1. Department of Family and Community Medicine, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA
2. National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
3. North Carolina Farmworkers Project, Benson, North Carolina, USA
4. Department of Biostatistical Sciences, Division of Public Health Sciences and
5. Department of Epidemiology and Prevention, Division of Public Health Sciences, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA