Assessing Exposures from the Deepwater Horizon Oil Spill Response and Clean-up

Abstract

The GuLF Study is investigating adverse health effects from work on the response and clean-up after the Deepwater Horizon explosion and oil release. An essential and necessary component of that study was the exposure assessment. Bayesian statistical methods and over 135 000 measurements of total hydrocarbons (THC), benzene, ethylbenzene, toluene, xylene, and n-hexane (BTEX-H) were used to estimate inhalation exposures to these chemicals for >3400 exposure groups (EGs) formed from three exposure determinants: job/activity/task, location, and time period. Recognized deterministic models were used to estimate airborne exposures to particulate matter sized 2.5 µm or less (PM2.5) and dispersant aerosols and vapors. Dermal exposures were estimated for these same oil-related substances using a model modified especially for this study from a previously published model. Exposures to oil mist were assessed using professional judgment. Estimated daily THC arithmetic means (AMs) were in the low ppm range (<25 ppm), whereas BTEX-H exposures estimates were generally <1000 ppb. Potential 1-h PM2.5 air concentrations experienced by some workers may have been as high as 550 µg m-3. Dispersant aerosol air concentrations were very low (maximum predicted 1-h concentrations were generally <50 µg m-3), but vapor concentrations may have exceeded occupational exposure excursion guidelines for 2-butoxyethanol under certain circumstances. The daily AMs of dermal exposure estimates showed large contrasts among the study participants. The estimates are being used to evaluate exposure-response relationships in the GuLF Study.

Keywords: Deepwater Horizon; PM2.5; dispersant; exposure assessment; total hydrocarbons.

Figure 1.

Inhalation exposure estimates for total hydrocarbons (THC), benzene, ethylbenzene, toluene, xylene and n-hexane (BTEX-H) by time period (THC = ppm; BTEX-H = ppb) for ‘All rig vessels’, ‘All ROVs’, ‘All fire control vessels’, ‘All research vessels’, ‘All Other Water Operations’, and ‘All Land Operations’. ROV vessels: vessels that piloted remotely operated vehicles (ROVs). The benzene graph showing the higher AMs for ‘All Other Water Operations’ is due to an artifact of the methods used by the labs to calculate the limits of detection.

Figure 2.

Dermal exposure estimates for total hydrocarbons, benzene, ethylbenzene, toluene, xylene and n-hexane from oil by time period (Gulf Dream Units, GDUs) for ‘All Rigs’, ‘All ROVs’, ‘All Research Vessels’, ‘All Water Operations’, and ‘All Land Operations’. ROV vessels: vessels that piloted remotely operated vehicles (ROVs). These vessels left the area after TP3, so no estimates were developed. Burner fire control vessels were present only in TP1b and had no dermal exposures to any oil-related substance.