Acute—An event occurring over a short time, usually a few minutes or hours. An acute effect happens within a short time after exposure. An acute exposure can result in short-term or long-term health effects. Acute toxicity to aquatic organisms is estimated from short exposures, usually 24, 48, or 96 hours and lethality (death) is the typical endpoint. Results from acute toxicity tests usually report the lethal concentration of the toxicant that causes death to 50% of the test organisms (LC50). The lower the LC50 value the greater the toxicity of the toxicant.
Bitumen—A mixture of hydrocarbons that is too viscous to flow under ambient conditions. Commercial quantities are recovered by thermal processes.
Chronic—An event occurring over a long period of time, generally weeks, months, or years. Chronic exposures occur over an extended period of time or over a significant fraction of an organism’s lifetime. Chronic toxicity to aquatic organisms can be estimated from partial life-cycle tests of relatively short duration depending on the organism (i.e., 7 – 21 days) and growth and reproduction are the typical endpoints. Results from chronic toxicity tests are reported as the toxicant concentration that causes a given effect.
Commonly transported crude oils—The oils carried by most transmission pipelines in the United States. Available data show that currently >70% of these are light and medium crude oils.
Conventional oil—Oil that is produced by drilling and pumping from a naturally permeable, subsurface reservoir.
Crude oil—Naturally occurring, unrefined petroleum hydrocarbons extracted from the earth to serve as feedstock for the petroleum industry.
Diluted bitumen—Bitumen diluted with lighter hydrocarbons or a combination of light hydrocarbons such as natural-gas condensate, lighter crude oil, or synthetic oil, such that its viscosity is reduced.
Diluted heavy oil—Heavy oil that is diluted with lighter hydrocarbons such as natural-gas condensate, lighter crude oil, or synthetic oil, such that its viscosity is reduced.
Gas condensate—A low-density mixture of hydrocarbon liquids obtained by condensing the less-volatile components of raw natural gas.
Heavy crude oil—A naturally occurring, unrefined petroleum product with a density greater than 0.93 g/cm3 or an API gravity less than 20.
High molecular weight petroleum compounds—Compounds with a molecular weight greater than about 250 Daltons; typically these compounds are viscous liquids or solids at ambient temperatures.
Light crude oil—A naturally occurring, unrefined petroleum product with a density ranging from 0.80 to 0.85 g/cm3 or an API gravity ranging from 35 to 45.
Low molecular weight petroleum compounds—Compounds with a molecular weight lower than about 250 Daltons; typically these compounds are liquids at ambient temperatures.
Medium crude oil—A naturally occurring, unrefined petroleum product with a density ranging from 0.85 to 0.92 g/cm3 or an API gravity ranging from 36 to 21.
Sublethal—Toxicant is below the concentration that directly causes death. Exposures to sublethal concentrations of a toxicant may produce less obvious and measureable effects on behavior, molecular, biochemical, cellular and/or physiological function (e.g., growth and reproduction) and histology of organisms.
Synthetic crude—Oil produced from bitumen by physical and chemical processes less elaborate than those used in full-scale refineries and implemented near the site of production.
Transmission pipeline—A continuous pipe used to transport oil and petroleum products from gathering points to storage or distribution points. It is distinct from smaller, shorter pipelines used to collect oil from individual wells or to distribute to points of consumption.
Unconventional oil—Oil that is produced by unconventional means, including thermal separation of non-liquid bitumen from a host rock and hydraulic fracturing of impermeable reservoirs or source rocks.
Undiluted heavy oil—Heavy oil that is transported without dilution. It may be heated to facilitate transport.
Upgraded bitumen—Bitumen that has been subject to some refinement to remove or convert some of the more recalcitrant components. It is also an intermediate in the production of synthetic crude oil.