Human Equivalent Concentration (HEC) or Human Equivalent Dose (HED)
Human Equivalent Concentration (HEC) or Human Equivalent Dose (HED) : (a) The human concentration (for inhalation exposure) or dose (for other routes of exposure) of an agent that is believed to induce the same magnitude of toxic effect as the experimental animal species concentration or dose. This adjustment may incorporate toxicokinetic information on the particular agent, if available, or use a default procedure, such as assuming that daily oral doses experienced for a lifetime are proportional to body weight raised to the 0.75 power. [IRIS, 1999: Glossary of IRIS Terms]; (b) [human equivalent concentration] Exposure concentration for humans that has been adjusted for dosimetric differences between experimental animal species and humans to be equivalent to the exposure concentration associated with observed effects in the experimental animal species. If occupational human exposures are used for extrapolation, the human equivalent concentration represents the equivalent human exposure concentration adjusted to a continuous basis. [USDOE, 2000: RAIS Glossary]; (c) [human equivalent dose] A dose that, when administered to humans, produces an effect equal to that produced by a dose in animals. [REAP, 1995: Residential Exposure Assessment Project] [USEPA, 1997a: EPA Terms of Environment] [USDOE, 2000: RAIS Glossary]
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