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|LC50, 50% Lethal Concentration|
This is closely related to the LCLo value which is the lowest concentration reported to have killed animals or humans.
Both LC50 and LD50 values state the animal used in the test. This is important because animal toxicity studies do not necessarily extrapolate (extend) to humans. For example, dioxins (of Love Canal, Times Beach, Sveso and Agent Orange fame) are highly toxic to guinea pigs and ducklings at extremely low levels, but have never been conclusively linked to a single human death even at very high levels of acute (short term) exposure. However, it is best to err on the safe side when evaluating animal toxicity studies and assume that most chemicals that are toxic to animals are toxic to humans.
Typical units for LC50 values are parts per million (ppm) of material in air, micrograms (10-6 = 0.000001 g) per liter of air and milligrams (10-3 = 0.001 g) per cubic meter of air (see volume units and mass units).
New testing regimes, such as the Acute Toxic Class (ATC) and Up Down methods, have been developed which use fewer animals and provide more reliable toxicity class assignments than the traditional LC/LD50 methods. See the links under Further Reading below.
Pay close attention to the permissible exposure level (PEL) instead. This is a more realistic determination of the maximum safe exposure to a material and is usually based on the known effects of the chemical on humans rather than laboratory animals.
Get your D.O.T. hazardous material placards & labels at Safety Emporium.
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