39. 39.
    Perzanowski MS, Ronmark E, Platts-Mills TAE, Lundback B. Effect of cat and dog ownership on sensitization and development of asthma among preteenage children. Am J Respir Crit Care Med 2002;166(5):696–702.CrossRefGoogle Scholar
  40. 40.
    Korppi M, Hyvarinen M, Kotaniemi-Syrjanen A, Piippo-Savolainen E, Reijonen T. Early exposure and sensitization to cat and dog: Different effects on asthma risk after wheezing in infancy. Pediatr Allergy Immunol 2008;19:696–701.CrossRefGoogle Scholar
  41. 41.
    Brussee JE, Smit HA, van Strien RT, Corver K, Kerkhof M, Wijga AH, et al. Allergen exposure in infancy and the development of sensitization, wheeze, and asthma at 4 years. J Allergy Clin Immunol 2005;115(5):946–52.CrossRefGoogle Scholar
  42. 42.
    Almqvist C, Egmar AC, Hedlin G, Lundqvist M, Nordvall SL, Pershagen G, et al. Direct and indirect exposure to pets - risk of sensitization and asthma at 4 years in a birth cohort. Clin Exp Allergy 2003;33(9):1190–97.CrossRefGoogle Scholar
  43. 43.
    Celedon JC, Litonjua AA, Ryan L, Platts-Mills T, Weiss ST, Gold, DR. Exposure to cat allergen, maternal history of asthma, and wheezing in first 5 years of life. Lancet 2002;360(9335):781–82.CrossRefGoogle Scholar
  44. 44.
    Sears MR, Greene JM, Willan AR, Taylor DR, Flannery EM, Cowan JO, et al. Long-term relation between breastfeeding and development of atopy and asthma in children and young adults: A longitudinal study. Lancet 2002;360(9337):901–7.CrossRefGoogle Scholar
  45. 45.
    Lau S, Illi S, Sommerfeld C, Niggemann B, Bergmann R, von Mutius E, et al. Early exposure to house-dust mite and cat allergens and development of childhood asthma: A cohort study. Multicentre Allergy Study Group. Lancet 2000;356(9239):1392–97.CrossRefGoogle Scholar
  46. 46.
    Tovey ER, Almqvist C, Li Q, Crisafulli D, Marks, GB. Nonlinear relationship of mite allergen exposure to mite sensitization and asthma in a birth cohort. J Allergy Clin Immunol 2008;122(1):114–18.CrossRefGoogle Scholar
  47. 47.
    Cole Johnson C, Ownby DR, Havstad SL, Peterson, EL. Family history, dust mite exposure in early childhood, and risk for pediatric atopy and asthma. J Allergy Clin Immunol 2004;114(1):105–10.CrossRefGoogle Scholar
  48. 48.
    Lau S, Illi S, Platts-Mills TAE, Riposo D, Nickel R, Gruber C, et al. Longitudinal study on the relationship between cat allergen and endotoxin exposure, sensitization, cat-specific IgG and development of asthma in childhood—report of the German Multicentre Allergy Study (MAS 90). Allergy 2005;60(6):766–73.CrossRefGoogle Scholar
  49. 49.
    Martinez FD, Wright AL, Taussig LM, Holberg CJ, Halonen M, Morgan, WJ. Asthma and wheezing in the first six years of life. The Group Health Medical Associates. N Engl J Med 1995;332(3):133–38.CrossRefGoogle Scholar
  50. 50.
    Phipatanakul W, Celedon JC, Hoffman EB, Abdulkerim H, Ryan LM, Gold, DR. Mouse allergen exposure, wheeze and atopy in the first seven years of life. Allergy 2008;63(11):1512–18.CrossRefGoogle Scholar
  51. 51.
    The Canadian CHILD Study. Available at: (Accessed May 28, 2009).

Copyright information

© The Canadian Public Health Association 2011

Authors and Affiliations

  1. 1.The Hospital for Sick Children Research InstituteChild Health Evaluative SciencesTorontoCanada
  2. 2.Respiratory MedicineThe Hospital for Sick ChildrenTorontoCanada

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