1. College of Medicine, University of Ibadan, Ibadan, Nigeria
2. Institute of Public Health, Georgia State University, Atlanta, GA 30302-3995, USA
3. Department of Environmental and Occupational Health, School of Public Health, University of Medicine and Dentistry of New Jersey (UMDNJ), Piscataway, NJ 08854, USA
4. Environmental and Occupational Health Sciences Institute, UMDNJ-Robert Wood Johnson Medical School, Rutgers University, Piscataway, NJ 08854, USA