title: A national study of the association between traffic-related air pollution and adverse pregnancy outcomes in Canada, 1999-2008.
abstract: Numerous studies have examined the association of air pollution with preterm birth and birth weight outcomes. Traffic-related air pollution has also increasingly been identified as an important contributor to adverse health effects of air pollution. We employed a national nitrogen dioxide (NO2) exposure model to examine the association between NO2 and pregnancy outcomes in Canada between 1999 and 2008. National models for NO2 (and particulate matter of median aerodynamic diameter <2.5µm (PM2.5) as a covariate) were developed using ground-based monitoring data, estimates from remote-sensing, land use variables and, for NO2, deterministic gradients relative to road traffic sources. Generalized estimating equations were used to examine associations with preterm birth, term low birth weight (LBW), small for gestational age (SGA) and term birth weight, adjusting for covariates including infant sex, gestational age, maternal age and marital status, parity, urban/rural place of residence, maternal place of birth, season, year of birth and neighbourhood socioeconomic status and per cent visible minority. Associations were reduced considerably after adjustment for individual covariates and neighbourhood per cent visible minority, but remained significant for SGA (odds ratio 1.04, 95%CI 1.02-1.06 per 20ppb NO2) and term birth weight (16.2g reduction, 95% CI 13.6-18.8g per 20ppb NO2). Associations with NO2 were of greater magnitude in a sensitivity analysis using monthly monitoring data, and among births to mothers born in Canada, and in neighbourhoods with higher incomes and a lower proportion of visible minorities. In two pollutant models, associations with NO2 were less sensitive to adjustment for PM2.5 than vice versa, and there was consistent evidence of a dose-response relationship for NO2 but not PM2.5. In this study of approximately 2.5 million Canadian births between 1999 and 2008, we found significant associations of NO2 with SGA and term birth weight which remained significant after adjustment for PM2.5, suggesting that traffic may be a particularly important source with respect to the role of air pollution as a risk factor for adverse pregnancy outcomes.
authors.affiliation: Population Studies Division, Health Canada, 420-757 West Hastings St. - Federal Tower, Vancouver, British Columbia, Canada V6C 1A1. Electronic address: dave.stieb@hc-sc.gc.ca.
authors.forename: David M
authors.initials: DM
authors.lastname: Stieb
authors.affiliation: Population Studies Division, Health Canada, AL 1907A, Tunney's Pasture, Ottawa, Ontario, Canada K1A 0K9. Electronic address: li.chen@hc-sc.gc.ca.
authors.forename: Li
authors.initials: L
authors.lastname: Chen
authors.affiliation: College of Public Health and Human Sciences, Oregon State University, Milam Hall 20C, Corvallis, OR 97331, USA. Electronic address: perry.hystad@oregonstate.edu.
authors.forename: Perry
authors.initials: P
authors.lastname: Hystad
authors.affiliation: Geographic Information Health and Exposure Science Laboratory (GIS HEAL), School of Public Health, University of California, Berkeley, Berkeley, CA 94720-7360, USA. Electronic address: beckerman@berkeley.edu.
authors.forename: Bernardo S
authors.initials: BS
authors.lastname: Beckerman
authors.affiliation: Department of Environmental Health Sciences, Fielding School of Public Health, University of California Los Angeles, 650 Charles E. Young Drive South, 56-070B CHS, Los Angeles, CA 90095, USA. Electronic address: mjerrett@ucla.edu.
authors.forename: Michael
authors.initials: M
authors.lastname: Jerrett
authors.affiliation: Health Analysis Division, Statistics Canada, 100 Tunney's Pasture Driveway, Ottawa, Ontario, Canada K1A OT6. Electronic address: michael.tjepkema@canada.ca.
authors.forename: Michael
authors.initials: M
authors.lastname: Tjepkema
authors.affiliation: Department of Sociology, University of New Brunswick, Tilley Hall, Room 20, 9 Macaulay Lane, P.O. Box 4400, Fredericton, New Brunswick, Canada E3B 5A3. Electronic address: dan.crouse@unb.ca.
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Crouse
authors.affiliation: Special Surveys Division, Statistics Canada, 100 Tunney's Pasture Driveway, Ottawa, Ontario, Canada K1A OT6. Electronic address: walter.omariba@canada.ca.
authors.forename: D Walter
authors.initials: DW
authors.lastname: Omariba
authors.affiliation: Department of Sociology, University of New Brunswick, Tilley Hall, Room 20, 9 Macaulay Lane, P.O. Box 4400, Fredericton, New Brunswick, Canada E3B 5A3. Electronic address: paul.peters@unb.ca.
authors.forename: Paul A
authors.initials: PA
authors.lastname: Peters
authors.affiliation: Department of Physics and Atmospheric Science, Dalhousie University, 6310 Coburg Road PO Box 15000, Halifax, NS, Canada B3H 4R2. Electronic address: kelaar@dal.ca.
authors.forename: Aaron
authors.initials: A
authors.lastname: van Donkelaar
authors.affiliation: Department of Physics and Atmospheric Science, Dalhousie University, 6310 Coburg Road PO Box 15000, Halifax, NS, Canada B3H 4R2; Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA. Electronic address: randall.martin@dal.ca.
authors.forename: Randall V
authors.initials: RV
authors.lastname: Martin
authors.affiliation: Population Studies Division, Health Canada, AL 1907A, Tunney's Pasture, Ottawa, Ontario, Canada K1A 0K9. Electronic address: rick.burnett@hc-sc.gc.ca.
authors.forename: Richard T
authors.initials: RT
authors.lastname: Burnett
authors.affiliation: Maternal, Child and Youth Health, Surveillance and Epidemiology Division, Public Health Agency of Canada, 4th floor, 785 Carling Ave. AL 6804A, Ottawa, Ontario, Canada K1A 0K9. Electronic address: shiliang.liu@phac-aspc.gc.ca.
authors.forename: Shiliang
authors.initials: S
authors.lastname: Liu
authors.affiliation: Population Studies Division, Health Canada, AL 1907A, Tunney's Pasture, Ottawa, Ontario, Canada K1A 0K9. Electronic address: marc.h.smith-doiron@hc-sc.gc.ca.
authors.forename: Marc
authors.initials: M
authors.lastname: Smith-Doiron
authors.affiliation: Air Health Science Division, Health Canada, Ottawa, Ontario, Canada. Electronic address: rose.dugandzic@hc-sc.gc.ca.
authors.forename: Rose M
authors.initials: RM
authors.lastname: Dugandzic
mesh_terms: D000293:Adolescent; D000328:Adult; D000393:Air Pollutants / Q000032:analysis*; D002170:Canada / Q000453:epidemiology; D005260:Female; D006801:Humans; D007230:Infant, Low Birth Weight; D008297:Male; D018986:Motor Vehicles; D009585:Nitrogen Dioxide / Q000032:analysis*; D011247:Pregnancy; D011256:Pregnancy Outcome / Q000453:epidemiology*; D047928:Premature Birth / Q000453:epidemiology*; D001335:Vehicle Emissions; D055815:Young Adult
chemical_list: D000393:Air Pollutants; D001335:Vehicle Emissions; D009585:Nitrogen Dioxide
keywords: Air pollution; Birth weight; Nitrogen dioxide; Preterm birth; Traffic