1. Department of Environmental and Occupational Health Sciences, School of Public Health, University of Washington, Seattle, WA, USA
2. Department of Community and Environmental Health, School of Allied Health Sciences, College of Health Sciences, Boise State University, Boise, ID, USA
3. Department of Biostatistics, School of Public Health, University of Washington, Seattle, WA, USA
4. Safety, Health, and Industrial Hygiene Department, School of Mines and Engineering, Montana Tech, Butte, MT, USA