Modelling safety assessment process

Toxicologists who use alternative methods in the safety assessment process generally utilize three approaches to help decrease the uncertainty of the predictions when mechanistic understanding is weak. The first is to restrict the use of an alternative method to the same chemical classes that were used to develop the prediction model. This is important because similar materials are more likely to act by the same mechanisms of action. If the materials tested diverge significantly from those used to develop the prediction model, then the reliability of the predictions will decrease. This will occur because the divergent materials may exert effects through different toxic mechanisms that should perhaps be tested in different alternative methods that are sensitive to different chemical parameters and that use different prediction models. 

How do we portray the safety assessment process in a manner that safety novices (e.g. programme managers) can understand There are various frameworks available with the Open University s (refer T840 Block 6 p. 26) hard systems approach (HSA) being particularly useful as a framework for modelling the safety assessment process. 

Sugiyama, H., Hirao, M., Mendivil, R., Fischer, U., Hungerbiihler, K. (2006) A Hierarchical Activity Model of Chemical Process Design Based on Life Cycle Assessment. Process Safety and... 

Due to the importance of safety in process industries various safety and risk assessment methods have been developed to provide the opportunity of considering safety issues in early design stages. Meanwhile several studies have been undertaken to create appropriate implementation tools for developed assessment methodologies (Palaniappan et al, 2002a, Khan and Amyotte, 2004 and 2005). In this paper, inherent safety method and Petri nets modelling have been selected as the safety assessment and implementation tool, respectively. 

Petri net modelling tool can be considered as a suitable implementation tool for risk assessment due to its flexibility and process simulation ability (Vemez et al., 2004). In addition, different feasible process options can be modelled in a Petri net as a super model, and assessed from safety point of view. A Petri net is a directed bipartite graph including places (drawn as circles) and transitions (drawn as bars). Places contain tokens which are shown as dots. The set of arcs are divided into input and output arcs with an arrowhead on their destinations. A transition is called enabled if all input places have at least the same number of tokens as all its output places. An enabled transition fires by removing tokens from input places to output places. Places, transitions and arcs all can be weighted. Weight is an additional feature that can carry critical attribute of related node through the nets (Gu and Bahri, 2002)... 

Glacier-permafrost coupling creates a distinctive hydraulic regime, dominated by transient processes, which must be understood for long term safety assessments. In principle, the problem should be solved by a thermo-mechanically coupled model of the whole ice-water-rock system, driven by an external climate function. As an interim step, we use two separate models, one for... 

In the early stages of preclinical development, metabolite profiling is performed using in vitro systems from animal and human, mainly to identify potential species-dependent metabolism early in the development process and to support the selection of the animal species employed in safety assessment studies. As the compound moves further into development, in vivo animal ADME studies are performed. The compound is usually dosed into a rodent and nonrodent species along with an efficacy model. Metabolism data from the animal studies are then used in species selection for safety assessment to insure that all expected human metabolic transformations will be represented in the animal models used in the safety study. 

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