A widely accepted protocol has yet to be established to measure human exposure to EDCs. However, mathematical models can be devised according to EPA guidelines for exposure assessment.
The predominant matrices for measuring internal doses include blood, breast milk, adipose tissue, and muscle tissue. Although obtaining tissue samples is quite invasive, breast milk, blood, and excretion product samples are readily obtainable. Both immunoassays and immunoaffinity chromatography have been successfully used in conjunction with classical instrumental analysis (GC, LC, HPLC, and MS) in the analysis of biological fluids.
In determining human exposure levels, internal dosing provides marked benefits over theoretically based models. Most notably, internal dosing integrates over all exposure routes and includes dosing from internal sources (dosing from lipid soluble EDCs for example). Also, readily metabolized compounds can be detected through the analysis of excretion products (urine) for characteristic metabolites. Exposure can then be estimated from the levels of metabolites in the excretion products.
There are, however, limitations of internal dosing. For example, the methods neglect information about sources and routes of exposure. In addition, information regarding the nature of exposure and timing of metabolism, transport, storage, and elimination of chemicals is important. Internal dosing does not account for these variables. Internal dosing measurements are also difficult to obtain for chemicals with short half-lives, unless the chemicals have reached steady state levels in the tissue of interest.