Fenthion (Bayer 29493, Mercaptophos, Baytex, Lebaycid) [0,0-Dimethyl 
O-(4-(methylthio)-m-tolyl) phosphorothioate | 
P32_labeled fenthion was applied dermally and intramuscularly to dairy 
cows. Residues of the fenthion sulfoxide and/or sulfone and/or sulfone of 
the oxygen analog, as well as the oxygen analog, were present in urine. 
Dimethyl phosphate and dimethyl phosphorothioate, and an unknown thought to 
be desmethyl fenthion, were also found in the urine. Similar findings were 
observed in feces. In edible tissues, results were similar except that 
phosphorothioic acid was the predominant hydrolysis product (812). 
In suicides with fenthion, 3-methyl-4-mercaptophenol has been identi- 
fied in stomach contents and in urine by means of TLC, paper chromatography, 
and ultraviolet spectra. No dimethyl phosphorothioate was observed (282). 
When rats, houseflies, the German cockroach, boll weevil, and cotton 
plant were exposed to P32_1abeled fenthion, five compounds were found in 
different proportions (165). 
Sulfoxide appeared as the chief metabolite of fenthion when the latter 
was applied to bean plants. In addition to the sulfoxide, the sulfone, and 
the sulfoxide and sulfone of the phosphate, and the S-methyl isomeride were 
also found. The latter was also oxidized to the corresponding sulfone and 
sulfoxide (479, 1084). When applied to cabbage and tea plants, metabolism 
was rapid. The sulfoxide and sulfone were the main metabolites although 
some oxidation of thiophosphate to phosphate also occurred (1413). On rice 
plants, only about 10% of the applied material remained after six hours. 
The major part of the metabolites in both rice leaf and ear was the sulfoxide 
and sulfone. The S-methyl isomer was also found in ears. Using labeled 
material, almost half of the activity was found in bran; 6.54 in the husk, 
and 14.7% in polished rice. Fourteen days after application, water soluble 
metabolites were found in the rice grains: phosphate and thiophosphate, 
dimethyl phosphate and thiophosphate, demethyl fenthion, and an unknown 
compound (452). 
Exposure of fenthion to ultraviolet light gave rise to a compound 
believed to be the sulfoxide (1608). 
After field treatment of coastal bermudagrass and corn with fenthion, 
both were analyzed for residues. The bermudagrass contained residues of 
five metabolites in addition to fenthion: fenthion sulfoxide and sulfone, 
fenthion oxon and its sulfoxide and sulfone. Corn contained residues of 
fenthion, fenthion sulfoxide and sulfone, and fenthion oxon sulfoxide and 
sulfone (1744). 
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