With few exceptions, the toxicity of solid formulations was consider- 

 ably lower than that of their liquid counterparts. The greater toxicity of the 

 liquid formulations can probably be attributed to the orgamic compounds used 

 as solvents and diluents. The carrying agents used in the preparation of solid 

 formulations are inert clays which by themselves have no effect on the animals 

 tested. Differences in the availability of the active ingredients in liquid and 

 solid formulations may also be a factor. 



The above compounds are listed according to their decreasing toxi- 

 city to the two species, but the ranking is somewhat tentative because the bio- 

 assay results may be affected by size of test animals, temperature, etc. For 

 instance, the table suggests that pesticides are more toxic to smaller indivi- 

 duals. The effect of temperature on toxicity is indicated by the significantly 

 higher mortadity of Gulf killifish (Fundulus grandis) when exposed to 70 p.p.b. 

 dieldrin at 21° C. than when exposed to the same concentration at 17° C. 



Mortality of Gulf killifish exposed to 70 p.p.b. 

 of dieldrin at two temperatures. 



The probable importance of turbidity on the toxicity of pesticides 

 is shown by a test in which the toxicity of a 50 p.p.b. solution of technical 

 grade DDT to pinfish (Lagodon rhomboides) was notably reduced by the addi- 

 tion of 4 grams of inert clay to simulate silt. 



52 



