Ontario Public Health Units Research Articles

An Analysis of the Geographic Variation in Cancer Incidence and its Determinants in Ontario

Cancer incidence data for the Ontario Public Health Units in 1980-91 were examined to investigate regional patterns and the existence of outlier values after adjustment for known risk factors. Candidate risk factors were derived from the Ontario Health Survey and the census. Weighted regressions were fit to the data, and the spatial pattern of the residuals was analyzed. The number of outlier data points with significant elevations or reductions in risk was close to that expected by chance. They were dispersed geographically, and occurred in a variety of cancer types. We conclude that, in general, most of the geographic variation in cancer risk can be associated with variation in known risk factors, and that there appear to be no broad regional effects remaining after adjustment for these factors. A few cancer sites provide limited evidence of regional effects that may warrant further investigation.

Heart Health Promotion: Predisposition, Capacity and Implementation in Ontario Public Health Units, 1994–96

The Canadian Heart Health Initiative-Ontario Project (CHHIOP) investigates predisposition and capacity in Ontario public health departments to implement community-based heart health promotion activities. The research draws upon diffusion of innovations theory and recent work on ecological approaches to health promotion within which public health agencies are seen to play a central role. Mail-back surveys were completed by heart health staff in all 42 health departments in 1994 and 1996. Predisposition and capacity were measured as the importance and effectiveness ascribed to 18 organizational practices supportive of community heart health activities. Level of implementation was reported for 74 activities spanning a range of risk factors and settings. Predisposition, capacity and implementation scores increased between 1994 and 1996. The findings confirm positive correlations between predisposition and capacity and between capacity and implementation.

Assessment of a Bayesian multivariate interpolation approach for health impact studies

Health impact studies of air pollution often require estimates of pollutant concentrations at locations where monitoring data are not available, using the concentrations observed at other monitoring stations and possibly at different time periods. Recently, a Bayesian approach for such a temporal and spatial interpolation problem has been proposed by Le. Sun and Zidek (1997). One special feature of the method is that it does not require all sites to monitor the same set of pollutants. This feature is particularly relevant in environmental health studies where pollution data are often pooled together from several monitoring networks which may or may not monitor the same set of pollutants. The methodology is applied to the data in the Province of Ontario, where monthly average concentrations for summer months ofnitrogen dioxide (NO 2 in μg/m 3 ), ozone (O 3 in ppb), sulphur dioxide (SO in μg/m 3 ) and sulfate ion (SO 4 in μg/m 3 ) are available for the period from January I of 1983 to December 31 of 1988 at 31 ambient monitoring sites. Detailed descriptions of spatial interpolation for air pollutant concentrations at 37 approximate centroids of Public Health Units in Ontario using all available data are presented. The methodology is empirically assessed by a cross-validation study where each of the 31 sites is successively removed and the remaining sites are used to predict its concentration levels. The methodology seems to perform well.