Several metabolites were detected from the laboratory incubation of tefluthrin under aerobic conditions in non-sterile soil and levels of mineralisation were generally high. The maximum measured amount of any single metabolite was 7.1 % of applied radioactivity as Compound Ia. Compound Ia was formed in amounts >5 % at two consecutive timepoints in a single aerobic study. Volatile losses of tefluthrin were a maximum of 15.5 %, equivalent to an average loss by this route of 0.25 % per day at a temperature of 30 °C. Even though volatile losses were not measured in study 1 (Weissler M S and Bewick D W, 1985) recoveries of radioactivity for the granular treatment were never less than 94.8 % suggesting such losses were lower by this mode of application. The pattern of metabolism indicated by these studies is as shown in Figure B.8.1-2 below. Hydrolysis of the ester to the benzyl alcohol (Compound II - not detected) was followed by oxidation to give the benzoic acid, Compound III. Tefluthrin was also oxidised at the methyl group pendant to the phenyl ring giving the carboxylic acid, Compound V. It is not possible to determine whether the only other identified metabolite, the diacid Compound IV, arose from oxidation of Compound III or by hydrolysis and oxidation of Compound V. Compound Ia may be formed by direct hydrolysis either of tefluthrin or Compound V and further oxidises through to CO2. The intended use of tefluthrin as a sugar beet seed treatment involves application in spring on light soils where aerobic metabolism will take place. Under these conditions it is anticipated that degradation will be extensive, major metabolites will not build up and mineralisation will be a significant route of dissipation. Furthermore it is likely that volatile losses will be minimal in line with the findings for the granular application.