Section 1. IDENTIFICATION AND HAZARD SUMMARY
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What happens when crude oil is released into the environment?
Routine human activities (e.g., extracting, processing, refining), accidental releases and natural features such as oil seeps and tar pits release crude oil into the environment. Crude oil may be spilled on land, into fresh water or into seawater. The physical and chemical characteristics of the oil will interact with the physical and biochemical features of the habitat where a spill occurs. Once released into the environment, the major migration pathways of crude oil chemical constituents include the following [CB&1, 2015]: •
Evaporation, volatilization and dispersion into the air;
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Infiltration into soil in the immediate vicinity of the release;
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Direct surface release or overland runoff from release location to streams, rivers, lakes, coastal water areas, outer harbours, open water, ditches, wetlands and storm/ sanitary sewers; and
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Transport in groundwater, after leaching through soil saturated with crude oil.
Guidance for the Environmental Public Health Management of Crude Oil Incidents
in temperate climates [ITOPF, 2014a; ASM, 2011; NOAA, 2014]. Components of crude oil, when released into the environment, will partition into various environmental compartments. The lower molecular weight components may dissolve in water or volatilize to the atmosphere. Intermediate fractions may float and spread out on water, where they may form emulsions and/or adsorb to soil and sediment. The viscous, heavy components may agglomerate and float or sink in water or adhere to soil and sediment. The rate at which partitioning occurs depends not only on the nature of the crude oil but also on the severity of the weathering processes it encounters [ITOPF, 2014a; ASM, 2011]. When components of crude oil disperse, they may undergo further chemical and physical transformations. Constituents that partition to the air interact with hydroxyl radicals, ozone and other free radicals in the atmosphere and thus are subject to indirect photo-degradation. Atmospheric half-life ranges from 0.4 days (e.g., n-dodecane) to 6.5 days (e.g., benzene) [ASM, 2011; NOAA, 2014].
The physical and chemical changes that spilled oil undergoes over time are collectively known as weathering [ITOPF, 2014a; HSDB, 2011; ASM, 2011; API, 2011a; API, 2011b]. These include evaporation, dispersion, dissolution, oxidation, emulsification, spreading, biodegradation, and sedimentation, including oil-particle aggregate formation. The individual processes causing these changes may act simultaneously, with their relative importance varying in time. Together, these processes affect the behaviour of the oil and determine its ultimate fate. In general, those oil components with a boiling point below 200°C will evaporate within 24 hours
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Version 1.0 – August 2018
