1. Division of Field Studies and Engineering, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, Cincinnati, Ohio, USA
2. Respiratory Health Division, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, Morgantown, WV, USA
3. Professional Services Partners, Contractors with Respiratory Health Division, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, Wallace, Oak Park, IL, USA