EPA-Expo-Box (A Toolbox for Exposure Assessors)
Direct measurement techniques provide the assessor with chemical concentrations or amounts at the interface between the environment and an individual. This quantity can sometimes be used to estimate the potential dose to an individual. For example, a duplicate diet study is a point-of-contact approach that attempts to quantify the amount of chemical that a person consumes, which is the potential dose for an ingestion exposure. However, to estimate dose at a point on the exposure continuum beyond the potential dose – that is, to estimate applied dose, internal dose, or biologically effective dose – an assessor would need to make other assumptions regarding exposure, such as the amount of chemical absorbed (e.g., across the G.I. tract). The disposition of the chemical following exposure at an external boundary of the body – such as the chemical’s distribution or metabolism within the body – will also need to be accounted for if internal or biologically effective dose are of interest. In general, if dose beyond the potential dose is of interest, the assessor may use methods similar or identical to those described in the Indirect Estimation (scenario evaluation) approach to exposure assessment.