Toxic properties common terms used with

Assays that detect the ability of chemical carcinogens or UV or ionizing radiations to induce unscheduled DNA synthesis, or DNA repair, are also commonly used. In one of these, autoradiography is used to measure the incorporation of tritiated thymidine into the DNA of cells treated with these carcinogens. All the assays mentioned above are commonly used at the same time to detect the geno-toxic properties of chemicals or radiation in what is referred to as a battery of tests. This battery of tests usually constitutes what is termed a primary screen... 

Numerous relationships exist among the structural characteristics, physicochemical properties, and/or biological qualities of classes of related compounds. Simple examples include bivariate correlations between physicochemical properties such as aqueous solubility and octanol-water partition coefficients (Jtow) and correlations between equilibrium constants of related sets of compounds. Perhaps the best-known attribute relationships to chemists are the correlations between reaction rate constants and equilibrium constants for related reactions commonly known as linear free-energy relationships or LFERs. The LFER concept also leads to the broader concepts of property-activity and structure-activity relationships (PARs and SARs), which seek to predict the environmental fate of related compounds or their bioactivity (bioaccumulation, biodegradation, toxicity) based on correlations with physicochemical properties or structural features of the compounds. Table 1 summarizes the types of attribute relationships that have been used in chemical fate studies and defines some important terms used in these relationships. 

The lanthanide series of metals includes the 15 elements with atomic numbers 57-71, plus yttrium (atomic number 39). The lanthanides occur in the earth s crust at concentrations exceeding some commonly used industrial elements making the term rare earths something of a misnomer. For example, yttrium, cerium, lanthanum, and neodymium are present in the earth s crust at higher concentrations than lead. Of the 15 lanthanides, only promethium does not occur in nature - it is a man-made element. All of the lanthanides have similar physical and chemical properties. Because of similarities in their chemistry and toxicity, the characteristics of the lanthanides are often described as a group. Within the lanthanide group, however, there are differences between the toxicity of the individual lanthanide elements and their compounds. 

In the read-across or analogue approach, endpoint information for one chemical is used to make a prediction of the endpoint for another chemical, which is considered to be similar in some way. In principle, read-across can be used to assess physicochemical properties, environmental fate, and (eco)toxicity effects, and it may be performed in a qualitative or quantitative manner. A one-to-one read-across is an ad hoc comparison based on the similarity between two chemicals. Read-across carried out between three or more chemicals can lead to the formulation of generalizations about the group, and eventually to establish that a common substructure can be associated with a SAR. Although the distinction between SAR and read-across may appear vague, the term SAR usually refers to an approach that has been subjected to some degree of statistical validation, and thus to a more formalized approach than read-across. 

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