1 Theodore J. Witek Jr is with the Institute of Health Policy Management and Evaluation, Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario. James A. Scott is with the Division of Occupational and Environmental Health, Dalla Lana School of Public Health, and the Department of Laboratory Medicine and Pathobiology, Temerty Faculty of Medicine, University of Toronto. John R. Balmes is with the School of Medicine, University of California, San Francisco, and the School of Public Health, University of California, Berkeley.