Table 1. Determination of Priority for Testing' 



Predictability of toxicological 

 characteristics of chemical substance 



High 

 0) 



Medium 

 (2) 



Low, 

 (3) L 



Widespread distribution (4), substan- 

 tial amounts released 



Widespread distribution (3), small 

 amounts released 



Localized distribution (2), substan- 

 tial amounts released 



Localized distribution (1), small 

 amounts released 



To determine final priority number, multiply the appropriate number above by 

 the following vulnerability factor for the receiving system: high = 3, med- 

 ium = 2, low = 1, (From an approach for determining priority testing in 

 Principles for Evaluating Chemicals in the Environment , National Academy of 

 Sciences, Washington, DC 1975, 453 pp.) 



High number indicates high priority. 



The matrix is designed to determine relative priorities within a single 

 decisionmaking area. For simplicity, the number of categories has been kept 

 to a minimum. For maximum safety, it would be well to use a slightly higher 

 than probable consideration of impact in making all the decisions. Further- 

 more, because of the simplicity of the matrix, it should be used only as a 

 guide rather than as an absolute and rigid system of priority determination. 

 Specific problems related to a particular chemical, region, or ecosystem 

 must be introduced by the user. Failure to do so will almost certainly result 

 in an inadequate definition of the problem. 



In Principles for Evaluating Chemicals in the Environment , the presump- 

 tion is that the biological effect of linear alkyl sulfonates or other deter- 

 gents is minimal, but the effect of chlorinated hydrocarbons and other fat- 

 soluble materials is very severe. The approach is coupled with a materials- 

 balance analysis so that one can distinguish between certain chemicals used 

 in small amounts in very small regions and chemicals used in large amounts 

 globally. By combining the materials-balance information for a chemical with 

 biological-effects information, it is possible to obtain a number that indi- 

 cates relative priority in conducting a hazard evaluation of the chemical. 



163 



