Table 1.

Exposure Group Basis of Job/Task and Vessel or Vessel Type

Vessel and vessel type, description	Types of jobs/tasks	Estimation strategy: >5 measurements and <80% censoring. If absent:
Drilling rig vessels 4 vessels relatively stationary in the wellhead area (hot zone) and present from late April-early May to as late as December, 2010. There were approximately 100–200 people on a rig at any time.
Enterprise: led the efforts to stop the oil release, capturing and separating the oil from the entrained gas and flaring the gas	41 job groups across the rigs: • 38 specific jobs (examples found under each job group below) • Crew: operated the rig and helped directly with the response, e.g., roustabout, crane operator, derrickhand • Operations: people were often on the rig temporarily, performing technical tasks related to stopping the oil, e.g., ROV technician, methanol operations, mudlogger • “All jobs”: identified participants who received the first version of the questionnaire and so were not asked to provide a job title.	• Similar Job Title (e.g., ROV technician/supervisor) • Job Group (e.g., crew, operations). Crew, for example, comprised crane operators, seamen, roustabouts, and others. Operations included jobs such as mudloggers and ROV technicians. • Location of the job (inside vs. outside the vessel’s living areas and offices). Where these rules were insufficient: • The same job/vessel in a similar time period (time periods 1a and 1b were considered similar, as were time periods 2–4. Vessels had left the area by time period 5). • The same job on a sister ship in the same time period. The Enterprise and Q4000 were considered sister ships (both were involved in plugging the leaking well and flaring), as were the DD2 and DD3 (both drilled the relief wells).
Q4000: supported the Enterprise by pumping materials into the damaged well and flaring of the oil/gas, having no ability to separate the two
Development Driller II (DD2) : drilled a relief well
Development Driller III (DD3): drilled a relief well
Vessels with remotely operated vehicles (ROV) Most of these ROV vessels were fairly stationary. The ROV vessels arrived between April and June and had left the area by mid-September, 2010.
14 ROV vessels including the 2 ROVs vessels below: inspected and performed equipment repair work, assisted in the installation and removal of equipment, and provided the video to monitor the repair/positioning of work and the oil release on the Gulf floor 5000 ft below the water surface	• All outside workers on each vessel • All outside workers on all vessels	All participants on these vessels were assigned the job title “outside worker” because few workers likely worked only indoors. Where measurements were insufficient: • Pooled all “outside worker” measurements across all of the vessels of the same type and time period to form “all ROV” or “all research” vessel estimates. Where these rules were insufficient: • Grouped time periods (1a and 1b, vs. 2, 3, and 4 (the vessels had generally left the area by time period 5).
Skandi Neptune: injected dispersant near the Gulf floor at the point of the oil release		See above
REM Forza: sprayed dispersant as needed onto the water surface in the hot zone and source area in response to high (>70 ppm) volatile organic chemicals (VOC) levels as measured on ships with direct reading instruments.		See above
Research vessels Operated primarily under the auspices of the National Oceanic and Aeronautics Administration, Most research vessels went on multiple cruises, which typically lasted 1–3 weeks in duration and primarily covered the hot zone, source and offshore areas. The first cruise generally occurred in May or June and the last cruise generally was completed by August or September 2010
27 research vessels: collected data on various water characteristics, monitoried the oil plume, took water samples for later analysis, and monitored wildlife	• All outside workers on each vessel • All outside workers on all vessels	See ROV vessels above
Other vessels Included barges; marine, fishing, charter vessels; commercial boats, such as tug and crew boats; and smaller air and recreational boats located throughout the Gulf and along the shoreline. Generally worked from late April through the end of December, 2010.
Thousands of other vessels; 28 tasks1: supported the rig vessels’ operations; transported workers, chemicals and equipment to and from the vessels offshore; scouted for oil, laid boom to enclose the oil, maintained and removed it; skimmed or burned the oil; decontaminated vessels offshore to prevent oil on the hulls from contaminating waters as the vessel moved to shore; patrolled the beach and marsh areas.	• Various tasks, e.g., transport, scouting for oil, deploying boom, handling oily boom, skimming, burning	• A similar time period (i.e. 1a and 1b; 2 to 4; 5 and 6) from the same state Where the criteria still were not met: • Alabama and Florida were considered sister states (as were Louisiana and Mississippi,), using one state as a proxy for the other. If an estimate was not available from the sister state: • an estimate was calculated across measurements from all states.
Land Includes all tasks performed on land. Generally worked between late April, 2010 to June 2011
26 tasks1: scouted for oil on the beaches, cleaned these areas; put out boom and retrieved it along the shore; collected and cleaned wildlife; decontaminated vessels, equipment and personnel; and supported all of the aforementioned operations (supplying food and water, storage and positioning of equipment, security, administration, etc.).	• Various tasks, e.g., patrolling beaches, cleaning beaches, decontaminating vessels, decontaminating boom, kitchen workers, office workers	See other vessel tasks above

¹14 other activities were performed both on water and on land, including deconning workers; entering tanks, handled booms in shallow water, handling wildlife, hazardous waste handling, IH/safety, cleaning jetties