1. Harvard School of Public Health, Boston, Massachusetts, USA
2. Channing Laboratory, Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston, Massachusetts, USA
3. Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
4. Division of Respiratory Disease Studies, National Institute for Occupational Safety and Health, Morgantown, West Virginia, USA
5. University of Massachusetts Lowell, Lowell, Massachusetts, USA