From the Departments of Environmental Health and Epidemiology, Harvard School of Public Health, Boston, MA.
Editors’ note: This series addresses topics of interest to epidemiologists across a range of specialties. Commentaries start as invited talks at symposia organized by the Editors. This paper was presented at the Third North American Congress of Epidemiology held in Montreal in June 2011.
Editors’ note: Related articles appear on pages 785, 790, and 795.
The author reports no conflict of interest.
Correspondence: Marc G. Weisskopf, Department of Environmental Health/EOME, Harvard School of Public Health, Landmark Center, 401 Park Dr. PO Box 15697, Boston, MA 02215. E-mail: firstname.lastname@example.org.