Investigators: Paul Demers, Mieke Koehoorn, Mike Brauer, Cornel Lencar, Lillian Tamburic, Nina Clark from the University of British Columbia, and Catherine Karr from the University of Washington

Background
There is increasing recognition of the importance of early environmental exposures in childhood asthma development. Outdoor air pollution is a recognized asthma trigger, but it is unclear whether exposure influences incident disease. We investigated the effect of in utero and first year of life exposure to ambient air pollution on risk of asthma diagnosis in a population based birth-cohort.

Methods
All children born in Southwestern British Columbia in 1999 and 2000 (N=37,401) were assessed for incidence of asthma diagnosis at age 3 - 4 years using hospitalization and outpatient records. Individuals exposure to ambient air pollution was estimated for the gestational period and first year of life using high-resolution pollution surfaces derived from government monitoring station data as well as land use regression models adjusted for temporal variation. Logistic regression analyses were used to estimate effects of CO, NO, NO2, PM10, PM2.5, O3, SO2, black carbon, wood smoke and proximity to roads and point sources on asthma diagnosis.

Results
Follow-up data was available through 2003. 3,482 children (9%) were classified as asthma cases. Statistically significant increased risk of asthma diagnosis was observed with increased early life exposure to CO, NO, NO2, PM10, SO2, black carbon and proximity to point sources. Effects were generally larger for first year exposures than in utero exposures, and larger for girls than boys.
 
Interpretation
In a population-based birth cohort, we observed an increase in risk of asthma diagnosis for children exposed to higher levels of air pollution in early life.

Presentations and Posters
Presentations are in PDF format. The free Acrobat Reader is needed to access these documents.

Nina Clark at the Lung Health Research and Policy Day, March 2008.

2008
Effect of Early Life Exposure to Ambient Air Polution on Development of Childhood Asthma, presented by Nina Clark at the BC Lung Association's 5th Annual Air Quality and Health Workshop March 28, 2008 at the Sheraton Vancouver Wall Centre. Download presentation

2007
Effect of ambient air pollution exposure on development of childhood asthma, presented by Nina Clark at the ISEE 2007 Conference in Mexico City, September 5-9, 2007. Download poster or download abstract

Respiratory Health in Young Children and Air Pollution, presented by Nina Clark at the BAQS Meeting in Semiahmoo, January 2007. Downolad presentation (pdf)

Maps
These maps show annual average air pollution levels, asthma rates, and neighbourhood income levels in the Metro Vancouver area and Victoria.

For each forward sortation area (a geographical region where all postal codes start with the same three characters), you can see:

• the distribution of neighbourhood income
• the percentage of children who were diagnosed with asthma at age 4 or earlier
• the concentration of nitrogen oxide (NO), an important air pollutant

Click on each image to enlarge

Related articles:

Brauer M, Gehring U, Brunekreef B, de Jongste J, Gerritsen J, Rovers M, Wichmann HE, Wijga A, Heinrich J. Traffic-related air pollution and otitis media. Environ Health Perspect. 2006 Sep;114(9):1414-8.

Heinrich J, Raghuyamshi VS. Air pollution and otitis media: a review of evidence from epidemiologic studies. Curr Allergy Asthma Rep. 2004 Jul;4(4):302-9.