1. Department of Environmental Health, Harvard School of Public Health, Boston, MA
2. Gage Occupational and Environmental Health Unit, St. Michael's Hospital, Toronto, Ontario, Canada
3. Division of Occupational and Environmental Health, Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada
4. Division of Cardiovascular Medicine, University of Michigan, Ann Arbor, MI
5. Department of Occupational and Environmental Health, Universita' degli Studi di Milano and Fondazione Ca' Granda Policlinico, Milan, Italy
6. Department of Biostatistics, Harvard School of Public Health, Boston, MA
7. Channing Laboratory, Brigham and Women's Hospital, Harvard Medical School, Boston, MA