Analysis of contaminants and residues in beeswax samples after flooding: an exploratory study

Extreme flooding events can lead to the spread or remobilisation of contaminants and residues from historical accumulations in sediments and from substances deposited in industrial agricultural and high-traffic areas. Beeswax that is exposed to floodwater may, over time, accumulate some of these substances, both because of its affinity for lipophilic substances and because of its ability to bind trace elements (TE) that are either dissolved or bound to particles. The aim of this exploratory study was to analyse beeswax with regard to general composition (dry matter, crude protein, ether extract, crude ash), TE, polycyclic aromatic hydrocarbons (PAHs) as well as pesticide and pharmaceutical residues after a flooding event. A total of 14 beeswax samples were analysed, including six samples from flood-affected locations. Eight samples from nearby locations not exposed to floodwater were used as control group. Flooded samples showed increased crude ash contents compared to the control samples, indicating an input of material into the wax during the flooding event. Median concentrations for several TE were elevated compared to the control, including Pb (median: 988 vs 87 ppb; p = 0.008), Zn (6715 vs. 514 ppb; p = 0.001) and Hg (4 vs. 1 ppb; p = 0.008). PAHs concentrations were elevated in the flood-affected samples. The median total concentration of all 16 PAHs analysed was 115 µg/kg in the flood-affected samples, compared to 16 µg/kg in the control samples. Differences were found between the sample groups for several substances (Mann–Whitney U test, p < 0.05). Pesticide residues occurred in both groups with high variability, but seemed to be independent of any flood-related trends. The results suggest that this specific flooding event contributed to the remobilisation of contaminants and residues, which were reflected in the beeswax. This might indicate possible safety issues for bee health or honey production, if flooded beeswax is reused in wax cycles.