Since several years the Swiss cantonal laboratories carry out regularly control of antibiotic residues in honey. In few honeys residues of an unknown sulfonamide, sulphanilamide, have been detected. We investigated in one particular case, in order to find out the contamination source. The honeys concerned were harvested in three apiaries situated in an area of 1 km2 with four agricultural units. At the end of April 2001 and 2002, during the dandelion blooming period, a surface treatment with the herbicide asulam was carried out against the broad leaved Dock (Rumex obtusifolius). In 5 out of 6 spring honeys which were harvested thereafter in the 3 apiaries residues of asulam and sulphanilamide were found: the higher the asulam values, the higher the sulphanilamide residues. Sulfanilamide is a break-down product of asulam. The contamination, expressed in mg/kg was: sulphanilamide average 244, minimum 13, maximum 702; asulam average 84, minimum 10, maximum 230. The Swiss tolerance limit, expressed in mg/kg, is : asulam : 200, sulfanilamide, 50. Due to these results the Swiss Federal Agricultural Office has decided to take measures for banning the application of asulam on whole blooming pastures.
Contamination of honey by a sulfonamide after the use of a herbicide in agriculture