1. a Occupational Health Program, Department of Environmental Health, Rm 1402, HSPH-1 Harvard School of Public Health 655 Huntington Avenue Boston MA 02115 USA
2. d Institute of Occupational Safety and Health, Council of Labor Affairs Taipei Taiwan
3. c Liberty Mutual Research Institute for Safety Hopkinton MA USA
4. e Institute of Environmental Health Science, National Yang-Ming University Taipei Taiwan
5. b Department of Biostatistics Harvard School of Public Health Boston MA USA