Biokinetic models construction

Figure 2.19. Flowchart of the construction of unstructured biokinetic models as a consequence of joint activity between kinetic work and stoichiometry. (Adapted from Reels, 1980a. With permission of John Wiley Sons, Inc.).

Much of the interest in using predictive modeling of human Pb exposures concerns mechanistic, i.e., biokinetic, models. Biokinetic models differ from site-specific or multisite ad hoc/slope factor models in a number of important ways. Eirst, they are constructed (by definition) within a computational and biological/kinetic framework. That framework specifies inclusion of all identified parameters representing mechanisms by which environmental Pb is deposited in and removed from human organs and tissues. Mechanistic models are structured to be much more complex than the regression models... 

The evolution of biokinetic models of Pb exposures in human populations allows classification into models that were useful in their time but are now mainly of historical interest and those currently enjoying wide use. This evolution of contemporary exposure models has tracked scientific developments in the field of Pb toxicokinetics. Currently employed biokinetic models can be classified into those having different mathematical construction and predictive conceptualization underlying the model. One of the widely used models is the classical compartmental type. Others are PB-PK models. 

Current biokinetic models differ in their flexibility for use in other than stable, (near) steady-state Pb exposures of human risk populations. The lEUBK is only operative in cases where Pb exposures are stable and long term. By contrast, the O Haherty PB-PK model is constructed to reflect acute or episodic Pb exposures. Current biokinetic models also differ in the age ranges of exposed populations to be modeled. The lEUBK model is for children up to 84 months old. The PB-PK models are basically hfetime in their application. 

Current Pb exposure modeling through biokinetic approaches uses either classical compartment constructions with some PB-PK features or frameworks which are largely PB-PK in form. Evolution of these models from earlier precursors was greatly assisted by growing parallel knowledge and a growing literature about Pb biokinetics and other quantitative features of... 

As is the case with the model s biokinetic component, the lEUBK model was constructed to reflect steady-state Pb toxicokinetics and therefore relatively stable Pb exposures, preferably at least a year or so. Consequently, the model does not permit simulations of PbB levels where Pb exposures are either intermittent or acute. 

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