Reaction mass of 3-phenoxybenzyl (1R,3R)-2,2-dimethyl-3-(2-methylprop-1-en-1-yl)cyclopropanecarboxylate and 3-phenoxybenzyl (1R,3S)-2,2-dimethyl-3-(2-methylprop-1-en-1-yl)cyclopropanecarboxylate (4:1)

Endpoint summary

Description of key information

Hideo Kaneko, et al. investigated the toxicokinetik behavior of phenothrin isomers following dermal exposure (published as Absorption and Metabolism of Dermally Applied Phenothrin in Rats, J. Pesticide Sci. 6, 169 -182 (1981) and summarised their findings as follows:

In dermal treatment of male rats with dust and emulsifiable concentrate (E.C.) of both 14C-[(+)-trans]- and 14C-[(+)-cis]-phenothrin at the rates of 0.2 and 2 mg/rat, the 14C absorption into the body was estimated to be 3 - 7% of the initial dose with dust and 8 - 17% with E.C. The absorption rate of 14C was 4 - 5 times faster with E.C. than with dust, whereas the halt-life of 14C in the blood was 2 - 3 times longer with E.C. than with dust. The radio-carbon absorbed through the skin was almost completely eliminated into urine and feces 6 days after treatment. The 14C tissue residues were very low, except on the treated portion of skin. With single oral administration of both isomers of 14C-phenothrin, roughly 96% of the dose was recovered into the excreta during the following 6 days; a larger amount of 14C was excreted into the feces with the [(+)-cis]-isomer and into the urine with the [(+)-trans]-isomer. Nearly the same metabolites were obtained in oral and dermal treatments with either the [(+)-trans] or the [(+)-cis]-isomer, although the nature and amount of metabolites differed. The major metabolites from the [(+)-trans]-isomer were 3-phenoxy-benzoic acid (free and glycine conjugate) and 3-(4-’-hydroxyphenoxy) benzoic acid (free and sulfate), although small amounts of ester metabolites were also obtained. The cis-isomer afforded larger amounts of ester metabolites which resulted from oxidation at the 4’-position of the alcohol moiety, at the trans and cis methyl of the isobutenyl group, at the trans methyl of the gem-dimethyl group of the acid moiety and at combinations of these oxidations; the amount of the ester-cleaved metabolites was about one-fifth of those from the trans-isomer.

It is likely that in dermal treatment, once entering the blood stream through the skin, the phenothrin isomers are metabolized in a manner similar to oral administration.

Key value for chemical safety assessment

Bioaccumulation potential:

low bioaccumulation potential

Absorption rate - dermal (%):

7