Comparison of transfer of different sulphonamides from contaminated beeswax to honey.

Introduction: No maximum residue limits in honey have been legislated in the EU for antimicrobial substances such as sulphonamides, and they are not permitted, therefore, for treating honey bees unless in a cascade system. Since sulphonamides are used illegally in apiculture to treat foulbrood, their residues can be found in honey and other apiculture products, including beeswax. The study aimed to assess the contamination of honey from beeswax containing residues of 10 sulphonamides (sulphadimethoxine (SDM), sulphadoxine (SDX), sulphamonomethoxine (SMM), sulphamethoxazole (SMX), sulphameter (SMT), sulphamethazine (SMZ), sulphamerazine (SMR), sulphadiazine (SDA), sulphathiazole (STZ) and sulphacetamide (SCA)).

Material and methods: Wax-based foundations fortified with 10 sulphonamides at 10,000 μg/kg were evaluated for sulphonamide concentrations and then placed in a beehive so that honey bees (Apis mellifera L.) could build honeycombs with them. Frames of capped honey were taken out of the hives one month later and honey was sampled from them. The honeycombs were subsequently incubated in a laboratory at 35°C for five months, and honey was sampled monthly. The honey sulphonamide concentrations were measured using liquid chromatography-tandem mass spectrometry and compared to the wax-based foundation concentrations.

Results: The maximum transfers to honey of the initial amount of SDM, SDX, SMM, SMX, SMT, SMZ, SMR, SDA, STZ and SCA in the wax-based foundations were 42.6, 34.3, 31.7, 30.1, 29.5, 25.2, 18.7, 16.1, 9.5 and 8.6%, respectively.

Conclusion: This study demonstrated that every tested sulphonamide could migrate from beeswax in antimicrobial-tainted honeycombs to honey, SDM having the highest migration potential and SCA the lowest.