Analysis of Potential for Human Exposure to Aerial Dispersant Application

Abstract

ABSTRACT The response to the Macondo oil well blow-out in the Gulf of Mexico in 2010, utilized significant quantities of dispersants. The way dispersants make oil available to natural biodegradation, their environmental effects, and overall benefits in oil spill reponse were well understood by the oil and spill response industries. These materials have been studied and improved for over 40 years. In spill response scenarios like Macondo, the large quantities of dispersant utilized raised concerns regarding human exposures. This paper provides the following:An analysis of dispersant spray drift from aerial application of oil dispersant.A review of the exclusion zones established by the Region IV and VI Regional Response Teams (RRT’s).Evidence that the controls to protect cleanup workers were effective. The volume of chemical dispersant utilized in the Macondo response is often presented as an indicator suggesting human exposure. While the volume is interesting, the application, its dilution in the water column, and its environmental persistence are far better measures of the potential for human exposure. Furthermore, the controls that were required by the Federal–On-Scene-Coordinator to ensure responder and public safety are critical considerations. These controls were designed and implemented by Regulators and supported by appropriate health professionals to avoid the possibility of human exposure. These controls were established and published well before the Macondo spill. Studies were undertaken during the 2010 spill response to examine surface and subsurface waters to determine the presence of dispersant constituents. Spill response worker exposure was evaluated in both offshore and on-shore clean-up areas during dispersant application. The studies found no evidence that response workers were exposed to levels of constituents that approached occupational exposure limits.