Abstract

Background

Nitrogen dioxide (NO2) is a marker for traffic-related air pollution, which exhibits strong spatial gradients in large cities. Previous studies have shown that in Canadian cities, exposure to ambient NO2 is greater in neighbourhoods of low socioeconomic status (SES). As a result of these differences in exposure, air pollution-related health problems may be more prevalent among children in lower SES urban neighbourhoods.

Data and Methods

Children younger than age 18 enumerated in the 2006 Census who lived in Toronto, Montreal or Vancouver were linked to published air pollution exposure land use regression models to assign exposure at the Dissemination Area (DA) level. Associations between both socioeconomic and visible minority status and exposure to ambient NO2 among children in these three cities were examined in a series of regression models (OLS and simultaneous autoregressive models that account for spatial autocorrelation).

Results

Children in lower income DAs in all three cities were exposed to higher NO2 concentrations than were children in higher income DAs (mean difference of 2 ppb between lowest and highest income quintiles). In some cities, DAs with larger percentages of children in lone-parent families and visible minority children were characterized by greater NO2 exposure.

Interpretation

The relatively high incidence of air pollution-related diseases (for example, asthma) among children in lower SES neighbourhoods may be attributable, at least in part, to variations in NO2 air pollution exposure within the same city.

Keywords

Air pollution, asthma, environmental health, income quintile, nitrogen dioxide

Findings

Environmental exposure to nitrogen dioxide (NO2), which is largely a by-product of vehicular exhaust and incomplete combustion of fossil fuels, has been associated with emergency hospitalizations for respiratory conditions among adults in lower income quartiles in large Canadian cities. Researchers have hypothesized that children may be even more vulnerable to the effects of air pollution because of their greater susceptibility to respiratory damage and faster respiratory rate, both of which exacerbate the effects of exposure. A time-series study of school-aged children in Vancouver observed that boys had a greater risk of asthma hospitalization after increases in ambient NO2 exposure if they were of low rather than high socioeconomic status (SES). [Full Text]

Authors

Lauren Pinault (lauren.pinault@canada.ca) and Michael Tjepkema are with the Health Analysis Division at Statistics Canada. Daniel Crouse is with the Department of Sociology, University of New Brunswick. Michael Jerrett is with the Fielding School of Public Health, University of California. Michael Brauer is with the School of Population and Public Health, University of British Columbia.

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What is already known on this subject?

  • In large Canadian cities, pollution-related health conditions such as asthma tend to be more common among adults and children of lower socioeconomic status (SES) than among those of higher SES.
  • In such cities, exposure to ambient air pollution is generally higher among adults of lower SES.
  • These differences in exposure to ambient air pollution may account for some of the observed differences in health conditions between these groups.

What does this study add?

  • Children in lower income Dissemination Areas (DAs) in the three largest Canadian cities are exposed to higher mean annual concentrations of nitrogen dioxide (NO2) than are children in higher income DAs—a difference of 1.5 to 1.9 ppb.
  • In Toronto and Vancouver, DAs with relatively high percentages of lone-parent families had greater exposure to ambient NO2.
  • In Montreal and Vancouver, DAs with relatively high percentages of visible minority children had greater exposure to ambient NO2.

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