Chemical carcinogens classification

Risk Index for Mixtures of Hazardous Substances. For the purpose of developing a comprehensive and risk-based hazardous waste classification system, a simple method of calculating the risk posed by mixtures of radionuclides and hazardous chemicals is needed. The method should account for the linear, nonthreshold dose-response relationships for radionuclides and chemical carcinogens (stochastic effects) and the threshold dose-response relationships for noncarcinogenic hazardous chemicals (deterministic effects). 

Carcinogen classification is a one-step, criterion-based process that involves two interrelated determinations evaluations of strength of evidence and consideration of all other relevant information to place chemicals with human cancer potential into hazard categories. 

Cardnogenicity Testing Past, Present, and Futnre Table 3 Main classification of chemical carcinogens 437... 

IRIS is a toxicology data file that contains data in support of human health risk assessment. It is compiled by the US EPA and contains over 500 chemical records. IRIS data, focusing on hazard identification and dose-response assessment, are reviewed by work groups of EPA scientists and represents EPA consensus. Among the key data provided in IRIS are EPA carcinogen classifications, unit risks, slope factors, oral reference doses, and inhalation reference concentrations. 

Figure 7 Illustration of a decision tree generated with C4.5 obtained for the classification of chemical carcinogens in rodents [61]. The classification of 122 chemicals was based on a molecular feature representation that included structural alerts, biological activities in different assays and pathological indicators. The classification leaves at the right hand side of the decision tree are visualized graphically by filled or open boxes. A filled box indicates that the chemicals in that box are classified as rodent carcinogenic open boxes indicate chemicals without rodent carcinogenicity. Note the strong imbalance of the decision tree.

Based upon the ability to interact with genetic material, a general classification scheme of chemical carcinogens has evolved. 

In accordance with the evidence available, different classes for chemical carcinogens have been developed by health authority organizations. Examples ofthe classification of carcinogenic solvents are presented in Table 20.1.3. 

An important application of the results from a battery of in vitro tests is envisioned to be the mechanistic classification of chemical carcinogens. 

It has been shown in this chapter that the DNA-modified electrodes (electrochemical DNA biosensors) already represent very effective and, at the same time, simple, fast, inexpensive, miniaturized, and mass-producible analytical devices for evaluation and classification of modes of genotoxic effects of individual xenobiotic compounds (e.g., chemical carcinogens, pesticides, dmgs, dyes, or reactive radical species), as well as for prescreening of new drugs and newly synthesized chemicals. Moreover, the evaluation of DNA protection capacity of various natural and synthetic chemical substances (antioxidants) is also possible using the detection of DNA damage caused by prooxidants. 

TABLE 5.21 Classification of Carcinogenicity of Chemicals According to the International Agency on Research on Cancer... 

The classification as to whetlier a chemical agent is a carcinogen or a noncarcinogen can help identify whetlier it is a healtli liazard. Both topics are briefly reviewed in this section. More extensive information is provided in Chapter 15. 

Purdy [91] used the technique to predict the carcinogenicity of organic chemicals in rodents, although his model was based on physicochemical and molecular orbital-based descriptors as well as on substructural features and it used only a relatively small number of compounds. His decision tree, which was manual rather than computer based, was trained on 306 compounds and tested on 301 different compounds it achieved 96% correct classification for the training set and 90% correct classification for the test set. 

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