1. Department of Urban and Environmental Policy and Planning, Tufts University, Medford, Massachusetts, USA
2. Exposure, Epidemiology and Risk Program, Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts, USA
3. Channing Laboratory, Brigham and Women’s Hospital and Harvard Medical School, Boston, Massachusetts, USA
4. Department of Epidemiology, Harvard School of Public Health, Boston, Massachusetts, USA
5. Pulmonary and Critical Care Medicine Section, Medical Service, VA Boston Healthcare System, West Roxbury, Massachusetts, USA