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Pyrethroid isomers (four isomers of permethrin and fenvalerate, eight isomers of cypermethrin, and deltamethrin and its seven isomers) and a racemic mixture of fenpropathrin were examined for degradation rate and route in two Japanese upland soils under the same experimental conditions. Degradation of each pyrethroid isomer was studied at 25C under dark conditions with the 14C-labeled chemicals. The traps isomers of permethrin, cypermethrin and deltamethrin degraded more rapidly than the corresponding cis isomers, and the aS epimers of cypermethrin, fenvalerate and deltamethrin degraded faster than the corresponding chR epimers. The degradation rate of cypermethrin or deltamethrin isomers decreased in order of (trans. aS) > (trans. aR) > (cis, aS) > (cis, c R). The cis Jtrans or aR/aS isomerization hardly occurred in the soils. Based on the minimum and maximum half-lives of individual isomers of each pyrethroid, permethrin was judged to have decomposed most rapidly, followed in decreasing order by cypermethrin, deltamethrin and fenvalerate, with only a slight difference between cypermethrin and deltamethrin. Larger amounts of 14C02 and ester cleavage products were formed in the soils treated with less persistent traps or aS isomers, whereas oxidation products retaining the ester linkage such as diphenyl-ether bondcleavage products and ring-hydroxylated products were of more importance in the soils treated with more stable cis or ceR isomers. A larger amount of bound 14C was formed with cis or caR isomers. Degradation of four isomers of a dichlorovinyl analogue of chrysanthemic acid, the acidic half of permethrin and cypermethrin molecules, was also examined in two soils.

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The metabolic fate of pyriproxyfen [4-phenoxyphenyl (RS)-2-(2-pyridyloxy]propyl ether, Sumilarv) was examined in rats and mice given single oral doses of [pyridyl-2,6-14C]-or \phenoxyphenyl-14C]pyriproxyfen at doses of 2 and 1000 mg/kg. The carbon-14 was excreted almost completely into urine and feces within 7 days after dosing and fecal excretion of carbon-14 predominated in both animals. Excretion of carbon-14 into feces and urine was, respectively, 84-97% and 4-12% of the dose in rats and 64-91% and 9-38% in mice. Major metabolic reactions of pyriproxyfen were (1) hydroxylation at the 4-position of the terminal phenyl ring, (2) hydroxylation at the 2-position of the terminal phenyl ring, (3) hydroxylation at the 5-position of the pyridyl ring, (4) dephenylation, (5) cleavage of ether linkages, and (6) conjugation of the resultant phenols with sulfuric acid or glucuronic acid. Although there was generally no marked difference in the metabolic profile of pyriproxyfen between the two species, significant sex-related differences were found in metabolic reactions 1, 3, and 6 in the rat but not in the mouse.

The photodegradation of fenpropathrin [(RS)‐α‐cyano‐3‐phenoxybenzyl 2,2,3,3‐tetramethylcyclopropanecarboxylate] (I), in water, on soil and on plant foliage, was investigated using 14C‐preparations labelled separately at the cyano group, cyclopropyl‐C1 or in the benzyl ring. On exposure to sunlight, I was photodecomposed with initial half‐lives of >6 weeks in distilled water, 6.0 weeks in humic acid aqueous solution, 2.7 weeks in river water, 1.6 weeks in sea water and 0.5 of a day in 2% aqueous acetone. A triplet photosensitiser, acetone, together with naturally occurring substances in river and sea water, including humic acid, enhanced the photodegradation of I. On three kinds of soil, I was rapidly photodegraded with initial half‐lives of 1–5 days, whereas it was fairly photostable on a mandarin orange leaf. The photoreactions involved were: decarboxylation, hydration of the cyano group to carboxamide, cleavage of the ester or the diphenyl ether linkage, hydrolysis of the carboxamide group to carboxyl, and hydroxylation at either or both of the gem dimethyl groups. The predominant reactions in water were decarboxylation, ester bond cleavage and photo‐induced evolution of [14C] carbon dioxide from the [14C] cyano label; on soil, hydration or ester bond cleavage predominated. The hydration was also of importance in river and sea water. Decarboxylation did not occur on soil and plant foliage.