14CO2 was a major metabolism product in all soils in both the cyclopropyl- and phenoxy-label test systems. In addition to mineralisation, a large proportion of the applied radioactivity was associated with the soil organic matter. Dissipation of lambda-cyhalothrin in all soils was rapid, with the parent compound representing an average of 28.3% (18 Acres), 16.0% (Nebraska), 1.6% (Gartenacker) and 9.7% (Marsillargues) of the applied radioactivity after 120 days. Cleavage of the parent ester was a predominant route of degradation yielding the carboxylic acid compound Ia and compound V, which were ultimately mineralised to carbon dioxide. Compound XV, formed by hydroxylation of the parent compound, was the only metabolite which exceeded 5% AR (7.7 and 5.8% AR after 14 and 30 days, respectively). Unknown C from the cyclopropyl label was shown to be the same as unknown B from the phenoxy label, by overlapping TLC analysis of extracts from both labels and it was therefore referred to as unknown Z. Efforts (LC-MS and GC-MS of isolated compound Z, and LC-MS analysis against reference standard R175664) failed to identify this metabolite. Unknown Z was observed as max 5.1% AR (mean, day 30, 18 Acres), and in all soils the amounts of unknown Z decreased towards the end of incubation. For compound Ia, no kinetic evaluation was provided in the study because the measured levels were too low to obtain acceptable kinetic fits. Some hydrolytic conversion of the cis-B-diastereoisomer lambda-cyhalotrin to the cis-A diastereoisomer was observed in neutral and alkaline soils. The conversion occurred to a large degree immediately after application. Summarizing the results of the normal phase HPLC analysis, the applicant showed that the most prevalent shift was observed in the alkaline Marsillargues soil (pH 7.8), in which the cis-A pair accounted for 31% total cis-cyhalothrin at the start of the incubation and increased to 37% at 30 days after application. In the neutral Gartenacker soil (pH 7.2), an immediate minor shift to the cis-A pair (6% total cyhalothrin) was observed which was still observable with 4% 30 days after application. During incubation, a shift in the ratio of the cis-B enantiomers from a 1:1 ratio towards about 28 - 35% 1R,cis,ZS’- enantiomer (􀈖-cyhalothrin) at approximately DT75 was observed; the authors attributed this shift to preferential metabolism.