84 CIRCULAR 9 7 7, IT. S. DEPARTMENT OF AGRICULTURE 



gross toxic effect. In solution laboratory animals can tolerate single 

 dermal exposures of about 3 grams per kilogram of body weight. 

 Calves less than 1 month old, which are general!}' the most susceptible 

 livestock, can tolerate emulsion or wettable-powder sprays containing 

 8 percent, or more of DDT. 5 Treatment of cattle with a 2-percent 

 DDT spray 10 times at 2-week intervals caused no clinical symptoms 

 of poisoning. 



On the basis of acute-toxicity data and the wide use experience in 

 the direct treatment of persons, as for louse control, and in residual 

 spraying in homes, DDT as recommended for controlling insects 

 affecting man creates no undue acute hazard. However, the danger 

 to guard against is the chronic hazard that may result from its im- 

 proper and careless use, particularly in food contamination. The 

 Food and Drug Administration has reported that 5 p. p. m. of DDT 

 in the diet of laboratory animals will in time cause some liver damage. 

 The insecticide is readily stored in fatty tissues when consumed or 

 absorbed through the skin. It is slowly eliminated from the body. 

 DDT is also excreted in the milk of animals when applied to them or 

 when consumed in the diet. The time required for DDT to be 

 eliminated from the animal system depends on the amount stored, 

 but it may be several months to a year. It should therefore be used 

 in such a manner as to avoid food contamination. 



Extensive investigations have shown that, if improperly used or if 

 applied in excessive amount, DDT may cause serious harm to fish, 

 birds, mammals, and other beneficial organisms. 



Special Precautions in Using DDT 



Do not use DDT emulsions in waters containing fish. The insecticide is 

 much more toxic in this form than in dusts, oil solutions / or suspensions. 



DDT in oil solutions at the rate of 0.3 pound per acre may destroy fish 

 and other aquatic life. Do not exceed this rate of application in bodies 

 of water containing fish. 



Do not apply in excess of 2 to 4 pounds of DDT per acre in residual 

 sprays to vegetation or the ground, since higher dosages may prove harmful 

 to birds, mammals, or other beneficial life. 



Do not use inside dairy barns or milk rooms. 



PYRETHRUM AND ALLETHRIN 



Pyrethrum and allethrin, and the synergists piperonyl butoxide, 

 sulfoxide, sesame oil, and propyl isome used with these insecticides, are 

 all low in toxicity to animals from the standpoint of both acute and 

 chronic exposure either orally or dermally. 



When used as recommended for insect control these insecticides 

 create no undue hazards. However, the general precautions on 

 pages 82-83 should be followed. 



METHOXYCHLOR 



Methoxychlor is related to DDT chemically but is much less toxic 

 to animals both acutely and chronically. It is perhaps the least toxic 



5 Information on the toxicity of the various insecticides to livestock was ob- 

 tained from "Toxicity to Livestock," by Radeleff, R. D., Bushland, R. C, and 

 Clabom, PI. V., in Insects, Yearbook of* Agriculture 1952, pp. 276-283, and from 

 unpublished data obtained at the Kerrville, Tex., laboratory. 



