1. Department of Geography, McMaster University, Hamilton, Ontario L8S 4K1, Canada,
2. Department of Community Health, Waterloo Region, Waterloo, Ontario N2J 4V3, Canada,
3. Department of Epidemiology, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada,
4. Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Ontario L8N 3Z5, Canada