FIELDS M and N 



Columns 45 and 46; 



47 and 48 



made to the discussion of Fields X and Y for a more complete account of coding evaluations and their 

 interpretations. ) 



If a compound causes a given biological response (coded in Fields T and Y) when administered 

 in very small quantities, it is indicative of a more highly sensitive biological system or a more highly 

 active or efficient test compound than if that same response were achieved only by administering more 

 massive doses. Further, when concerned with such sensitive responses, it is usually the case that 

 the dose producing a given response is a more critical factor demanding a nicer distinction than when 

 the biological response is only with large doses. For these reasons, the division of the total range of 

 quantitative values has been basically by logarithmic progressions which provides wide ranges at the 

 upper end of the scale and narrow ranges at the lower end (e. g. , >625 through 2, 525 ppm [Symbol 8] 

 and 0. 04 through 0. 2 ppm [Symbol 2]). 



The total range for any given unit of measure (i. e. , for any given scale of quantities) is not 

 necessarily consistent with total ranges for other units of measure. For example, in Field M, the 

 scale for parts per million (Scale 1) ranges from <. 04 to >2, 525 ppm (= . 000004% to >. 2525%), 

 whereas the scale for per cent weight or volume (Scale 4) ranges from >. 000001% to 100% (= . 01 ppm 

 to 1, 000, 000 ppm) so that the percentage range (Scale 4) is broader than the parts per million range 

 (Scale 1) and the individual symbols for the quantitative values, therefore, describe broader ranges of 

 percentage values (Scale 4) than they do ranges of ppm (Scale 1). The reason for the difference in the 

 case of these two total ranges is simply that an author's use of the unit, ppm, is ordinarily confined 

 to expressing measurements of administered doses when they are of a fine and critical nature. When 

 greater concentrations are used (e. g. , 10, 000, 100, 000, or 1, 000, 000 ppm), an author seldom ex- 

 presses it in ppm, but in percentage concentration. Therefore, it was reasonable to set the limits of 

 the total range for ppm closer than the limits of the total range for percentage and the advantage there- 

 by gained for the ppm scale was a finer division into ranges for the quantitative symbols of the scale. 

 The significant point to be observed is that in two or more scales which are comparable in that the 

 quantitative values of one can be converted to quantitative values of the other (e. g. , 100 ppm can be 

 converted to 0. 01%), the quantitative code symbols do not represent the identical quantitative ranges 

 and are not therefore interchangeable so that whereas 100 ppm is coded with Symbol 6 by the ppm scale 

 (Scale 1), it would be coded with Symbol 5 by the percentage scale (Scale 4). In Field N, Scales 1 

 and 2 do not have identical or even similar range limits. In this case, the two scales represent a 

 continuum and do not overlap at all, essentially for the same reasons as for the difference in ranges 

 of Scales 1 and 4 of Field M. In the case of Scales 1, 2, and 4 of Field N, by spreading the total 

 range across the three, each scale benefits by having a more narrow range for each quantitative 

 symbol than if each scale attempted covering the total range. 



It should be recorded that the scales for those units of measure expressing quantity of pure 

 test compound per unit of test organism or per unit of host organism or host environment (e. g. , mg/kg, 

 mg/sq. ft. , lbs/acre) might have been placed in Field M, since the pure test compound in such cases 

 is understood to be distributed over or through the organism or environment on or into which it is 

 placed and therefore the expressions are indicative of a final concentration of the test compound of 

 which the organism or host environment serves as the diluent. If this were done, the definitions of 

 and distinctions between the uses of the two Fields, M and N, would be altered. The fields would 

 permit distinguishing between (I) any expression of "concentration" (either "initial" or "final") (in 

 Field M) and (II) any expression of "quantity of pure compound disregarding organism or host environ- 

 ment size" (in Field N). This distinction seems of less advantage or significance than the distinction 

 according to whether there can be indicated (1) the administration of the compound at a given concen- 

 tration, although the final total amount is not implied , as opposed to (2) the specific final total amount 

 of compound applied (whether expressed as a total quantity per test organism, host, or host environ- 

 ment or as a total quantity per unit of test organism, host, or host environment). Therefore, this latter 

 distinction has been the basis for definitions of Fields M and N, respectively, and accordingly the 

 scales for quantity per unit of test organism, host, or host environment are in Field N. Thus, with 

 these definitions, when only Field M is coded, it may be assumed that nothing is known except the 

 concentration of the test compound in the preparation administered ; the total amount administered is 

 not known. However, when Field N is coded, either alone or with Field M, there is indicated that 

 actual quantity of test compound administered to the test organism, host, or host environment, accord- 

 ing to which of these three the administration was directly made. 



- 83 - 



