Kinetic modeling, hazard evaluation

Laboratory rodents are the animal models most commonly used to identify hazards in reproductive toxicity. Rodents are used because they are small animals, the assay cost is moderate and there is a large database of toxicology information on these species (e.g., dose-response, metabolism, kinetics, etc.). The rat has proven to be a good model for human reproductive hazard evaluation (Francis et al., 1990). 

A successor to PESTANS has recently been developed which allows the user to vary transformation rate and with depth l.e.. It can describe nonhomogeneous (layered) systems (39,111). This successor actually consists of two models - one for transient water flow and one for solute transport. Consequently, much more Input data and CPU time are required to run this two-dimensional (vertical section), numerical solution. The model assumes Langmuir or Freundllch sorption and first-order kinetics referenced to liquid and/or solid phases, and has been evaluated with data from an aldlcarb-contamlnated site In Long Island. Additional verification Is In progress. Because of Its complexity, It would be more appropriate to use this model In a hl er level, rather than a screening level, of hazard assessment. 

A study of the kinetics of thermal decomposition reactions using pentaerythritol tetranitrate(PETN), a high explosive, as the model substance was first conducted by SC-DSC. In this study, information was obtained that was relative to the characteristics of the DSC technique. However, the question as to how the results of analyses of this type were useful for practical work arose, and studies in this area were stopped. Subsequently, studies have proceeded on the evaluation of hazards by collecting as much data on self-reactive substances as possible. 

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