Under aerobic conditions mesosulfuron was moderately degraded with a half-life of 10 to 150 days. The mineralisation was with varying with around 15 to 30% after 150 days moderate in a few studies. In other studies the mineralisation was poor. Nine metabolites were identified, of which seven accounted for more than 5% of the applied radioactivity. These seven metabolites were considered as major compounds. The six major compounds BCS-AA25052 (AE F092944), O-desmethyl mesosulfuron acid (AE F160460), O-desmethyl mesosulfuron (AE F160459), BCS-AB40283 (AE F099095), mesosulfuron acid (AE F154851) and benzisothiazole (AE F147447) are all moderately slow degraded with a half-life between 10 to 150 days. The only fast degrading major metabolite was Ester sulfonamide (AE F140584), with a half-life shorter than 8 days. The only detected minor metabolite was mesosulfuron-methyl-des-methyl-guanidine (BCS-CV14885).