The design of the Gulf STUDY is described in detail elsewhere (Kwok et al., in press ). In brief, persons who were involved in any aspect of DWH oil spill work and/or completed worker safety training in anticipation of performing spill-related work were identified from administrative records. Potential participants were recruited by telephone and invited to complete a 30–60 minute telephone enrollment interview. Participants were required to be at least 21 years of age at enrollment. Interviews were conducted in English, Spanish, or Vietnamese. Enrollment interviews were conducted from March 2011 to March 2013. Individuals who completed the telephone interview constitute the GuLF STUDY Cohort (N=32,608). All cohort members who lived in one of the Gulf States (Alabama, Florida, Louisiana, Mississippi, and east Texas) and spoke English or Spanish were invited to participate in a home visit. Home visits were conducted from May 2011 to May 2013. The Home Visit Subcohort is composed of the 11,193 cohort members who completed a home visit. Only 136 (1.2%) home visit participants were known to be still engaged in spill-related work at the time of their home visit, with a median of 21 months and maximum of 35 months since the end of spill-related work among all home visit participants. Finally, a stratified random sample of Home Visit Subcohort members residing in selected coastal and adjacent counties in Louisiana and Alabama and oversampled for oil spill workers constitute the Biomedical Surveillance Subcohort (N=4,050; 91% workers). This subcohort was established for characterization of blood parameters (in assays requiring fresh blood), for detailed urinalysis at the time of the home visit, and for possible invitation to periodic follow-up clinical examinations depending on proximity to subsequently established clinics in those two states.
Certified Medical Assistants (CMA), who have been trained in phlebotomy and other clinical procedures as part of their professional certification, served as field agents and underwent extensive additional training and certification by the GuLF STUDY research team prior to conducting the home visits. They were also subjected to regular quality control review and day-to-day oversight by the GuLF STUDY research team central field manager and a field manager located in each state.
During the home visit, field agents obtained informed consent, collected several physiologic and anthropometric measures, conducted a pulmonary function test, administered an additional questionnaire, and collected biological specimens and house dust samples. The three hour home visits were conducted 7 days per week, from early morning into the early evening. Whenever possible, home visits for members of the Biomedical Surveillance Subcohort were scheduled early on Monday through Thursday to facilitate overnight shipping of specimens. An average of 119 home visits per week was conducted.
Characteristics of the Home Visit Subcohort are shown inTable 1 .
Certified Medical Assistants (CMA), who have been trained in phlebotomy and other clinical procedures as part of their professional certification, served as field agents and underwent extensive additional training and certification by the GuLF STUDY research team prior to conducting the home visits. They were also subjected to regular quality control review and day-to-day oversight by the GuLF STUDY research team central field manager and a field manager located in each state.
During the home visit, field agents obtained informed consent, collected several physiologic and anthropometric measures, conducted a pulmonary function test, administered an additional questionnaire, and collected biological specimens and house dust samples. The three hour home visits were conducted 7 days per week, from early morning into the early evening. Whenever possible, home visits for members of the Biomedical Surveillance Subcohort were scheduled early on Monday through Thursday to facilitate overnight shipping of specimens. An average of 119 home visits per week was conducted.
Characteristics of the Home Visit Subcohort are shown in