The chemistry, metabolism and residue analysis of synthetic pyrethroids

Aerobic metabolism and adsorption of pyrethroid insecticide imiprothrin in soil

“…Although IP was resistant to abiotic hydrolysis under acidic (stable at pH 5) and neutral (half-life of 58.6 days at pH 7) conditions, 17,18) the soil metabolism study exhibited rapid microbial degradation with half-lives of 1.6-2.5 days and 3.3-12.5 days for trans and cis isomers, respectively. Previous studies 8,10) have reported that the aerobic half-lives of synthetic pyrethroids such as phenothrin, permethrin and cypermethrin range from 1 to 14 days with the same isomeric preference. Pyrethroids are known to undergo ester cleavage in the aid of various bacteria isolated from soils, and esterases are considered to participate in the stereoselective reaction.…”

“…The isolated polar metabolite could be confirmed to be PG by two-dimensional TLC co-chromatography. CPG exhibited the maximum formation of 4.6-8.9% at days 3-7 but decreased with PG formation (maximum, 4.1-14.6% at days [7][8][9][10][11][12][13][14]. None of these compounds exceeded 5.3% of the applied 14 C at day 60 and therefore, all of these degradates were considered to be finally stepwise degraded to carbon dioxide or bound to soils.…”

“…8,9) Their main degradation pathways are the hydrolytic cleavage of an ester linkage, stepwise hydration of a cyano group, cleavage of a diphenyl ether bond and ring hydroxylation of a phenoxybenzyl moiety. 10) It has been also reported that geometrical and/or optical isomerism in a pyrethroid molecule can affect metabolic susceptibility; trans isomers are more labile than the corresponding cis isomers.…”

Comparative Toxicology of the Pyrethroid Insecticides

“…Major differences in toxicity to mammals versus insects are attributable to toxicokinetic factors. Valuable reviews have been published on the fate and metabolism of pyrethroids in mammals, including those of Ruzo and Casida (1977), Hutson (1979), Chambers (1980), Miyamoto et al (1981), Leahey (1985), Gray and Soderlund (1985), and NRCC (1986).…”

An overview of sample preparation and extraction of synthetic pyrethroids from water, sediment and soil

“…Although pyrethroids are strongly adsorbed on soil and do not usually leak into groundwater, which reduces short-term bioavailability [11,12], it has been suggested that there is a potential toxicity to sediment-dwelling aquatic organisms, and that live just above the sediment [13]. Variation in composition of commercially available pyrethroids could be one of the reasons for the wide variation in reported toxicities [14]. This comes from the fact that a complex mixture of stereoisomers with very small differences in chemical structure is applied rather than one single pure compound [15].…”