Belgian case study on flumethrin residues in beeswax: Possible impact on honeybee and prediction of the maximum daily intake for consumers

Flumethrin exposure perturbs gut microbiota structure and intestinal metabolism in honeybees (Apis mellifera)

Flumethrin mitigates Varroa's harm to honeybee colonies; however, its residues in colonies threaten the fitness of honeybee hosts and gut microbiota. Our previous research has shown that flumethrin induces significant physiological effects on honeybee larvae; but the effects of flumethrin on the gut microbiota and metabolism of adult honeybees are still unknown. In this study, 1-day-old honeybees were exposed to 0, 0.01, 0.1, and 1 mg/L flumethrin for 14 days and the impacts of flumethrin on the intestinal system were evaluated. The results showed that exposure to 1 mg/L flumethrin significantly reduced honeybee survival and the activities of antioxidative enzymes (superoxide dismutase and catalase) and detoxification enzymes (glutathione S-transferase) in honeybee heads. Moreover, exposure to 0.01, 0.1, and 1 mg/L flumethrin significantly decreased the diversity of the honeybee gut microbiota. Results from untargeted metabolomics showed that long-term exposure to 0.01, 0.1, and 1 mg/L flumethrin caused changes in the metabolic pathways of honeybee gut microbes. Furthermore, increased metabolism of phenylalanine, tyrosine, and tryptophan derivatives was observed in honeybee gut microbes. These findings underscore the importance of careful consideration in using pesticides in apiculture and provide a basis for safeguarding honeybees from pollutants, considering the effects on gut microbes.

The Influence of the Chemical Composition of Beeswax Foundation Sheets on Their Acceptability by the Bee's Colony

Beeswax is one of the most important products for the well-being of bee colonies. The wax glands of young worker bees produce beeswax, which serves as a building material for honeycomb construction. Beekeepers using hives with mobile frames mainly utilize local beeswax to make foundations. Any paraffin addition represents adulteration, resulting in a high degree of contamination. During the preparation of re-used beeswax, losses during the process may instigate producers to add cheaper, wax-like substances like paraffin and tallow. This article presents a systematic investigation of the quality of beeswax foundation from six major producers in Vojvodina, Serbia, by applying the classic analytical procedure for the determination of selected physicochemical parameters and instrumental gas chromatography coupled with mass spectrometry (GC-MS) and Fourier transform infrared attenuated total reflection (FTIR-ATR) spectroscopy techniques. FTIR-ATR detected possible paraffin and beef tallow in 72 foundation sheet samples. This technique was complemented with GC-MS. This analysis revealed that paraffin content ranged between 19.75 and 85.68%, while no tallow was detected over the two-year period. Two sheets from each manufacturer were placed into wired Langstroth-Ruth frames and placed in beehives. The construction, based on built cells, was monitored every 24 h. Evaluating newly inserted sheets proved that without quality nectar, there is no intensive building, regardless of adulteration.

The power to (detect) change: Can honey bee collected pollen be used to monitor pesticide residues in the landscape?

Analysis of trapped honey bee pollen for pesticide residues is the most widely used method of monitoring the amount of pesticide entering colonies and its change over time. In this study, we collected and analyzed pollen from 70 sites across four bee-pollinated crops over two years to characterize the variation in pesticide detection across sites, crops and at different periods during bloom. Hazard Quotient, HQ, is the most common way that pesticide residues are aggregated into a single pesticide hazard value in the current literature. Therefore, change in pesticide hazard (HQ) was quantified in composite pollen samples collected from pollen traps and in pollen color subsamples separated into pollen from the target crop being pollinated and pollen from other plant species. We used our estimates of the variation in HQ to calculate the number of sample location sites needed to detect a 5% annual change in HQ across all crops or within specific crops over a 5-year period. The number of sites required to be sampled varied by crop and year and ranged between 139 and 7194 sites, costing an estimated $129,548 and $3.35 million, respectively. The HQ values detectable for this cost would be 575 and 154. We identified additional factors that complicate the interpretation of the results as a way to evaluate changes in pest management practices at a state level. First, in all but one crop (meadowfoam), the pollen collected from outside the crop honey bee colonies were pollinating comprised a major percentage of the total pollen catch. Moreover, we found that when the overall quantity of pollen from different pollen sources was taken into account, differences in HQ among crops widened. We also found that while HQ estimates remain consistent across the bloom period for some crops, such as cherry, we observed large differences in other crops, notably meadowfoam. Overall, our results suggest the current practice of interpreting pesticides levels in pollen may come with limitations for agencies charged with improving pesticide stewardship due to the high variation associated with HQ values over time and across crops. Despite the limitations of HQ for detecting change in pesticide hazard, there remains a potential for HQ to provide feedback to regulators and scientists on field-realistic pesticide hazard within a landscape.

Effect of fluvalinate on the expression profile of circular RNA in brain tissue of Apis mellifera ligustica workers

Fluvalinate is widely used in apiculture as an acaricide for removing Varroa mites, but there have been growing concerns about the negative effects of fluvalinate on honeybees in recent years. Previous research revealed changes in the miRNA and mRNA expression profiles of Apis mellifera ligustica brain tissues during fluvalinate exposure, as well as key genes and pathways. The role of circRNAs in this process, however, is unknown. The goal of this study was to discover the fluvalinate-induced changes in circular RNA (circRNA) expression profiles of brain tissue of A. mellifera ligustica workers. A total of 10,780 circRNAs were detected in A. mellifera ligustica brain tissue, of which eight were differentially expressed between at least two of the four time periods before and after fluvalinate administration, and six circRNAs were experimentally verified to be structurally correct, and their expression patterns were consistent with transcriptome sequencing results. Furthermore, ceRNA analysis revealed that five differentially expressed circRNAs (DECs) (novel_circ_012139, novel_circ_011690, novel_circ_002628, novel_circ_004765, and novel_circ_010008) were primarily involved in apoptosis-related functions by competitive binding with miRNAs. This study discovered changes in the circRNA expression profile of A. mellifera ligustica brain tissue caused by fluvalinate exposure, and it provides a useful reference for the biological function study of circRNAs in A. mellifera ligustica.

Transfer of xenobiotics from contaminated beeswax into different bee matrices under field conditions and the related exposure probability

Beeswax is known to have a high capacity to accumulate different contaminants due to its fat-soluble properties. Many surveys in Europe and the USA have shown high levels of contamination in beeswax especially with acaricides used for varroa treatment. In this study, we investigated the transfer pathways of various active substances from beeswax into different matrices under field conditions. Honey, bee bread, larvae, and pupae samples were collected 6-8 weeks after building the experimental colonies on different charges of wax foundations. Identification and quantification of the target substances were performed with an established and validated multi-residue method using LC-MS/MS and GC-MS systems. Nine out of 19 active substances in wax could be detected in the analyzed matrices. Our results confirm the migration of different contaminants from wax into different bee matrices including honey, bee bread, and bee brood. The concentration of detected residues in the different matrices was significantly increased by increasing residue concentration in wax. Therefore, the maximum detected residues in the matrices were almost in wax containing high residual concentrations. Bee bread can be considered as the most important matrix due to relatively high detected concentrations and transfer ratios of the most contaminants. A significant effect of the lipophilicity of active substances on the transfer ratio into bee bread was found, which means that increasing the Log P values has positive effects on the transfer ratio. In conclusion, our results provide the first detailed information regarding the migration of active substances from wax into various matrices under realistic field conditions and are fundamentally important for assessing potential exposure and risks for honey bees.

Acaricide flumethrin-induced sublethal risks in honeybees are associated with gut symbiotic bacterium Gilliamella apicola through microbe-host metabolic interactions

Flumethrin is one of the few acaricides that permit the control of Varroa disease or varroosis in bee colonies. However, flumethrin accumulates in hive products. We previously discovered that sublethal doses of flumethrin induce significant physiological stress in honeybees (Apis mellifera L.), however its potential impacts on the honeybee gut microenvironment remains unknown. To fill this gap, honeybees were exposed to a field-relevant concentration of flumethrin (10 μg/L) for 14 d and its potential impacts on gut system were evaluated. The results indicated that flumethrin triggered immune responses in the gut but had limited effects on survival and gut microbial composition. However, survival stress drastically increased in bees exposed to antibiotics, suggesting that the gut microbiota is closely related to flumethrin-induced dysbiosis in the bee gut. Based on a non-targeted metabolomics approach, flumethrin at 10 μg/L considerably altered the composition of intestinal metabolites, and we discovered that this metabolic stress was closely linked with a reduction of gut core bacterial endosymbiont Gilliamella spp. through a combination of microbiological and metabolomics investigations. Finally, an in vitro study showed that while flumethrin does not directly inhibit the growth of Gilliamella apicola isolates, it does have a significant impact on the glycerophospholipid metabolism in bacteria cells, which was also observed in host bees. These findings indicated that even though flumethrin administered at environmental relevant concentrations does not significantly induce death in honeybees, it still alters the metabolism balance between honeybees and the gut symbiotic bacterium, G. apicola. The considerable negative impact of flumethrin on the honeybee gut microenvironment emphasizes the importance of properly monitoring acaricide to avoid potential environmental concerns, and further studies are needed to illustrate the mode of action of bee health-gut microbiota-exogenous pesticides.

The Value of Hazard Quotients in Honey Bee (Apis mellifera) Ecotoxicology: A Review

Estimates of pesticide application hazards have grown to be one of the most common methodologies for evaluating the impact of pest management practices on honey bees. Typically, hazards are estimated by calculating a Hazard Quotient (HQ), which is based on acute toxicity data for different pesticides and the quantity of those pesticides applied to a field or detected on bees and matrices associated with their hive (honey, wax, pollen, and/or bee bread). Although use of HQ is widespread, there have been few reviews of this methodology, particularly with focus on how effective this method is at predicting effects of pesticides on hives. We evaluated 36 relevant papers, containing calculations of HQ to estimate hazards to honey bees. We observed that HQ was primarily calculated using two different approaches: (1) from the concentration of pesticides in the food, hive, or tissues of honey bees or (2) using the field application rate of the active ingredient as the estimation of pesticide hazard. Within and between HQ calculation methods, thresholds vary widely with some HQ thresholds set below 1 and others set at 10,000. Based on our review we identify key weakness with current HQ methodology and how studies relate HQ to honey bee health endpoints. First, HQ thresholds from studies of pesticides in hives are not based on the same pesticide consumption models from the EPA, potentially overestimating the risk of impacts to colonies. Conversely, HQ estimates calculated from field application rates are not based on eco-toxicological estimates of field exposure, resulting in an overestimation of pesticide reaching colonies. We suggest it is for these reasons that there is poor correspondence between HQ and field-level honey bee health endpoints. Considering these challenges, HQ calculations should be used cautiously in future studies and more research should be dedicated to field level exposure models.

Evaluation of pesticide residues in commercial Swiss beeswax collected in 2019 using ultra-high performance liquid chromatographic analysis

The aim of this study was to determine residue levels of pesticides in Swiss commercial beeswax. Foundation samples were collected in 2019 from nine commercial manufacturers for analysis of 21 pesticides using ultra-high performance liquid chromatography. Individual samples showed the variability and residue ranges and pooled samples represented the average annual residue values of the Swiss production. In total, 17 pesticides were identified and 13 pesticides were quantified. They included 13 acaricides and/or insecticides, two fungicides as well as a synergist and a repellent. The means calculated from individual samples were similar to the average annual residue values for most tested pesticides. Mean values of 401, 236, 106 and 3 μg·kg-1 were obtained for the beekeeping-associated contaminants coumaphos, tau-fluvalinate, bromopropylate and N-(2,4-Dimethylphenyl)-formamide (DMF; breakdown product of amitraz), respectively. For the other pesticides, the mean values were 203 μg·kg-1 (synergist piperonyl butoxide), 120 μg·kg-1 (repellent N,N-Diethyl-3-methylbenzamide, DEET), 19 μg·kg-1 (chlorfenvinphos) and 4 μg·kg-1 ((E)-fenpyroximate), while the means for acrinathrin, azoxystrobin, bendiocarb, boscalid, chlorpyrifos, flumethrin, permethrin, propoxur and thiacloprid were below the limit of quantification (< LOQ). Individual samples contained from seven to 14 pesticides. The ranges of values for coumaphos and piperonyl butoxide (from 14 to 4270 μg·kg-1; from 6 to 1555 μg·kg-1, respectively) were larger as compared to the ranges of values for DEET and tau-fluvalinate (from < LOQ to 585 μg·kg-1; from 16 to 572 μg·kg-1, respectively). In conclusion, the most prominent contaminants were the pesticides coumaphos and tau-fluvalinate, which are both acaricides with previous authorization for beekeeping in Switzerland, followed by piperonyl butoxide, a synergist to enhance the effect of insecticides.

The use of the Hazard Quotient approach to assess the potential risk to honeybees (Apis mellifera) posed by pesticide residues detected in bee-relevant matrices is not appropriate

BACKGROUND

Pesticide residue data for pollen and nectar are valuable for characterizing realistic exposure of pollinators, e.g. from agricultural crops, flowering margins. Interpretation of residues relies on comparing exposure with toxicity and the Hazard Quotient (HQ) is widely utilized. However, the HQ (threshold of concern 50) was only validated for foliar sprays, based on application rate as a proxy for exposure, not measured residues in bee-relevant matrices.

RESULTS

A review of the literature showed a range of HQ approaches and thresholds of concern used to assess non-foliar applications and residues detected in bee-relevant matrices, mostly pollen. The use of the HQ thresholds to assess risks associated with residue data or non-foliar spray application methods is not validated, does not reflect realistic exposure and the conclusions reached differ substantially from current risk assessment approaches. Re-evaluation of residue data from the first published use of the concentration-based HQ (2013) and a recent paper (2021) reduced the proportion of pesticides where a conclusion of potential risk was reached from 30 to 7% and 28% to 3-6%, respectively.

CONCLUSIONS

An understanding of the applicability of the selected risk assessment approach to the available residue data is needed to enable robust conclusions to be drawn on the potential risk to bees. Use of the HQ approach to assess the risk posed by application methods other than foliar sprays or residues in nectar and pollen is likely to result in unreliable conclusions. An alternative approach should be used to assess the significance of measured residues.

Non-Occupational Exposure to Pesticides: Experimental Approaches and Analytical Techniques (from 2019)

BACKGROUND

Pesticide residues are a threat to the health of the global population, not only to farmers, applicators, and other pesticide professionals. Humans are exposed through various routes such as food, skin, and inhalation. This study summarizes the different methods to assess and/or estimate human exposure to pesticide residues of the global population.

METHODS

A systematic search was carried out on Scopus and web of science databases of studies on human exposure to pesticide residues since 2019.

RESULTS

The methods to estimate human health risk can be categorized as direct (determining the exposure through specific biomarkers in human matrices) or indirect (determining the levels in the environment and food and estimating the occurrence). The role that analytical techniques play was analyzed. In both cases, the application of generic solvent extraction and solid-phase extraction (SPE) clean-up, followed by liquid or gas chromatography coupled to mass spectrometry, is decisive. Advances within the analytical techniques have played an unquestionable role.

CONCLUSIONS

All these studies have contributed to an important advance in the knowledge of analytical techniques for the detection of pesticide levels and the subsequent assessment of nonoccupational human exposure.

Honey bee exposure scenarios to selected residues through contaminated beeswax

Twenty-two pesticides and veterinary drugs of which residues were detected in beeswax in Europe were selected according to different criteria. The risk to honey bee health posed by the presence of these residues in wax was assessed based on three exposure scenarios. The first one corresponds to the exposure of larvae following their close contact with wax constituting the cells in which they develop. The second one corresponds to the exposure of larvae following consumption of the larval food that was contaminated from contact with contaminated wax. The third one corresponds to the exposure of adult honey bees following wax chewing when building cells and based on a theoretical worst-case scenario (= intake of contaminants from wax). Following these three scenarios, maximum concentrations which should not be exceeded in beeswax in order to protect honey bee health were calculated for each selected substance. Based on these values, provisional action limits were proposed. Beeswax exceeding these limits should not be put on the market.

Pesticide and veterinary drug residues in Belgian beeswax: Occurrence, toxicity, and risk to honey bees

Pesticide and veterinary drug residues are one of the stress factors affecting bee health and mortality. To investigate the occurrence, the concentration and the toxicity risk to bees of pesticide residues in four different types of beeswax (brood comb wax, recycled comb wax, honey comb wax, and cappings wax), 182 samples were collected from apiaries located all over the Belgian territories, during spring 2016 and analysed by LC-MS/MS and GC-MS/MS for the presence of 294 chemical residues. The toxicity risk to bees expressed as the Hazard Quotient (HQ) was calculated for each wax sample, according to two scenarios with different tau-fluvalinate LD₅₀ values. Residues showing the highest prevalence were correlated to bee mortality in a multivariate logistic regression model and a risk-based model was used to predict colony bee mortality. Altogether, 54 different pesticide and veterinary drug residues were found in the four types of beeswax. The residues with a higher likelihood to be retained in beeswax are applied in-hive or with a high lipophilic nature. The multivariate logistic regression model showed a statistically significant influence of chlorfenvinphos on bee mortality. All our results indicated that cappings wax was substantially less contaminated. This national survey on beeswax contamination provides guidelines on the re-use of beeswax by beekeepers and shows the necessity to introduce maximum residue levels for global trade in beeswax. An online tool was developed to enable beekeepers and wax traders to estimate the risk to honey bee health associated with contaminated wax.

Flumethrin at honey-relevant levels induces physiological stresses to honey bee larvae (Apis mellifera L.) in vitro

Varroa mites often inflict heavy losses on the global bee industry and there are few effective control options. Among these methods to control mites, pesticides are extensively used as a cheap, easy to use, and high-efficiency control measure. However, bees are sensitive to many pesticides; thus, a balance between losses induced by drugs and maximum benefits are important for beekeeping and risk assessment. In this study, the effects of flumethrin, a pyrethroid miticide used on bee colonies, was evaluated using bee larvae reared in vitro. We found that flumethrin induced significant mortality during larval metamorphosis and adult emergence. After continuous exposure during the larval stage, significant changes were observed in antioxidative enzymes (SOD and CAT), lipid peroxidation (MDA, LPO, and POD), and detoxification enzymes (GSH, GST, and GR) in the late instar larvae before pupation. It is also noteworthy that flumethrin significantly regulated the expression of immune (Basket and Dscam) and developmental (Amems, Amhex10869, Vtg and Mfe) genes in larvae, which influences can also be found in the subsequent pupae and adult stages. These findings indicate that flumethrin itself is toxic to bee larvae and has potential risks during colony development. Bees are important pollinators and the sustainable and healthy development of colonies is the foundation of pollinating success for agricultural production. This study would provide some useful thinking for pesticides application techniques and processes in risk assessment of pesticides to bee larvae, even colony.

Flumethrin at sublethal concentrations induces stresses in adult honey bees (Apis mellifera L.)

Flumethrin is a typical pyrethroid varroacide widely used for mite control in beekeeping worldwide. Currently, information on the toxicological characteristics of flumethrin on bees at sublethal concentrations is still lacking. To fill this gap in information, we performed a 48-h acute oral and 14-day chronic toxicity testing of flumethrin in newly emerged adult honey bees under laboratory conditions. Results showed that flumethrin had high acute toxicity to honey bees with a 48-h LD₅₀ of 0.47 µg/bee (95% CI, 0.39 ∼ 0.57 µg/bee), which is higher than that of many other commercial pyrethroid insecticides, but lower than that of tau-fluvalinate. After 14 days of chronic exposure to flumethrin at 0.01, 0.10, and 1.0 mg/L, significant antioxidant response, detoxification, immune reaction, and apoptosis were observed in the midguts. These findings indicated that flumethrin had potential risks to bees, and it can disturb the homeostasis of bees at sublethal concentrations under longer exposure conditions. Flumethrin is highly lipophilic and easy to accumulate in beeswax; thus, careless practices might pose risks to colony development in commercial beekeeping and native populations. This laboratory study can serve as an early warning, and further studies are required to understand the real residual level of flumethrin in bees and the risks of flumethrin in field condition.