(interindividual variability), the uncertainty in extrapolating animal data to the human population (interspecies uncertainty), the uncertainty in extrapolating from data obtained in a study involving less-than-lifetime exposure (extrapolating from subchronic to chronic exposure), the uncertainty in using LOAEL data rather than NOAEL data, and the uncertainty associated with extrapolation when the database is incomplete.¹⁶ A UF of 10 is considered to be a health-protective default value to be used when little is known about a particular source of variability or uncertainty or when information on a relevant health effect is lacking. As additional research becomes available, UFs change as indicated by the new information.

VGI:

volume of gastrointestinal tract.

V_max:

describes, in units of milligrams per hour, the maximal capacity or velocity for binding or transport, such as binding or transport of iodide by the NIS.

V_maxC:

describes, in units of milligrams per hour per kilogram of body weight, the maximal capacity or velocity for binding or transport scaled by body weight according to the equation: V_max (mg/hr) = [V_maxC (mg/hr per kg)][body weight (kg)]^0.70.

VSk:

volume of skin.