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32ehp
ENVIRONMENTAL
HEALTH
PERSPECTIVES
http://www.ehponline.org
Perinatal Exposure to Traffic-Related Air Pollution and
Atopy at 1 Year of Age in a Multi-Center
Canadian Birth Cohort Study
Hind Sbihi, Ryan W. Allen, Allan Becker, Jeffrey R. Brook,
Piush Mandhane, James A. Scott, Malcolm R. Sears,
Padmaja Subbarao, Tim K. Takaro, Stuart E. Turvey,
and Michael Brauer
http://dx.doi.org/10.1289/ehp.1408700
Received: 15 May 2014
Accepted: 26 March 2015
Advance Publication: 31 March 2015
This article will be available in its final, 508-conformant form 2–4 months
after Advance Publication. If you need assistance accessing this article before
then, please contact ehp508@niehs.nih.gov. Our staff will work with you to
assess and meet your accessibility needs within 3 working days.
ehp
ENVIRONMENTAL
HEALTH
PERSPECTIVES
http://www.ehponline.org
Perinatal Exposure to Traffic-Related Air Pollution and
Atopy at 1 Year of Age in a Multi-Center
Canadian Birth Cohort Study
Hind Sbihi, Ryan W. Allen, Allan Becker, Jeffrey R. Brook,
Piush Mandhane, James A. Scott, Malcolm R. Sears,
Padmaja Subbarao, Tim K. Takaro, Stuart E. Turvey,
and Michael Brauer
http://dx.doi.org/10.1289/ehp.1408700
Received: 15 May 2014
Accepted: 26 March 2015
Advance Publication: 31 March 2015
This article will be available in its final, 508-conformant form 2–4 months
after Advance Publication. If you need assistance accessing this article before
then, please contact ehp508@niehs.nih.gov. Our staff will work with you to
assess and meet your accessibility needs within 3 working days.
Perinatal Exposure to Traffic-Related Air Pollution and Atopy at
1 Year of Age in a Multi-Center Canadian Birth Cohort Study
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Hind Sbihi,
Ryan W. Allen,
Allan Becker,
Jeffrey R. Brook,
Piush Mandhane,
James A.
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Scott,
Malcolm R. Sears,
Padmaja Subbarao,
Tim K. Takaro,
Stuart E. Turvey,
and Michael
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Brauer
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School of Population and Public Health, University of British Columbia, Vancouver, British
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Columbia, Canada;
Faculty of Health Sciences, Simon Fraser University, Burnaby, British
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Columbia, Canada;
Department of Immunology, Faculty of Medicine, University of Manitoba,
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Winnipeg, Manitoba, Canada;
Air Quality Research Division, Environment Canada, Toronto,
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Ontario, Canada;
Department of Pediatrics, Faculty of Medicine and Dentistry, University of
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Alberta, Edmonton, Alberta, Canada;
Dalla Lana School of Public Health, University of
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Toronto, Toronto, Ontario, Canada;
Department of Medicine, Faculty of Health Sciences,
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McMaster University, Hamilton, Ontario, Canada;
Hospital for Sick Children, Department of
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Paediatrics, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada;
BC
Children’s Hospital and Child and Family Research Institute, Department of Paediatrics, Faculty
of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
Address correspondence to Hind Sbihi, School of Population and Public Health, University of
British Columbia, 2206 East Mall, Vancouver BC, V6T 1Z3, Canada. Telephone: (1)604 822-
9608. E-mail:
hind.sbihi@ubc.ca
Running title: Atopy and perinatal exposure to traffic air pollution
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Acknowledgments: The authors extend their gratitude to Diana Lefebvre and Joanne Duncan,
Research Managers for the CHILD study and to members of the CHILD Environmental Working
Group. Thank you to all participating families.
Funding sources: The CHILD Study is funded by the Canadian Institutes of Health Research
(CIHR) and the Allergy, Genes and Environment (AllerGen) Network of Centres of Excellence.
H.S was funded by CIHR Banting and Best doctoral award. S.E. Turvey was supported by a
Clinical Research Scholar Award from the Michael Smith Foundation for Health Research and
the Aubrey J. Tingle Professorship in Pediatric Immunology. M. R. Sears holds the AstraZeneca
endowed Chair in Respiratory Epidemiology.
Competing financial interests: All authors declare no competing financial interests.
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Abstract
Background: The role of traffic related air pollution (TRAP) exposure in the development of
allergic sensitization in children is unclear and few birth cohort studies have incorporated
spatiotemporal exposure assessment.
Objectives: To examine the association between TRAP and atopy in 1 year old children from an
ongoing national birth cohort study in four Canadian cities.
Methods: We identified 2477 children ≥ 1 year old with assessment of atopy for inhalant
(Alternaria, Der p, Der f, Cat, Dog, Cockroach) and food-related (milk, eggs, peanuts, soy)
allergens. Exposure to nitrogen dioxide (NO
) was estimated from city-specific land use
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regression models accounting for residential mobility and temporal variability in ambient
concentrations. We used mixed models to examine associations between atopy and exposure
during pregnancy and the first year of life, including adjustment for covariates (maternal atopy,
SES, pets, mold, and nutrition). We also conducted analyses stratified by time-location patterns,
daycare attendance, and modeled home ventilation.
Results: Following spatiotemporal adjustment, TRAP exposure after birth increased the risk for
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development of atopy to any allergens (adjusted OR per 10 µg/m
NO
= 1.16; 95% CI: 1.00,
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1.41), but not during pregnancy (aOR = 1.02; 95% CI: 0.86, 1.22). This association was stronger
among children not attending daycare (aOR = 1.61; 95% CI: 1.28, 2.01) compared to daycare
attendees (aOR = 1.05; 95% CI: 0.81, 1.28). Trends to increased risk were also found for food
(aOR = 1.17; 95% CI: 0.95, 1.47) and inhalant allergens aOR = 1.28; 95% CI: 0.93, 1.76).
Conclusion: Using refined exposure estimates that incorporated temporal variability and
residential mobility, traffic-related air pollution during the first year of life was associated with
atopy.
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Introduction
The incidence of allergic diseases has increased sharply, especially for people living in urban
areas, which raises an important public health concern given the trend to urbanization worldwide
(D’Amato et al. 2010). While associations between exposure to air pollution derived from traffic
emissions and allergic exacerbations have been demonstrated, the potential role of traffic related
air pollution (TRAP) in the onset of allergic diseases is uncertain (Heinrich and Wichmann
2004).
Several epidemiological studies have reported associations between atopy or other allergic
phenotypes and exposure to some TRAP exposure surrogates, including nitrogen dioxide (NO
)
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(Gruzieva et al. 2012; Janssen et al. 2003; Brauer et al. 2007; Morgenstern et al. 2008).
However, a number of other studies have not observed these positive associations (Gehring et al.
2010; Oftedal et al. 2007). Differences in TRAP exposure assessment approaches are one
possible explanation for these divergent findings.
Despite the importance of early life exposures in the development of allergy, information on the
effect of air pollution exposure, particularly during pregnancy, on allergic responses early in life
has rarely been assessed (Aguilera et al. 2013; Esplugues et al. 2011; Mortimer et al. 2008) and
birth cohort studies addressing this relationship are rare (Bråbäck and Forsberg 2009). Exposure
assessment methods have evolved from self-reported measures (e.g. proximity) (Janssen et al.
2003) to atmospheric dispersion (Oftedal et al. 2007) and land use regression (LUR) models
capturing within-city air pollution variations (Brauer et al. 2007; Gehring et al. 2010). Most LUR
models consider annual average concentrations which may over or under-estimate personal
exposures as traffic markers such as NO
are highly variable in time and space (Mölter et al.
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2010). Recently the temporal specificity of LUR models has been improved by applying forward
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