Contamination of honey by the herbicide asulam and its antibacterial active metabolite sulfanilamide

Abstract

A number of antibacterial drugs (antibiotics) like sulfonamides, tetracyclines and streptomycin are used for the treatment of bacterial diseases in beehives. Yet, the finding of sulfanilamide residues in some 15 Swiss honeys out of some 350 samples could not be explained by such apicultural practice. Bees occasionally collect nectar from meadows treated with the herbicide asulam. Such honey is not only contaminated by asulam, but also by its degradation product sulfanilamide. This is the first report that the use of a herbicide causes the appearance of residues of an antibacterial active metabolite belonging to the category of sulfonamide drugs in food. The relevance of this finding lies in the fact that the use of the herbicide asulam might cause unacceptable residue levels of sulfanilamide in a product for human consumption.

Keywords:

• sulfonamides
• sulfanilamide
• asulam
• honey
• metabolite
• liquid chromatography-mass spectrometry (LC/MS)

Acknowledgement

The comprehensive investigations of Matthias Mueller, Official Center of Crop Protection of the Canton Aargau, concerning the agricultural use of asulam are greatly appreciated. The authors gratefully acknowledge the helpfulness, courtesy and patience of the affected beekeepers during the time-consuming investigations.