1. Exposure, Epidemiology and Risk Program, Department of Environmental Health, Harvard School of Public Health, Boston, MA, USA
2. Channing Laboratory, Brigham and Women’s Hospital and Harvard Medical School, Boston, Massachusetts, USA
3. Department of Epidemiology, and
4. Department of Biostatistics, Harvard School of Public Health, Boston, Massachusetts, USA
5. Pulmonary and Critical Care Medicine Section, VA Boston Healthcare System, Boston, Massachusetts, USA
6. School of Public Health, University of California, Berkeley, California, USA