Flumethrin residue levels in honey from apiaries of China by high-performance liquid chromatography

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.

Human exposure to endocrine-disrupting organochlorine and organophosphate pesticides in locally produced and imported honey in Nigeria

The practice of exposing honeybees to pesticides by bee-keepers or via agricultural crops, is one of the ways in which honey becomes contaminated with pesticides. Though honey has many health advantages, however, human exposure to pesticides via consumption of honey has generated public health concerns due to their endocrine-disruptive abilities. Thus, this study evaluated human exposure to endocrine-disrupting pesticides in honey from Nigeria to establish the safety of honey consumed in Nigeria. Honey were analyzed for pesticides using a gas chromatograph combined with an electron capture detector. The concentrations of ∑20 OCPs and ∑14 OPPs in the honey ranged from 0.45-1045 ng/g and 1.13-632 ng/g respectively. The values of both individual and cumulative non-carcinogenic and carcinogenic risks for humans were <1 and 1 × 10-4 respectively suggesting that there are no potential health risks via the honey consumption. The source analysis showed that pesticides in these honey originated from historical and recent/fresh use.

Early larval exposure to flumethrin induces long-term impacts on survival and memory behaviors of adult worker bees Apis mellifera

Flumethrin has been supplied as an acaricide for Varroa mite control in world-wide apiculture due to its low lethal effects on honey bees. However, little is known about the effects of short-term flumethrin exposure in the larval stage on adult life stage of bees involving survival status, foraging and memory-related behaviors. Here, we found that exposure to flumethrin at 1 mg/L during larval stage reduced survival and altered foraging activities including induced precocious foraging activity, decreased foraging trips and time, and altered rotating day-off status of adult worker bees using the radio frequency identification system. Furthermore, larval exposure at 1 mg/L flumethrin influenced the correct proboscis extension responses of 7-day-old worker bees and decreased homing rates of 20-day-old worker bees, suggesting that 1 mg/L flumethrin exposure at larval stage could affect memory-related behaviors of adult bees; meanwhile, three genes related to memory (GluRA, Nmdar1 and Tyr1) were certainly down-regulated varying different flumethrin concentrations (0.01, 0.1, and 1 mg/L). Combined with transcriptomic sequencing, differentially expressed genes involved in olfactory memory of adult bees were completely down-regulated under flumethrin exposure. Our findings highlight the unprecedented impact of short-term exposure of insecticides on honey bees in long-term health monitoring under field conditions.

The adverse impact on lifespan, immunity, and forage behavior of worker bees (Apis mellifera Linnaeus 1758) after exposure to flumethrin

Several pyrethroids (such as flumethrin and fluvalinate) with low toxicity to honey bees and comparable high toxicity to mites are used worldwide as acaricides. However, flumethrin has been used for a long time in colonies to control Varroa destructor and the honey bees might be exposed to flumethrin cumulatively, which could affect the health of honey bee colonies. This study evaluated the potential adverse effects of direct flumethrin exposure on worker bees under laboratory and colony conditions. Under laboratory conditions, downregulation of genes related to immune was observed when worker bees were exposed to flumethrin above 1/16 LD₅₀; at levels above 1/8 LD₅₀, olfactory learning was impaired, and genes related to learning memory were downregulated; and at >1/4 LD₅₀, their lifespan was shortened. Monitoring with radio frequency identification (RFID) revealed that worker bees in a colony exposed to flumethrin above 1/8 LD₅₀ had a shortened lifespan and reduced foraging ability. When worker bees are exposed to >1/4 LD₅₀ of flumethrin, it can lead to excessive rest day behavior. These results indicate that applying flumethrin in colonies may pose a severe health risk to honey bees and reveal the urgent need to develop non-toxic and highly effective acaricides.

Effects of larval exposure to the insecticide flumethrin on the development of honeybee (Apis mellifera) workers

Flumethrin is a widely used acaricide, but its improper use often leads to residue accumulation in honeybee colonies, thus threatening the health of honeybees, especially at the larval stage. Therefore, this study aimed to describe the direct toxicity of flumethrin on honeybee (Apis mellifera) larvae by conducting bioassays for immune and detoxification-related enzymes and transcriptome sequencing to determine the potential effects on newly emerged adults who were exposed to flumethrin during the larval stage. Results showed that the higher the concentration of flumethrin the honeybee larvae were exposed to, the greater the damage to the physiology of honeybee larvae and the newly emerged worker bees. When honeybee larvae were exposed to flumethrin concentrations higher than 0.01 mg/L, the activities of glutathione sulfur transferase and carboxylesterase were affected, and the metabolism-related genes in the head of newly emerged honeybees exposed to flumethrin during the larval stage were down-regulated. Flumethrin concentration higher than 0.1 mg/L significantly increased mixed-functional oxidase content in honeybee larvae, reduced the larval survival rate, and down-regulated the expression levels of olfactory-related and antioxidant-related genes in newly emerged honeybees. Furthermore, a flumethrin concentration of 1 mg/L significantly down-regulated the expression levels of immune and detoxification-related genes in newly emerged honeybees. These findings provide a comprehensive understanding of the response of honeybee larvae to sublethal flumethrin toxicity and could be used to further investigate the complex molecular mechanisms in honeybees under pesticide stress.

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 negative effect of flumethrin stress on honey bee (Apis mellifera) worker from larvae to adults

Flumethrin is a highly effective acaricide, but its lipophilic characteristic has some negative effects, such as accumulation in bee hives and bee products. However, studies on the survival stress of honey bees subsequent to chronic flumethrin exposure are limited. To answer this question, a study was carried out on the stress to honey bee (Apis mellifera) workers from larvae to adults by chronic exposure to sublethal concentrations of flumethrin. Three flumethrin treatment groups (1, 0.1, 0.01 mg/L) and one control group (with no added flumethrin) were established and divided the worker larvae into four groups. Then, starting with 2-day-old larvae, larvae and subsequent emerged worker bees of the four groups were orally fed with the corresponding concentrations of flumethrin until all the adult worker bees died, respectively. When the concentration was at 0.01 mg/L of flumethrin, the lifespan of adult worker bees decreased, and a down-regulation of detoxification-related genes (CYP450,GSTS) was induced in 1-day-old pupae. When it is at 0.1 mg/L flumethrin, the lifespan of adult worker bees was again shortened, and down-regulation of memory-related genes (GluRA1, Nmdar1, Tyr1) in 1-day-old pupae and gene Tyr1 in 1-day-old worker bees, detoxification-related genes (CYP450,GSTS) in 1-day-old pupae, and immunity genes (Defensin1, Hymenoptaecin) in 7-day-old worker bees were observed. When the concentration is at 1 mg/L flumethrin, lighter birth weight of newly emerged honeybee was found and deficiencies in olfactory learning and memory were observed in 7-day-old worker bees. Memory-related genes (GluRA1, Nmdar1, Tyr1) were down-regulated in 1-day-old pupae and genes (Nmdar1,Tyr1)in 1-day-old worker bees, as were detoxification-related genes (CYP450,GSTS) in 1-day-old pupae and gene CPY450 in 7-day-old worker bees, and immune genes (Defensin1, Hymenoptaecin) in 7-day-old worker bees. There was no significant difference in pupal weight, capping rate, emergence rate, expression of immune-related genes of 1-day-old pupae, expression of immune-related genes and detoxification-related genes of 1-day-old worker bees, expression of memory-related genes and detoxification-related gene GSTS of 7-day-old worker bees. These data provide an ominous warning about the unintended consequences on apiaries, and underscore the need for careful control of flumethrin residues in bee hives.

Honey bee Apis mellifera larvae gut microbial and immune, detoxication responses towards flumethrin stress

Mites are considered the worst enemy of honey bees, resulting in economic losses in agricultural production. In apiculture, flumethrin is frequently used to control mites. It causes residues of flumethrin in colonies which may threaten honey bees, especially for larvae. Still, the impact of flumethrin-induced dysbiosis on honey bees larval health has not been fully elucidated, and any impact of microbiota for decomposing flumethrin in honey bees is also poorly understood. In this study, 2-day-old larvae were fed with different flumethrin-sucrose solutions (0, 0.5, 5, 50 mg/kg) and the dose increased daily (1.5, 2, 2.5 and 3 μL) until capped, thereafter the expression level of two immune genes (hymenoptaecin, defensin1) and two detoxication-related genes (GST, catalase) were measured. Meanwhile, the effect of flumethrin on honey bee larvae (Apis mellifera) gut microbes was also explored via 16S rRNA Illumina deep sequencing. We found that flumethrin at 5 mg/kg triggered the over expression of immune-related genes in larvae, while the larval detoxification-related genes were up-regulated when the concentrations reached 50 mg/kg. Moreover, the abundance and diversity of microbes in flumethrin-treated groups (over 0.5 mg/kg) were significantly lower than control group, but it increased with flumethrin concentrations among the flumethrin-treated groups. Our results revealed that microbes served as a barrier in the honey bee gut and were able to protect honey bee larvae to a certain extent, and reduce the stress of flumethrin on honey bee larvae. In addition, as the concentration of flumethrin increases, honey bee larvae activate their immune system then detoxification system to defend against the potential threat of flumethrin. This is the first report on the impact of flumethrin on gut microbiota in honey bees larvae. The findings revealed new fundamental insights regarding immune and detoxification of host-associated microbiota.

In vitro toxicological assessment of flumethrin's effects on MCF-7 breast cancer cells

Pyrethroid pesticides are frequently used for household insect control of insects and in agriculture and livestock. Flumethrin is a pyrethroid that is used against ectoparasites in many animals. The goal of this study was to evaluate the cytotoxic, apoptotic, genotoxic, and estrogenic effects of flumethrin on the mammalian breast cancer cell line (MCF-7). Compared with control groups, a dose-dependent decrease was observed in cell viability at concentrations of 100 µM and higher. The cytotoxic and apoptotic effects detected by LDH assay and AO/EtBr staining increased significantly at a concentration of 1000 µM. The expression of BCL2, which is an anti-apoptotic gene, significantly decreased, whereas BAX, TP53, and P21 expression significantly increased. The results of a comet assay indicated that flumethrin significantly changed tail length, tail % DNA, tail moment, and Olive tail moment in concentrations above 1 and 10 µM. In addition, a 0.1 µM concentration of flumethrin affected ERα receptor mediated cell proliferation and increased transcription of estrogen-responsive pS2 (TFF1) and progesterone receptor (PGR) genes. As a result, flumethrin-induced apoptosis and cytotoxicity at a high concentration, while induced genotoxicity even at lower concentrations. Flumethrin is an endocrine disrupting insecticide with estrogenic effects at very low concentrations.

Pesticide residues in honey and their potential reproductive toxicity

Honey is the sweet natural substance produced by honeybees. It may be contaminated with pesticide residues due to its intensive use. Almost no reviews have addressed pesticide residues in honey, calculated a hazard index or discussed their potential reproductive toxicity. The focus of this article is primarily to summarize advances in research related to pesticide residues, estimate daily intake of pesticide residues from consuming honey only and discuss the potential reproductive toxicity associated with those residues. The results showed that 92 pesticide residues were found in honey samples from 27 countries. Six residues belong to class IA toxicity, eight residues belong to class IB toxicity, 42 residues belong to class II, 35 residues belong to class III and one residue belong to class IV toxicity. The calculated hazard indices (HIs) suggest high potential health risk by consuming honey. In addition, residues found in honey are known to impair semen quality among exposed individuals and experimental animal models. In conclusion, consumption of honey as one of many food items contaminated with pesticide residues may induce male and female reproductive toxicity in consumers.

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.