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in symptoms such as nausea, dizziness, headaches, coughing, and fatigue. Oil spill response teams should monitor air qual- ity and use respirators to protect themselves from these fumes when appropriate. What is the Coast Guard doing about it? The Coast Guard Office of Commercial Vessel Compliance reviews and approves vessel response plans to ensure that the appropriate oil spill containment and cleanup resources are available to respond to worst-case discharges. Crude oil ship- ping is subject to multiple regulations; two relevant regulations include 46 CFR 30 – 39, which determine engineering, opera- tion, and safety requirements for barges carrying f ammable and combustible liquids, and specif c requirements in 46 CFR 30 – 39 are determined by f ashpoint and Reid Vapor Pressure of the actual cargo. Also, 33 CFR 155.1020 def nes different groups of oils with respect to their specif c gravity for the purpose of response plan requirements. About the authors: 1/c Nickolette Morin is a cadet at the United States Coast Guard Acad- emy, studying Marine and Environmental Science. She is interested in a career in response. CDR Gregory Hall is the associate dean of academics at the United States Coast Guard Academy, where he teaches Petroleum and Oil Spill Sci- ence. He serves as the editor for the Proceedings of the International Oil Spill Conference, and his area of scholarship includes studying the weathering dynamics of petroleum spills. Acknowledgements: The authors would like to thank Mr. Kurt Hansen (USCG Research & Development Center), CDR James Weaver (CG-MER-3), LT Sara Booth (CG-MER-3), and LT Andrew Murphy (CG-ENG-5) for their input and advice. References: Diluted Bitumen. Association of Oil Pipe Lines, 2013. Available at www.api.org/~/ media/Files/Oil-and-Natural-Gas/Oil_Sands/Diluted-Bitumen.pdf. Enbridge Incorporated Hazardous Liquid Pipeline Rupture and Release Mar- shall, Michigan. National Transportation Safety Board, 2010. Available at www.ntsb.gov/doclib/ reports/2012/PAR1201.pdf. Federal Government Technical Report: Properties, Composition, and Marine Spill Behav- iour, Fate and Transport of Two Diluted Bitumen Products from the Canadian Oil Sands. Environment Canada Emergencies Science and Technology, 2013, p.p. 1-85. Fingas, M. Review of Diluted Bitumen Properties Relevant to Spill Cleanup. Spill Sci- ence, 2014, p.p. 1-25. Shigenaka, G. et al. NOAA. Transporting Alberta Oil Sands Products: Def ning the Issues and Assessing the Risks. NOAA Technical Memorandum NOS OR&R 44, 2013, p.p. 5-153. Welch, L.C., Mullee, A., Shrestha, A., and Wade, D. Oil and Water: Tar Sands Crude Shipping Meets the Great Lakes? Alliance for the Great Lakes, 2013, p.p. 1-31. What is it? Diluted bitumen (Dilbit) is created when heavy sour oil (bitu- men) is extracted from oil sands and combined with a lighter hydrocarbon-based diluent to facilitate transportation. Two common diluents are natural gas condensate and synthetic crude. Dilbit consists of approximately 30 percent diluent to 70 percent bitumen, or in the case of synthetic crude oil, 50 per- cent diluent to 50 percent bitumen. These diluents are derived from crude oil themselves; therefore, there are no exotic com- pounds included in Dilbit that one would not expect to be pres- ent in more "traditional" crude oils. The commercial use of Dilbit is similar to that of all crude oil including transportation fuel such as jet fuel, gasoline, and die- sel, all of which require different ref ning processes to obtain. Why Should I Care? Environmental Concerns: In a spill of diluted bitumen, the diluents do not solely evapo- rate; therefore, the spill does not return to the properties of the starting bitumen (before dilution), but instead weathers to a heavier oil. Lighter fractions will evaporate or dissolve, leaving the more viscous compounds behind. The heavier oil may then sink once it acquires more sediment from a coastal or inland environment. Weathered diluted bitumen has properties between a weathered synthetic crude and bitumen. Some of the changes to the proper- ties include an increase in density and a lower f ashpoint for 1-2 days, after the spill occurs. Therefore, when cleaning up spills, teams must exercise more caution to protect their workers and the environment. Shipping Concerns: Diluted bitumen is currently transported from the Alberta oil sand reserves. Pipelines are the preferred method of trans- portation, and Dilbit is not considered any more volatile than conventional crude oil. Studies have been done to investigate whether diluted bitumen is more corrosive than other crudes, but no conclusive evidence has shown it to have elevated cor- rosive properties. Health Concerns: Its lighter hydrocarbons are volatile and evaporate out of the Dilbit mixture, when exposed to the environment. These vapors can contain signif cant amounts of benzene and toluene. Ben- zene is a known carcinogen and exposure to it should be limited. Breathing vapors that evaporate from diluted bitumen can result Understanding Diluted Bitumen by 1/C niCKolette Morin Cadet U.S. Coast Guard Academy Cdr GreGory hAll Associate Dean of Academics U.S. Coast Guard Academy 62 Proceedings Summer 2015 www.uscg.mil/proceedings Chemical of the Quarter