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Geographies of susceptibility and exposure in the city: environmental inequity of traffic-related air pollution in Toronto/Les geographies de susceptibilite et d'exposition dans la ville : l'injustice de l'environnement de pollution de l'air concernant la circulation a Toronto.

Article Excerpt
Abstracts

This paper analyses the association between traffic-generated air pollution and neighbourhood socioeconomic status in Toronto. Based on a special sampling campaign of 95 nitrogen dioxide monitors in 2002, ambient concentrations are estimated and validated at the micro-geographic scale within neighbourhoods. Exposures are modelled for their association with neighbourhood socio-economic markers drawn from the 2001 Canadian Census producing some expected positive associations with air pollution (low incomes and low education) and other surprising associations (dwelling values and high-status occupations). The results join a growing body of environmental justice studies that point to subtle and sometimes contrarian evidence. New methodologies, hazards and ongoing socio-spatial processes may be generating ever more complex environmental (in)equity relationships.

Resumes

>. Cet article analyse l'association entre la pollution de l'air produite par la circulation et le statut socio-economique des quartiers a Toronto. Les emissions de la circulation sont maintenant la source la plus grande de la pollution de l'air dans la ville Nord-americaine typique bien que leur diversite spatiale ne soit pas toujours appreciea. Peut-etre plus que toute autre ville au Canada, les emissions de la circulation a Toronto refletent beaucoup plus une distribution spatiale heterogene parce que la Ville possede un reseau etendu de routes importantes, des routes nationales et des autoroutes. Si les emissions de la circulation de Toronto sont spatialement heterogenes, c'est de meme pour sa geographie sociale. La region meme exemplifie, et dans quelques cas represente, des exemples extremes des disparites sociales et de la segregation spatiale des grandes metropoles canadiennes. Comment se croisent les emissions de transport et cette geographie sociale complexe pour produire des geographies de susceptibilite et d'exposition?

Base sur une campagne d'echantillonnage speciale de 95 moniteurs de dioxyde d'azote en 2002, les concentrations ambiantes sont estimees et validees a l'echelle du quartier. Les expositions sont modelees pour leur association avec les indicateurs socio-economiques de quartier tires du Recensement Canadien 2001 en incluant des valeurs d'habitation, de revenu du menage, de statut de famille, de statut de minorite immigre/visible et des indicateurs du metier. Un systeme informatique geographique (ArcGIS 9.1 ESRI, Redlands, CA) est utilise pour incorporer le quartier socio-economique et les valeurs de pollution de l'air dans l'analyse. L'hypothese principale est que les quartiers en bas de l'echelle SES portent le plus grand fardeau d'exposition chronique de NO2 produit par la circulation.

Les resultats des modeles produisent quelques associations positives attendues avec la pollution de l'air (les bas revenus et un niveau d'education bas) et d'autres associations surprenantes (les valeurs des habitations et des occupations de haut statut). Les resultats rejoignent un corps grandissant d'etudes de justice de l'environnement qui demontrent des resultats subtils et quelquefois contradictoire. Des nouvelles methodologies, des hasards et des processus socio-spatiaux en cours peuvent generer des rapports d'equite de l'environnement plus complexe. La recherche future peut raffiner cette analyse en poursuivant un certain nombre de pistes, incluant l'analyse d'une gamme de polluants et une analyse o une echelle spatiale alternative.

Introduction

The scope of environmental justice research has widened considerably in recent years to reflect not only inequities in environmental health exposures but also interest in health effects and a greater range of hazards. Underpinning these developments - and the focus of this paper- are prescriptions for and critiques of the methods used in environmental justice research and the substantive conclusions that follow (Brulle and Pellow 2006; Downey 2006; Mohai and Saha 2006; Bowen 2002). A principal concern is that high-quality environmental monitoring data are rarely available or publicly accessible. Using data from a large air pollution sampling campaign in Toronto, we analyze the geographies of susceptibility and exposure to traffic-related air pollution, namely nitrogen dioxide (N[O.sub.2]), within and across neighbourhoods.

Traffic emissions are now the single largest source of air pollution in the typical North American city (Molina and Molina 2004). Perhaps more than any other city in Canada, traffic emissions in Toronto reflect a much more heterogeneous spatial distribution because the City has an extensive network of major roads, highways and expressways. Recent studies from the nearby City of Hamilton have suggested that proximity to roadways may advance mortality rates by up to 2.5 years in the general population and is associated with an increase in cardiopulmonary death of over 20% (Finkelstein et al 2003).

If Toronto traffic emissions are spatially heterogeneous so too is its social geography. The region both represents the social disparities and spatial segregation of large Canadian metropolises. It has some of the most extreme cases of intra-urban wealth and despair gradients. However, contrary patterns also exists with some new immigrants stratified by status and type (e.g. refugees) veering away from traditional central-city settlement patterns via direct suburban settlement (Hiebert 2000). Using high-resolution pollution data, our question is whether and to what extent social geography and N[O.sub.2] systematically map onto one another in Toronto. We begin with an overview of each of these issues and then turn to the data and methods used to bring the urban physical and social environments together. We conclude with a discussion of the broad transportation and socioeconomic trends that improve understanding of environmental justice in the increasingly variegated landscape of the North American city.

Background: Methodological Concerns

Now into its third decade, environmental justice research grew out of early influential studies (e.g. US GAO 1982; Bullard 1990) that led to both distributional research on inequities of exposures to health hazards and process research on the socio-political mechanisms that generate such inequities (Cutter 1995). In the former camp the noted UCC (1987) Commission on Racial Justice found that in the United States people of colour were twice as likely as Whites to live in a community with a commercial hazardous waste facility and three times as likely to have multiple facilities. The political power of these civil rights statements meant that research strategies developed around revealing the presence and degree of disproportionate co-location of such facilities and poor and visible minority communities (e.g. Glickman 1994).

Much of the literature on methodology in the last decade revolves around the simple assumption that underlies co-location studies; in terms of the spatial extent of hazards; the modifiable areal units of administrative boundaries and related ecological fallacy; the toxicity and assignment of exposures; and the relationship to health outcomes. Researchers have redressed...

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