Modeling the intraurban variability of ambient traffic pollution in Toronto, Canada.

The objective of this paper is to model determinants of intraurban variation in ambient concentrations of nitrogen dioxide (NO2) in Toronto, Canada, with a land use regression (LUR) model. Although researchers have conducted similar studies in Europe, this work represents the first attempt in a North American setting to characterize variation in traffic pollution through the LUR method. NO2 samples were collected over 2 wk using duplicate two-sided Ogawa passive diffusion samplers at 95 locations across Toronto. Independent variables employed in subsequent regression models as predictors of NO2 were derived by the Arc 8 geographic information system (GIS). Some 85 indicators of land use, traffic, population density, and physical geography were tested. The final regression model yielded a coefficient of determination (R2) of .69. For the traffic variables, density of 24-h traffic counts and road measures display positive associations. For the land use variables, industrial land use and counts of dwellings within 2000 m of the monitoring location were positively associated with NO2. Locations up to 1500 m downwind of major expressways had elevated NO2 levels. The results suggest that a good predictive surface can be derived for North American cities with the LUR method. The predictive maps from the LUR appear to capture small-area variation in NO2 concentrations. These small-area variations in traffic pollution are probably important to the exposure experience of the population and may detect health effects that would have gone unnoticed with other exposure estimates.

Do socioeconomic characteristics modify the short term association between air pollution and mortality? Evidence from a zonal time series in Hamilton, Canada.

STUDY OBJECTIVE: To assess the short term association between air pollution and mortality in different zones of an industrial city. An intra-urban study design is used to test the hypothesis that socioeconomic characteristics modify the acute health effects of ambient air pollution exposure. DESIGN: The City of Hamilton, Canada, was divided into five zones based on proximity to fixed site air pollution monitors. Within each zone, daily counts of non-trauma mortality and air pollution estimates were combined. Generalised linear models (GLMs) were used to test mortality associations with sulphur dioxide (SO(2)) and with particulate air pollution measured by the coefficient of haze (CoH). MAIN RESULTS: Increased mortality was associated with air pollution exposure in a citywide model and in intra-urban zones with lower socioeconomic characteristics. Low educational attainment and high manufacturing employment in the zones significantly and positively modified the acute mortality effects of air pollution exposure. DISCUSSION: Three possible explanations are proposed for the observed effect modification by education and manufacturing: (1) those in manufacturing receive higher workplace exposures that combine with ambient exposures to produce larger health effects; (2) persons with lower education are less mobile and experience less exposure measurement error, which reduces bias toward the null; or (3) manufacturing and education proxy for many social variables representing material deprivation, and poor material conditions increase susceptibility to health risks from air pollution.

The pattern of counterurbanization in the Federal Republic of Germany, 1977-85.

County-level data are used to examine the evidence for turnaround migration from urban to rural areas in the Federal Republic of Germany during the period 1978-1985. "The coexistence of suburbanization and counterurbanization for the 1978-85 time period is demonstrated. Young adults, 18-25 years of age, gravitated towards the urban cores of metropolitan areas and smaller urban areas. All the other age-groups moved mainly towards the outer suburbs of metropolitan areas, the suburbs of second-tier cities, and the rural counties. The two migration matrices indicate that counterurbanization at the level of regional planning areas was not present in 1977 but started in 1978 and it was present in 1983. At the same spatial level, evidence of a net gain of metropolitan areas from second-tier cities and rural areas is also provided for 1977. This pattern was reversed for the 1978-85 period."

An analysis of migratory systems: 1. Theory.

This is the first of a planned series of three papers in which the authors attempt to combine evolutionary migration models with stochastic utility theory. This first paper deals with the evolution of migratory systems. Such systems are first defined, and the foundations upon which their evolution is based are described. The paper concludes with a discussion of disequilibrium, which is central to the series. "Disequilibrium is related to the concept of a steady state, the existence of which is established for nonlinear migratory systems of the type discussed here."

An analysis of migratory systems: 2. Operational framework.

"This is the second in a series of three interrelated papers which aim to combine evolutionary migration models with stochastic utility theory. The first paper dealt with migratory dynamics. Here the details are given of a choice model, established by McFadden, which can be used in conjunction with migratory dynamics thus providing an explicit link between the macroproperties of the population system and human behaviour. First, the structure of transition probabilities is derived under a two-level decision to migrate. An argument is then given about the empirical form of these probabilities, and the discussion closes with a method which can be used for their maximum likelihood estimation."

An exploratory spatial analysis of pneumonia and influenza hospitalizations in Ontario by age and gender.

Pneumonia and influenza represent a significant public health burden in Canada and abroad. Knowledge of how this burden varies geographically provides clues to understanding the determinants of these illnesses, and insight into the effective management of health-care resources. We conducted a retrospective, population-based, ecological-level study to assess age- and gender-specific spatial patterns of pneumonia and influenza hospitalizations in the province of Ontario, Canada from 1992 to 2001. Results revealed marked variability in hospitalization rates by age, as well as clear and statistically significant patterns of high rates in northern rural counties and low rates in southern urban counties. A moderate yet significant level of positive spatial autocorrelation (Moran's I=0.21, P<0.05) was found in the global data, with significant, age-specific clusters of high values or 'hot spots' identified in several northern counties. Findings illustrate the need for geographically focused prevention strategies, and resource and service allocation policies informed by regional and population-specific demands.

A framework for the analysis of psychiatric health facility utilization.

Existing research that examines the general problem of health facility use often lacks sound theoretical specification. This problem is partly a function of conceptual difficulties in explaining health seeking behaviour and an absence of appropriate data with which to calibrate modelling endeavours. These problems are addressed in this paper where a logit model of health seeking behaviour and health facility use derived from discrete choice theory is presented. The structure of the model is general but in this case it is developed in the context of mental health facility use. A data set from Auckland, New Zealand is utilized to apply the modelling ideas presented. Results show that discrete choice theory can be adapted to the problem of mental health facility usage under conditions where the health care system offers real choice at any given level of care. In this case real choice implies a well-developed array of alternative facilities to choose from.

Incorporating the effects of spatial structure in discrete choice models of migration.

Discrete-choice theory and logit models are evaluated for their usefulness in analyzing migration patterns in a zonal system. The authors "argue that spatial effects and more specifically the relative location of zones are not taken into account in such analyses. We, therefore, introduce a measure of spatial structure and advocate its usage as a predictor of migration in such models. In an example of intrametropolitan migration in Toronto [Canada], we demonstrate that this variable is not only significant but also it improves the performance of all the other variables with the greatest impact on the distance between zones. In addition, inclusion of this variable improves the overall performance of the model in terms of residuals."