1. Center for Environmental Medicine, Asthma and Lung Biology, and
2. Department of Medicine, University of North Carolina, Chapel Hill, North Carolina, USA
3. Department of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
4. Department of Medicine, University of California, Los Angeles, California, USA
5. Environmental Health Service, Rancho Los Amigos National Rehabilitation Center, Downey, California, USA
6. GlaxoSmithKline, King of Prussia, Pennsylvania, USA