Natural occurrence of semicarbazide in heather honey

Regulatory bodies aim to protect consumers from harmful substances. The use of certain antibiotics is prohibited in food-producing animals in the EU due to their potential detrimental effects on humans. Among these are nitrofuran antibiotics, which degrade rapidly so that their metabolites are used as markers in screening for their illegal use. The use of one metabolite, semicarbazide (SEM), as a marker for detecting the antibiotic nitrofurazone, has been criticized due to the many pathways it can be formed by and its natural occurrence in some food items. A recent change in the reference point of action (RPA) for SEM, as stated in Commission Regulation (EU) 2019/1871, due to a reassessment of sensitivity of the analyses, poses a problem for the export of heather honey in Norway. Norwegian heather honey seems to exceed the lowered RPA in numerous cases. Here we show that Norwegian heather honey samples, but not polyfloral 'summer' honey samples from the same hives, contain SEM. The simplest explanation for the demonstrated pattern is a natural source of SEM in heather honey, not the use of a banned antibiotic. Based on our results, we propose that an exception to the EU regulation should be added, exempting heather honey derived from Calluna vulgaris unless other nitrofurans or their metabolites are found together with SEM.