Table 11.--DDT and methoxychlor residues stored after feeding rats 
for different periods and at various rates1 (16, 17) 
Insecticide and 
weeks fed 

Residues stored in-- 
1 Storage at 10-20x intake for DDT and 0.01-0.1x intake for meth- 
oxychlor. 
Methoxychlor has been known since 1944, 
Despite its safety, high official tolerances on 
agricultural commodities (up to 100 p.p.m. as 
compared with 7 p.p.m. for DDT), and potential 
freedom from the problems of environmental 
contamination, it has had only limited usage. 
Annual consumption in the United States is 
estimated at less than 5 million pounds as 
compared with 70 million pounds for DDT. 
The U.S. Department of Agriculture Agricul- 
ture Handbook 120, "Insecticide Recommen- 
dations" 1961, lists only 81 uses for methoxy- 
chlor as compared with 334 for DDT, Although 
the lower overall insecticidal effectiveness and 
more particularly the higher price (about $1 
per pound as compared with $0.20 for DDT) 
may explain methoxychlor's relative unpopu- 
larity, it is evident that methoxychlor should 
be the preferred material in any application 
where storage in animal tissues is a factor. 
This has in fact been achieved only inthe case 
of direct applications to livestock and appli- 
cations to alfalfa and other hay crops intended 
for dairy cattle feed, where it has been shown 
that methoxychlor is not excreted in milk. 
In conclusion, it seems clear that the chemist 
and toxicologist are capable of tailoring in- 
secticidal molecules, incorporating almost any 
combination of desirably selective properties. 
However, there remains the equally important 
problem of insuring that these superior mole- 
cules replace less desirable compounds in 
practical pest control. This can be encouraged 
best through appreciation of the biochemical 
and ecological dimensions of the living en- 
vironment into which the pesticide is projected 
and by widespread utilization of the principles 
of integrated pest control. This symposium is 
a significant step in bringing us closer to this 
goal. 
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Benjamin, E,, R, Metcalf, and T, Fukuto, Jour, 
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Brown, A, W, A, Insect Resistance in Arthopods, 
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