FIELD T-2 

 Columns 58, 59, 60, and 61 



distinguishing potencies of test compounds for causing death, implied by the terms "chronic" and 

 "acute", as defined hereafter. Having Symbol 112, in addition to 1 1 1 and 11, permits Field T-2 to 

 have uniquely, in the case of coding "death", the general function of distinguishing the degree of 

 severity of action (the degree of potency ) of the test compound. 



When a test compound, at a given level of administration, causes death only after a considerable 

 time, the response is referred to as "chronic"; if, at a given dose, the test compound causes death in 

 a relatively short time, the response is said to be "acute" or severe. Very commonly, when these 

 determinations are made for a compound, they are spoken of as "chronic toxicity" and "acute toxicity" 

 determinations. In spite of the frequency of usage of the latter terms in certain biological fields of 

 testing, they are somewhat unfortunate in that the word "toxicity" is not itself a synonym of "death". 

 The fact that it can refer to any of a large number of non- lethal detrimental effects frequently leads to 

 confusion especially with coders who have had no reason to use the terms, or encounter the terms used, 

 synonymously with "death" determinations. 



Drawing an arbitrary line at the 24-hour point, then, any death produced within the shorter time 

 period (24 hours or less) might be referred to as "acute toxicity", whereas death produced only after 24 

 hours is referred to as "chronic toxicity". This is somewhat modified, however, by the provision that 

 when death is caused from a single administration (not continuous and not multiple), the severity should 

 be considered as acute regardless of the time taken to kill (<24 hours or >24 hours). Note that these 

 distinctions are made by the CBCC; there are probably no such universally accepted exact demarcations 

 between acute and chronic toxicity. However, having Symbol 112 does have one important "cataloging" 

 advantage; it makes a convenient coding distinction whereby all compounds of higher potency for lethal 

 action can be separated from those having lower potency for lethal action. Potency of a compound for 

 causing a given response such as death is always indicated in Field Y (or indicated by the combined 

 coding of Field Y and Field M or N). The significance of making a gross potency distinction in Field 

 T-2 is that, by having done so, the Field Y evaluation may subsequently be made on the basis of only 

 one or the other of the two broad categories of lethal potency. In other words, evaluation of Field Y 

 Is an expression of either the "degree of acuteness of lethal potency" or the "degree of chronicity of 

 lethal potency", rather than merely the "degree of lethal potency". 



In the fifth mimeographed edition of the Code, Symbol 1 1 was defined appropriately merely as 

 general toxicity (and, under it, were organized the various more specific toxicities such as death [111 

 and 112], local toxicities [113], systemic toxicities [114], etc. ). In the sixth edition and in the 

 present list of Field T-2, Symbol 11 has been utilized to code death specifically rather than to code 

 general toxicity, a rather exceptional arrangement which exists only for the historical reason just 

 explained. The present definition of Symbol 1 1 provides another distinction to be made for death (just 

 as Symbol 1 12 provides a distinction as described above) which is not made by any other field, though 

 it resembles the type of information coded in Field S-3. It is a distinction that ordinarily need not be 

 made if administration is made separately to each individual tested (in which case the dosage given to 

 the individual is ordinarily determined), but is a distinction that needs to be made when administration 

 is to a group or population of individuals or when it is to one or more animals consuming the test 

 compound ad lib. In the latter situations, acute toxicity may be expressed only in terms of the time 

 taken to kill the organisms tested under the conditions of administration, but there is no determination 

 of the amount of the compound the individual actually consumed or contacted. This latter information 

 is of greater basic biological significance than merely information about the amount needed in a field 

 spray or in a food material, or in. an aerosol, etc. , to accomplish a given percentage of kill. When- 

 ever the data tell nothing more than the lethal amount applied to a population (without having determined 

 the amount received by each individual), Symbol 11 is used and the dose coded in Field M or N is the 

 dose administered to the group, population, or environment (food, etc. ). Symbol 111 is used only 

 when the amount received by each individual and causing death in that individual is determined and 

 coded in Field M or N. 



This last distinction is only made when death occurs in 24 hours or less ( acute toxicity, Symbol 

 111 or 11). For death caused only after 24 hours ( chronic toxicity, Symbol 112), no similar distinction 

 is made as to whether or not the dose received by each individual has been determined. An additional 

 symbol might be added to make the latter distinction, but it is not a refinement the CBCC has found 

 necessary in the case of "chronic" lethal effects. 



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