New Problems for an Old Design: Time-Series Analyses of Air Pollution and Health Jonathan M. Samet 1 , Francesca Dominici 2 , Aidan McDermott 2 , and Scott L. Zeger 2 September 18, 2002 1 The Johns Hopkins Bloomberg School of Public Health Department of Epidemiology, Rm W6041 615 N. Wolfe Street Baltimore, Maryland 21205 Phone: (410) 955-3286 Fax: (410) 955-0863 E-mail: jsamet@jhsph.edu 2 The Johns Hopkins Bloomberg School of Public Health Department of Biostatistics 615 N. Wolfe Street Baltimore, Maryland 21205