An in vitro model for assessing the toxicity of pesticides in beeswax on honey bee larvae

Pesticide residues in honey: Agricultural landscapes and commercial wax foundation sheets as potential routes of chronic exposure for honey bees

Pesticides pose significant threats to pollinators, and honey bees are frequently exposed through foraging and beekeeping practices. We assessed honey bee pesticide exposure by analyzing 92 pesticide residues in honey from 30 hobbyist apiaries across Massachusetts, along with store-bought honey and commercial wax foundation. For all samples, we calculated the risk of multiresidue toxicity to honey bees and assessed the role of landscape composition in predicting pesticides in local honey. Both honey and wax contained multiple pesticides, particularly neonicotinoids and piperonyl butoxide. Store-bought honey accumulated at least two times more residues than local, but did not differ significantly in toxicity. Overall, honey toxicity levels remained below thresholds of concern for bees and human consumption. Although our study had low agricultural land (∼6 %), croplands were positively correlated with pesticides in honey, while wetlands (∼ 15 %) were negatively correlated. Additionally, our study suggests that commercial wax exacerbates pesticide exposure.

A quantitative Apis mellifera hazard and risk assessment model (AMHRA) illustrated with the insecticide sulfoxaflor: sulfoxaflor environmental science review part VI

In this paper, conceptual models of the exposure pathways outside the hive and the in-hive distribution of pesticide residues brought to the honeybee hive are presented. The conceptual model is based on the natural life history, behavior and diet of individual honeybees (Apis mellifera). Receptor groups of bees with similar diets and potential exposure are defined. From the conceptual model, a quantitative A. mellifera hazard and risk assessment model (AMHRA) is developed and illustrated using sulfoxaflor (SFX) as a case study. The model estimates the exposure of the receptor groups of honeybees within a colony via various routes of exposure. The user selects a deterministic mode to obtain hazard quotients (HQ) or a probabilistic mode to obtain risk quotients (RQ). The model was run in the deterministic mode using the pesticide concentrations in nectar and pollen from a field experiment in which SFX was applied to cotton crops at the highest permitted application rate of 101 g a.i. ha-1. Acute and chronic exposure HQ values were calculated for the adult and larval receptor groups. The results showed that the SFX applied at the highest single application rate following the label directions was not hazardous to honeybees. The probabilistic mode was described but not run.

From larva to adult: In vitro rearing protocol for honey bee (Apis mellifera) drones

Development of a successful in vitro rearing protocol has been essential for pesticide safety assessment of immature honey bee workers under laboratory conditions. In contrast, pesticide safety testing of honey bee drones is limited, in part due to the lack of successful laboratory rearing protocols for this reproductive caste. Considering that healthy drones are essential for successful mating and reproduction of the honey bee queen, a standardized in vitro rearing protocol for honey bee drones is necessary to support reproductive safety studies, as well as to gain a deeper understanding of honey bee drone development. Using the established in vitro rearing protocol for honey bee workers, we modified the days of grafting and pupal transfer, as well as the diet volume, pupation plate orientation, and absorbent tissue in the pupal wells to successfully rear honey bee drones in vitro. In vitro-reared drones were evaluated for gross wing abnormalities, body weight, testes weight, and abdominal area, and compared with age-matched drones reared in field colonies. We found that honey bee drones reared in a vertically oriented pupation plate containing WypAll® absorbent tissue in each well had a mean survival to adulthood of 74 ± 3.5% (SEM) until adulthood. In contrast, drones reared in a horizontally oriented pupation plate containing Kimwipe® absorbent tissue in each well had significantly lower survival (5.5 ± 2.3%) and demonstrated gross wing abnormalities. All in vitro-reared drones had significantly lower body weight, testes weight and abdominal area relative to colony-reared control drones. Accordingly, we successfully developed an in vitro rearing protocol for honey bee drones which has the potential to improve future reproductive safety assessment of pesticides for honey bees.

Analysis of contaminant residues in honey bee hive matrices

Pollinators provide ecological services essential to maintaining our food supply and propagating natural habitats. Populations are in decline due to environmental stressors including pesticides, pathogens, and habitat loss. To better understand the impacts of pesticide exposures on colony health, a field survey in Ohio, USA was conducted to monitor the potential contamination of honey bee colonies by pesticides. Apiaries (n = 10) were situated across an agricultural gradient and samples were collected over a 4-week period encompassing corn planting. Dead bees from entrance traps (DBT), pollen, and in-hive (IH) matrices including bee bread, honey, larvae, and nurse bees were analyzed for a whole suite of pesticides. Out of 210 pesticides targeted, 68 residues were quantified across 306 samples. Neonicotinoids, miticides, and fungicides were the dominant pesticide classes identified throughout all the matrix types. Neonicotinoids were detected at higher concentrations and at higher frequencies compared to fungicides, specifically in field pollen samples. DBT also contained high concentrations of these two contaminant classes, although detection frequencies for neonicotinoids were typically lower. Overall, herbicides and non‑neonicotinoid insecticides were found with low frequency and at low concentrations. For most pesticide classes, trends for the mean concentrations were DBT > IH nurse bees > field pollen > IH larvae > IH honey. Pesticides were detected in 100 % of samples with concentrations ranging from 0.01 ppb (diphenylamine) to 2790 ppb (clothianidin). All samples were contaminated with at least two pesticide residues, while 19 samples presented over ten detects and maximum detections of 20 in DBT. Pesticide residues were positively correlated with agricultural gradients across sites and sampling periods. These findings reveal that foraging leads to the exposure of the entire colony to a wide range of pesticides. Moreover, residues determined in DBT serve as an effective proxy for monitoring hive matrices with significantly less disturbance to active hives.

Temporal entry of pesticides through pollen into the bee hive and their fate in beeswax

Honey bees are often exposed to a variety of contaminants, including pesticides from agricultural use. The aim of this study was to investigate the temporal entry of pesticides into the hive by examining the seasonal timing of honey bees bringing pesticide-contaminated pollen into their colonies and the subsequent accumulation of these pesticides in beeswax. Pollen and beeswax samples were collected biweekly from five colonies situated in an agricultural environment in Switzerland. In pollen, 23 pesticides (out of 50) were quantified, including 4 insecticides, 4 herbicides, 12 fungicides, a transformation product, an acaricide, and a synergist. The maximal insecticide concentration levels measured in individual pollen samples were 69.4 μg/kg (thiacloprid), 48.3 μg/kg (acetamiprid), 13.8 μg/kg (spinosad), and 11.1 μg/kg (indoxacarb), while fungicide levels ranged up to 2212.7 μg/kg (cyprodinil), and herbicides were up to 71.9 μg/kg (prosulfocarb). Eighteen of the pesticides found in pollen were also quantifiable in beeswax. Among these were 17 lipophilic pesticides with logarithmic octanol water coefficients (log Kow) equal or above 2.5, which showed similar temporal profiles and order of accumulation magnitude as in pollen. For example, maximal concentrations measured in individual beeswax samples were 12.4 μg/kg for indoxacarb (insecticide), 986.4 μg/kg for cyprodinil (fungicide), and 21.6 μg/kg for prosulfocarb (herbicide). Furthermore, pesticides with log Kow between 2.5 and 7.0 remained in the beeswax during wax purification. Our study shows that a large variety of pesticides brought into the hive through pollen potentially stay in the beeswax during recycling, thus constantly exposing honey bees to pesticides.

Enhancing knowledge of chemical exposures and fate in honey bee hives: Insights from colony structure and interactions

Honey bees are unintentionally exposed to a wide range of chemicals through various routes in their natural environment, yet research on the cumulative effects of multi-chemical and sublethal exposures on important caste members, including the queen bee and brood, is still in its infancy. The hive's social structure and food-sharing (trophallaxis) practices are important aspects to consider when identifying primary and secondary exposure pathways for residential hive members and possible chemical reservoirs within the colony. Secondary exposures may also occur through chemical transfer (maternal offloading) to the brood and by contact through possible chemical diffusion from wax cells to all hive members. The lack of research on peer-to-peer exposures to contaminants and their metabolites may be in part due to the limitations in sensitive analytical techniques for monitoring chemical fate and dispersion. Combined application of automated honey bee monitoring and modern chemical trace analysis techniques could offer rapid progress in quantifying chemical transfer and accumulation within the hive environment and developing effective mitigation strategies for toxic chemical co-exposures. To enhance the understanding of chemical fate and toxicity within the entire colony, it is crucial to consider both the intricate interactions among hive members and the potential synergistic effects arising from combinations of chemical and their metabolites.

Comparison of APIStrip passive sampling with conventional sample techniques for the control of acaricide residues in honey bee hives

Western honey bees are very sensitive bioindicators for studying environmental conditions, hence frequently included in many investigations. However, it is very common in both research studies and health surveillance programs to sample different components of the colony, including adult bees, brood and their food reserves. These practices are undoubtedly aggressive for the colony as a whole, and may affect its normal functioning and even compromise its viability. APIStrip-based passive sampling allows long-term monitoring of residues without affecting the colony in any way. In this study, we compared the effectiveness in the control of acaricide residues by using passive and conventional sampling, where the residue levels of the acaricides coumaphos, tau-fluvalinate and amitraz were evaluated. Conventional and APIStrip-based sampling differ in methods for evaluating bee exposure to residues. APIStrip is less invasive than conventional sampling, offers more efficient measurement of environmental contaminants, and can be stored at room temperature, saving costs and minimizing operator error.

Heavy Metal Concentrations of Beeswax (Apis mellifera L.) at Different Ages

Beeswax is a naturally occurring product that worker bees produce. Beeswax is used in a variety of industries and pharmaceuticals. Humans utilize it extensively in cosmetics, medicinal formulations, and food manufacturing. Beeswax is an essential component of advanced contemporary beekeeping. Beekeepers, in particular, utilize significant amounts of beeswax to make beeswax comb foundation. In its natural condition, beeswax is white, but it becomes yellow then dark in color when it comes into touch with honey and pollen. The ongoing use of wax comb in bee activities (such as brood rearing, storage honey and bee bread), combined with environmental factors such as heavy metal and pesticide residues, resulted in a black color. Because of heavy metals can accumulate in wax for decades, beeswax can be a helpful tool for gathering data on hazardous contaminants in the environment. Because of their lipid-based chemical composition, beeswax combs act as a sink for numerous ambient pollutants as well as poisons when in the hive. The current study aims to measure nine heavy metals and important elements, including iron (Fe), chromium (Cr), zinc (Zn), copper (Cu), nickel (Ni), manganese (Mn), lead (Pb), cadmium (Cd), and cobalt (Co) in beeswax collected in the Behaira governorate region of Egypt between 2018 and 2022. Sample collection was conducted each year in triplicate. The samples were analyzed using an atomic absorption spectrophotometer. The quantity of metals in beeswax at different ages differed significantly. Depending on the wax age, Fe has the highest concentration in the range of 2.068 to 5.041 ppm, while Cd has the lowest ratio at 0.024 to 0.054 ppm from the first to fifth years old of comb age. The findings showed that as beeswax combs aged, the concentration of heavy metals rose. According to the study, it should gradually recycle beeswax combs each year and also adding new foundations.

Pesticide residues in bee bread, propolis, beeswax and royal jelly - A review of the literature and dietary risk assessment

Due to pollinator decline observed worldwide, many studies have been conducted on the pesticide residue content of apicultural products including bee bread, propolis, beeswax and royal jelly. These products are consumed for their nutraceutical properties, although, little information is available on the human health risk posed by pesticides present in them. In our research, studies dealing with the pesticide contamination of the above-mentioned hive products are reviewed. Dietary exposures were calculated based on the recommended daily intake values and concentration data reported by scientific studies. Potential acute and chronic health risk of consumers were evaluated by comparing the exposure values with health-based guidance values. Available data indicate that a wide range of pesticide residues, especially acaricides may accumulate in bee bread, propolis and beeswax, up to concentration levels of more thousand μg/kg. Based on our observations, tau-fluvalinate, coumaphos, chlorfenvinphos, chlorpyrifos and amitraz are commonly detected pesticide active substances in beehive products. Our estimates suggest that coumaphos and chlorfenvinphos can accumulate in beeswax to an extent that pose a potential health risk to the consumers of comb honey. However, it appears that pesticide residues do not transfer to royal jelly, presumably due to the filtering activity of nurse bees during secretion.

Coumaphos residue transfer to honey bee brood (Apis mellifera) in realistic scenarios

Coumaphos is a veterinary treatment administered for the control of Varroa destructor in honey bee colonies. The detection of its residues, however, has been frequently reported in beeswax. This study is pioneer to investigate whether the honey bee brood is exposed to coumaphos via contact or by ingestion of food resources due to a residue transfer inside the bee hive. This field study addresses two scenarios: 1) after its administration according to the posology using strips inside the bee hives and, 2) placing contaminated wax containing coumaphos at 10 mg/Kg into the bee hives (simulating the use of recycled wax). In bee bread, the average concentrations of residues (mean ± s.d.) were 246.66 ± 772.29 ng/g and 192.55 ± 320.19 ng/g in scenario 1 and 2, respectively. In honey, residue concentration was 1.98 ± 5.41 ng/g and 1.93 ± 6.59 ng/g. In scenario 2, exposure has led to residue detection in all larval stages at concentrations ranging from 51.93 to 383.42 ng/g (larvae), 42.20-58.54 ng/g (prepupae), 18.35-26.24 ng/g (pupae) to 21.92-35.92 ng/g (born bee). This study shows that there is a high risk for the bee brood (larvae) by ingestion of bee bread when the residue concentration is >251.31 ng/g. Residue levels in larvae or in prepupae >42.20 ng/g give rise to a moderate risk.

Acaricide residues in beeswax. Implications in honey, brood and honeybee

For beekeeping to be sustainable, the management of colonies for the production of bee products must be economically viable without endangering the lives of bees, and must include acceptable practices such as the treatment of hives with appropriate products. Occasionally, the use of acaricides to treat the hives against varroosis is uncontrolled and can accumulate in the hives, putting the colonies at risk. In this work, a screening of seven acaricides was carried out in different apiaries in Andalusia (Spain). Their distribution in beeswax, brood, honey, and bees from colonies in different surroundings was evaluated at different times. It was found that beeswax was highly contaminated but honey, brood and bees had acceptable levels, below their respective MRL or LD50, after a certain period following varrocide treatments. Acaricides banned for their use against Varroa, such as chlorfenvinphos, cypermethrin and especially acrinathrin, were found in the hives analysed.

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.

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.