The aerobic route of degradation of ethametsulfuron methyl was studied in two studies (Pils 2010, subsequently revised as Barefoot 2012, and McCorquodale 2011) in six soils using appropriate radiolabelling positions of the parent substance. It is noted from the aqueous hydrolysis study that rate of hydrolysis is dependent on pH, with faster degradation being exhibited at acid pH than at neutral or alkaline pH (DT50 at 50?C and pH 4, 7 and 9 being 0.4 days, 9.7 days and 14.4 days respectively). With this in mind, it is surprising that the pH range of the soils in which aerobic degradation was studied only spanned a range of pH 6.4 - 7.6 (CaCl2). In the view of the rapporteur, the range should have been wider, in particular encompassing more acidic soils. Omitting soils in which ethametsulfuron methyl may degrade more quickly may disregard the potential that metabolites may have been formed in greater amounts. The Applicant has submitted a case based on degradation seen in the laboratory and in the field. This will be discussed later in the section dealing with the field studies. Ultimately, ethametsulfuron methyl formed moderate levels of unextracted residues at study end (approx. 10-23% AR at 120 DAT) with little difference in the levels between the two radiolabels. Conversely, there were significant differences between the levels of 14CO2 formed, with phenyl labelling position demonstrating CO2 between 24 - 52% AR at 120 DAT, but the triazine labelling position demonstrating only 1 - 12.5% AR as CO2 at 120 DAT. Within the confines of the pH range of the soils used, there appeared to be no trend for any differences in mineralisation or unextracted residues which may be linked to soil pH. [...] The following description is based on the results of the original version of the study and may be unreliable. Three major metabolites were formed which retained the majority of the parent molecule structure, losing only a single methyl or ethyl group. These metabolites were IN-A8768 (5 - 31.5% AR), IN-N7468 (4- 24% AR) and IN-N7469 ( < LOQ 20.1% AR). Generally, occurrence of these three metabolites was IN-A8768, then IN-N7468 and then INN7469. In a single soil there was a suggestion that formation of IN-N7468 and IN-N7469 may be competitive, although the evidence for this is not particularly strong. All three of these metabolites are closely related, but the structures suggest that there is no direct degradation pathway between any of these three metabolites. Two further minor metabolites retaining the majority of the parent molecule structure were also identified in a second study on one single soil. These metabolites were INRXR81 and IN-RYM15. IN-RXR81 had been seen at levels approaching 10% AR in a single soil in the originally conducted route of degradation, but had not been specifically identified, having been named “Unknown A”. The further study confirmed identity, and as it was increasing up to 4% AR at the end of the study confirms to need to include IN-RXR81 in the groundwater assessment. The chromatographic properties of IN-RYM15 suggested that this metabolite had also been found in the original route of degradation study but at levels that would not trigger a groundwater assessment, hence the metabolite had not been specifically identified. The highest level of 5.8% AR at the end of the further study indicates that IN-RYM15 must also be included in the groundwater assessment. Following these relatively small transformations, more extensive degradation occurs the main structure is cleaved at the sulfonylurea bridge giving rise to three metabolites possessing the phenyl ring and four metabolites possessing the triazine ring. However, it is also possible that parent ethametsulfuron undergoes hydrolytic cleavage of the sulfonylurea bridge without any of the relatively minor transformations occurring first. The Applicant argues that a combination of hydrolytic and biological degradation occurs in practice. The phenyl-ring metabolites are IN-D5803 ( < LOQ 8% AR), IN-D5119 (3-12% AR) and IN-00581. IN-00581 was not specifically identified in the initial aerobic route of degradation study, but was identified within the 30 day aerobic phase of the aerobic/anaerobic soil degradation study at up to 4.5% AR and seen as a minor metabolite in the further aerobic route of degradation study. The RMS notes that IN-00581 is a common metabolite of other sulfonylurea herbicides (e.g. metsulfuron methyl and tribenuron methyl), and has the IUPAC name of 1,1-dioxo-1,2-benzothiazol-3-one, commonly called saccharin, a commercially available artificial sweetener. The triazine-ring metabolites are IN-B9161 (14-59% AR), IN-D7556 (8-26% AR), IN-A9795 (2-12% AR) and IN-R7558 (5-10% AR at end of study in a single soil). In total, based on the results of the unreliable Pils 2010/Barefoot 2012 study and reliable McCorquodale 2011 study, 12 metabolites found in these studies are considered to trigger a groundwater assessment according to the criteria in the relevance of metabolites in groundwater guidance document (Sanco/221/2000 rev.10, 25 February 2003). These are: (greater than) 10% AR: IN-D5119, IN-A8768, IN-N7468, IN-B9161, IN-D7556, IN-A9795, IN-N7469; 5-10% AR at two or more consecutive time points: IN-D5803, IN-RXR81, IN-RYM15; Increasing at study end: IN-00581, IN-R7558.