Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:8:p7
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 8 (pt 7/7)
Character Range: 3054464–3056298

intake or acceptable risk. The TRV may be associated with either a threshold (i.e. ADI, TDI, TC or reference dose) or non-threshold (i.e. slope factor or unit risk) doseresponse relationship.
Uncertainty analysis is a methodology that takes into account domain knowledge and its limitations in qualifying or quantifying (or both) the uncertainty in the structure of a scenario, structure of a model, inputs to a model and outputs of a model.
Uncertainty is a lack or incompleteness of information or knowledge. In risk assessment, uncertainty has been defined by IPCS (2004) as 'imperfect knowledge concerning the present or future state of an organism, system, or population under consideration'.
Unit risk is the plausible upper-bound estimate of the probability of a response from a chemical over a lifetime expressed in units of concentration for a specified medium.
Uptake is the amount of contaminant that enters the body through a barrier such as the skin, lungs or gut lining. Uptake is generally less than intake because not all the contaminant that enters the lungs or gut, or contacts the skin, is absorbed.
Vadose zone is the portion of the sub-surface between the water table and the ground surface, also termed the unsaturated zone. Soil pore space in the vadose zone is only partially occupied by water, which is held in place by capillary forces and adhesion to soil particles.
Variability describes true differences in attributes or values due to diversity or heterogeneity.
Vulnerability refers to human populations at higher risk due to environmental factors. Examples of vulnerability factors include age, existing or past illness, poverty and other social determinants, smoking, poor nutrition, poor sanitation, behaviour more often associated with severe or profound intellectual disability (for example, pica).