Branches of Toxicology

Based on the field of specialization, toxicology is categorized into branches. These branches are often interrelated and could be listed as  

The nanomaterials thus manufactured in different industries—particularly drugs and pharmaceuticals— might pose risks to human health and other organisms due to their composition, reactivity, and unique size. Nanotechnology research and development, particularly in medical research, work at the micro- and nanoscale levels to develop new drug delivery methods, therapeutics, and pharmaceuticals. In such areas of research it is equally important to consider the potential interactions of nanomaterials with the environment and the associated risks. This involves studying the effects of natural nanoparticles in the air and soil, life cycle aspects of manufactured nanomaterials, and their fate and transport. Risk assessment also includes studies 

While there are differences in the methods of data generation from one branch to another, all branches are interrelated to provide complete data about the toxicity and safety of a candidate test chemical substance vis-a-vis human safety. Toxicity of a chemical is the result of several reactions and interactions between the candidate chemical and its metabolites and the cellular receptors. These include enzymes, glutathione, nucleic acids, hormone receptors, and the like. The degree of toxicity of a chemical could be explained as follows  

Ar = the specific affinity of the receptor for the toxic chemical C. The toxicity of a chemical can also be expressed as toxicity = k (C) (R) Ac, where toxicity is dependent upon C, R, and Ac C = concentration of the candidate chemical in the tissue R = concentration of the endogenous receptor of the tissue Ac = affinity of the receptor for the chemical 

The toxicological evaluations related to human safety of chemical substances are a very complex process involving the determination of the intrinsic toxicity and hazard of the test chemicals. Subsequently, this evaluation leads to determining and establishing a no observed effect level (NOEL) the highest dose level tested experimentally that did not produce any adverse effects. This dose level then is divided by a safety factor to establish an acceptable daily intake (ADI) of the candidate chemical substance. The ADI value is normally based on current research and 

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The term ecotoxicology has been defined as the branch of toxicology concerned with the study of toxic effects, caused by natural or synthetic pollutants, to the constituents of ecosystems, animal (including human), vegetable and microbial, in an integral context [14]. 

This requires a sound mechanistic base to be successful. It is this mechanistic base that comes within the scope of biochemical toxicology, which forms the basis for almost all the various branches of toxicology. 

The explanation of the pharmacokinetics or toxicokinetics involved in absorption, distribution, and elimination processes is a highly specialized branch of toxicology, and is beyond the scope of this chapter. However, here we introduce a few basic concepts that are related to the several transport rate processes that we described earlier in this chapter. Toxicokinetics is an extension of pharmacokinetics in that these studies are conducted at higher doses than pharmacokinetic studies and the principles of pharmacokinetics are applied to xenobiotics. In addition these studies are essential to provide information on the fate of the xenobiotic following exposure by a define route. This information is essential if one is to adequately interpret the dose-response relationship in the risk assessment process. In recent years these toxicokinetic data from laboratory animals have started to be utilized in physiologically based pharmacokinetic (PBPK) models to help extrapolations to low-dose exposures in humans. The ultimate aim in all of these analyses is to provide an estimate of tissue concentrations at the target site associated with the toxicity. 

An increasingly useful branch of toxicological chemistry is the one dealing with quantitative structure-activity relationships (QSARs). By relating the chemical structure and physical characteristics of various compounds to their toxic effects, it is possible to predict the toxicological effects of other compounds and classes of compounds. 

Both branches of toxicology are concerned with the study of the fate of chemicals and the assessment of the toxicity of chemicals. Nevertheless, a clear distinction exists between these subjects and this difference arises because man is not an experimental species. The environmental toxicologist can often study the species at risk or, alternatively, a very closely related species. However, in order to identify human hazards and evaluate the risks to humans, the mammalian toxicologist must resort to the use of biological models. 

The branch of toxicology focusing on impacts of chemical pollutants in the environment on biologiccd orgcmisms. 

Agency for Toxic Substances and Disease Registry Division of Toxicology/Toxicology Information Branch 1600 Clifton Road NE, E-29 Atlanta, Georgia 30333... 

Food and Drug Administration (1966). Guidelines for Reproduction Studies for Safely Evaluation of Drugs for Human Use. Drug Review Branch, Division of Toxicological Evaluation, Bureau of Science, Food and Drug Administration, Washington, D.C. 

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