Acaricides and Their Residues in Spanish Commercial Beeswax

Background: The purpose of this work was to determine residues of acaricides in recycled Spanish beeswax.

Results: Chlorfenvinphos, fluvalinate, amitraz, bromopropylate, acrinathrin, flumethrin, coumaphos, chlorpyrifos, chlordimeform, endosulfan and malathion residues were determined by GC-µECD/NPD/MS detection. Owing to the extreme instability of amitraz, this analyte was transformed into the stable end-metabolite 2,4-dimethylaniline, later derivatised with heptafluorobutyric anhydride and determined by GC-µECD/MS. Recoveries from spiked samples ranged from 86 to 108%, while quantification limits varied from 0.10 to 0.30 mg kg(-1) using GC-µECD/NPD, and from 12 to 85 µg kg(-1) by GC-MSD. Of a total of 197 samples analysed, only eight samples (4%) were free of residues of chlorfenvinphos (0.019-10.6 mg kg(-1)), fluvalinate was present in 93.6% of samples analysed (0.027 -88.7 mg kg(-1)), while coumaphos was confirmed in only five of the 134 samples analysed at concentrations of less than 195 µg kg(-1). The remaining acaricides were identified with different levels of incidence at concentrations from 12 to 231 µg kg(-1).

Conclusions: Residues of acaricides were found in an extensive number of beeswax samples. The contamination with chlorfenvinphos and tau-fluvalinate was very relevant, particularly as chlorfenvinphos is not legally authorised for use in beekeeping. The possible impacts of the main acaricides detected on larval and adult honey bees are discussed.