The CBR approach in measuring toxicity of narcotic chemicals
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Over the past years, the risk assessment of organic chemicals such as Persistent, bioaccumulative and toxic compounds (PBTs) and Persistent organic pollutants (POPs) has received growing attention because of their proprieties: persistence, bioavailability and bioaccumulation. In order to predict the toxicity levels of organic chemicals, it is important to know their chemical structure and the modes of actions. Quantitative structure-activity relationships models (QSARs) were used to classify narcotic chemicals. However, one of the problems in ecological risk assessment of organic chemicals is the determination of bioavailability from the ecosystem to organisms and mostly, from organism to the target (organ or cells). It was shown that the bioavailability is related to biological and physical properties of the target sites, such as lipid and protein contents of membranes. The Critical Body Residue Approach (CBR) or Lethal Body Burden (LBB) was developed in order to estimate critical effect levels of narcotic chemicals in the organism and thereby, to make an estimation of the true level of risk. Making real estimations means also developing models that are as similar to the organism as possible, in terms of biological structures and partition dynamics. The more the model reflects the organism, the more precise and accurate the estimations will be. Undoubtedly, future researches have to be done. Models should be improved and the characterization of compartments and proteins need particular attention because of the high variability as was already mentioned. It would be useful to improve already existing models and develop new ones in order to have a wider representation of important tissues. Proteins and their own proprieties should be integrated in these models and described using specific parameters as was already done with lipids.