The Smaller the Plastic, the Larger the Impact
Bees are exposed to microplastics when foraging on contaminated nectar, pollen, water and plant resins. A “microplastic” is defined as a polymer particle with a plasticizer component (a substance that makes it “plastic” and flexible). Microplastics are particles less than 5 mm in size that are formed through biological, physical and/or chemical weathering processes. Microplastics smaller than 1 micrometer (“1 μm”) are termed “nanoplastics” and research is showing that these smaller particles pose greater ecological & health risks.
Studies on honey bee microplastic exposure started in 2020, and are largely done under laboratory conditions. Like pesticides, microplastics present dose-dependent “sublethal effects”- health impairments that occur at low-level exposure to microplastics. These effects will be examined here, along with their implications on the honey produced from microplastic-burdened hives. Short answer: You shouldn’t worry about microplastics in honey for human consumption.
Studies on the Health Impacts of Plastics on Honey Bees
A definition: sublethal effects occur when an organism is exposed to low-levels of a contaminant, resulting in impairments to its physiology, behaviour and/or reproduction (as opposed to killing it outright), the “sub” means “below” lethal levels.
Microplastics Impair Sucrose Response, Learning & Memory
Pasquini & colleagues found that when plexiglass nanospheres (“small particles”) were given to bees, there were no effects on sucrose responsiveness in the treatment groups (50, 5 and 0.5 mg/L of microplastics; Pasquini et al., 2024). When this was repeated with polystyrene nanospheres, the bees showed a decreased sucrose response compared to the control group. As with pesticides, a combination of the two microplastics produced worse health outcomes for the bees, impairing their ability to detect sucrose at both high & low sugar concentrations (50 & 5 mg/L respectively).
A proboscis extension response test showed that both polystyrene and plexiglass impaired the bees’ learning and memory, with combined exposure having a greater impact (Pasquini et al., 2024). Further, the bees in the treatment groups were less likely to associate the smell of a stimulant (1-nonanal or 1-hexanol, alcohols with distinct odours) with the presence of a sucrose reward. Any responsive bees were reassessed for medium-term & early-long-term memories capabilities after 2- & 24-hours respectively, to determine if they were able to form memories that associated the odour with a sugary reward.
“But Mister HolyHabibee Entomologically, how did these microplastics enter the bees’ brain?”. We do not know exactly, and several hypotheses have been proposed that are beyond the scope of this article: receptor-mediated endocytosis, paracellular leak after tight-junction damage, protein-corona–mediated interactions and the plain simple from-gut-to-brain route. See Ma et al., 2025 for the latest research on this topic, or Prüst et al., 2020 for an open-access review.
Implications for the Beekeeper: Anticipate Decreased Pollination
Impaired learning & memory hinders foraging, as the worker may be unable to recall profitable foraging sources to her nestmates; perhaps it also diminishes her ability to correctly learn & perform waggle dances. The implications of a reduced sucrose response makes bees reject an otherwise-normal source of nectar, as its sugar hit does not stimulate them to continue foraging from that plant, leading to two outcomes:
- That plant is now less likely to get pollinated and set seeds/fruit. Not ideal if it’s your backyard veggie patch, or if you’re commercially-pollinating a relatively-low nectar producing plant (e.g. almonds)
- The forager will not advertise the plant’s location to her nestmates (“waggle dance”), and so the colony are led away from a potential food source
- This is not so bad, as bees are generalists and will find another plant with more- sugary nectar. It could even be a net benefit for non-A. mellifera pollinators
- If the sucrose unresponsiveness is extreme (as in reduced sensitivity to the high concentrations tested above), then the colony would become stressed as the foragers do not detect suitable food sources nearby. The starvation compounds with other stressors (Varroa, temperature fluctuations) and could cause colony collapse, or premature robbing other hives’ honey stores in an apiary
- Such a scenario is unlikely… unless your hives are located to the outlet valve of a third-world plastic incinerator
- If the sucrose unresponsiveness is extreme (as in reduced sensitivity to the high concentrations tested above), then the colony would become stressed as the foragers do not detect suitable food sources nearby. The starvation compounds with other stressors (Varroa, temperature fluctuations) and could cause colony collapse, or premature robbing other hives’ honey stores in an apiary
- This is not so bad, as bees are generalists and will find another plant with more- sugary nectar. It could even be a net benefit for non-A. mellifera pollinators
What can you do? Perhaps keep strong hives with a double brood box to reduce the disease (contamination?) burden on colonies; eventually the microplastic loads will pass, and strong hives with large populations survive.
Nanoplastics Impair Pollen Metabolism & Gut Microbiota
Wang and colleagues examined how microplastic particle size impacted honey bee health and found that size matters: the smaller the particle size (nanoplastics), the greater its effects (Wang et al., 2022). Bees in the 100 nm polystyrene group had thinner intestinal walls and deeper crypts (a sign of intestinal distress). This was compounded by the nanoplastics’ attachment to the pollen grain’s cell walls and germination pores, which reduced the gut’s ability to digest the pollens.
By contrast, the larger microplastics did not impair pollen metabolism or bee development, instead harbouring microorganisms1 (sick of all these micro- terms yet?) on their larger surface area. The microplastic particles did not have a visible effect on the gut’s microbiota, whereas their nanoplastic counterparts did. Two dominant bee gut microbes, Bifidobacterium & Lactobacillus, had their populations reduced after exposure to 100 nm polystyrene, and the authors suggest that this was due to impaired pollen digestion, as mentioned above (Wang et al., 2022).
Nanoplastic-exposed bees were more susceptible to infection by Hafnia alvei, an opportunistic pathogen (i.e. it only causes gut problems when said gut has problems; Wang et al., 2022). Combined with the thinner intestinal wall, other pathogenic bacteria may escape the gut and enter the haemolymph. In mammals this leads to sepsis requiring antibiotics. In bees? It also causes sepsis, leading to individual bee mortality. Imbalances in gut microbiota cause multiple downstream effects: increased vulnerability to agrichemicals, immune system dysregulation, impaired development and the bee-equivalent of “abnormal” psychology, amongst others.
The peritrophic membrane is a gut lining in insects, that acts as a semi-permeable filter between its contents and the rest of the body. The membrane’s pore size is quoted between 2- 10 nm (however I cannot find an exact reference & my friendly-neighbourhood-AI-man states that “honey bees have a pore size between 5-8 nm”… but is hallucinating his sources). In the study of Deng & colleagues, they suggest that due to the spacing between peritrophic membranes, a nanoplastic particle has a chance to “enlarge the space to pass through the midgut… and then enter other tissues.” (Deng et al., 2021).
Implications for the Beekeeper: Strengthen the Gut Microbiota
If the gut microbiota is impacted by microplastics, then you should look to supplemental feeding with pro/prebiotics to help the resident microorganisms survive.
Wang and colleagues analysed bees who ingested 25 μm microplastics at a concentration of 50 mg/L, and found that that some plastic particles were “sunken as if they were partially digested…. The hollow structure of the [polystyrene microplastic] is attached clearly by several rod-shaped and spherical-shaped bacterium” (Wang et al., 2021; image below). Moreover, when bees had their gut bacteria manipulated via antibiotics, microplastic exposures led to lethal outcomes… A concern worth noting for those using tetracyclines for the treatment of EFB.
Fortunately, laboratory conditions do not reflect those out in the field. Unless your bees are living next to that incinerator and microplastics are a concern, you can supplement hives with gut-promoting feeds. Various prebiotics are available on the market, with the brand SuperDFM advertising “designed to detoxify pesticides”. We’ll find out in a few years if this also extends to microplastics.
Smaller-Sized Microplastics Increased Viral Infection Susceptibility
Can you spot the trend yet? The smaller the microplastic, the more detrimental its effects. The study of Deng and colleagues examined a combination of polystyrene & Israeli Acute Paralysis virus (IAPV) in both A. mellifera & A. cerana, finding that bees in the microplastic-IAPV treatment groups to have a greater mortality than those without (Deng et al., 2021). The bees were fed 5 μm polystyrene particles, and I wager if they replicated the experiment with the 0.5 μm particle (i.e. 500 nm), they’d see an even more pronounced effect.
Deng and colleagues found an increase in immune gene expressions: hymenoptaecin, defensin 1, and PGRP-S2, indicating that the polystyrenes trigger an immune response in bees (Deng et al., 2021). When these bees were challenged with IAPV, the plastic-treated group had worse outcomes than those treated with IAPV alone, suggesting that if a microplastic-burdened worker was parasitised by an IAPV-carrying Varroa mite, they would have poorer outcomes compared to an otherwise-healthy bee injected by Varroa.
Implications for the Beekeeper: Perform Pest & Disease Management via Strong Colonies
In general, I suggest looking to other treatment approaches before resorting to antibiotics; let the bees overcome illness themselves: supplemental feeds with probiotics, or the shook swarm method or even requeening. If you have the luxury of adding extra brood frames from donor hives, do that too. For Varroa control, opt for “less stressful” approaches like oxalic acid vaporisation rather than formic acid (which kill your queen and make circumstances even more dire [speaking from experience]).
There is an emerging pattern to managing any disease, pest, pesticide, microplastic or greedy- second-cousins-who-beg-you-for-honey: keep a strong colony, either through good genetics, effective supplemental feeds and/or deploying two brood boxes per hive; larger worker populations can withstand higher degrees of stressors.
Routes of Microplastic Exposure
We start with the soil: microplastics can infiltrate the soil vertically (e.g. moving downward as they leach with contaminated water) and horizontally (moving across the soil surface via wind, tillage, surface runoffs; reviewed in El-Sherif et al., 2022). Once in the soil, they are taken up by plant roots, with smaller particles being integrated into the body. This integration is nothing new, as plants are known to absorb hazardous substances (heavy metals, antibiotics), which are then transferred to their consumer.
The size of the microplastic determines its absorption by the plant- the smaller the particle the more likely it’s to be transmitted from root to leaf. The review by El-Sherif & colleagues cite that a 36 nm particle was more likely to spread into wheat leaves, whereas those 40-140 nm remained in the root system, and anything larger was not absorbed (El-Sherif et al., 2022).
Bees are Exposed to Microplastics from Plants, Air, Soil & Water
Most bee exposures to microplastics will be oral2, as the forager gathers nectar and water (both for personal consumption and transport back to the hive). Inside the hive, pollen and nectar will be distributed to the nurse bees and larvae, as well as the queen when contaminated nurses make royal jelly. Microplastics ingested with nectar, pollen, or water can spread during trophallaxis, and the tiny particles in regurgitated droplets may be embed in newly-secreted wax scales as workers produce comb (Alma et al., 2023).
There are many forms of microplastic residues, and here I name Five Fs: Fibers, Filaments, Fragments, Film & Foam, with the first three being most likely to be found in bee products (e.g. Edo et a., 2021 or Diaz-Basantes et al., 2020). As with the plants above, the smaller the microplastic size, the greater its effect on bees (Wang et al., 2022).
Why Isn’t There Much Research on Microplastics in Propolis?
Mainstream awareness of environmental microplastics started in the early 2010s, and I reckon the research progressed slowly due to “competition” with pre-existing fields like commercial beekeeping or pests & disease or the gut microbiota. As of article publication, a Google Scholar search yielded one result for “Microplastics, propolis OR resin, bees” – that of Kadarsah & colleagues, documenting the concentrations of microplastics in bee products from the native Indonesian stingless bee Heterotrigona itama (Kadarsah et al., 2025).
We don’t consume propolis as much as honey/wax/pollen, so there is less economic incentive to study it. Oddly enough, propolis extracts are widely used in Africa as an alternative to pharmaceutical medicines for wound healing and general wellbeing, however those countries are also the least likely to embark on a “12-month observation on the levels of microplastics in propolis extracted from my family’s rather-aggressive Apis mellifera scutellata hives”.
No Current Studies on the Effects of Plastics on Drones & Queens
Published research on microplastics in bees only started in the 2020s – before that we knew that microplastics had an impact on the environment (and just about any living thing). I wager that it was this 2020 paper about microplastics being found in Ecuadorian honey that caused the beekeeping world to go “hang on, what about my area?”.
All of this is to say that there are no direct studies that examine the impact of microplastics on drones & queens. The majority3 of their microplastics would be obtained orally via trophallaxis from nurse bees, who in turn would have used contaminated nectar/pollen to generate the royal/worker jellies for feeding other bees. What I would like to know is how the plastics would change as they move from the gut to the hypopharyngeal gland and then as a royal jelly secretion- How does that impact the jelly’s content/generation and the health of the nurse bees? As we’ve seen above, the smaller the plastic particle, the greater the impact. Could nanoplastics overwhelm a nurse’s ability to produce jellies?
Microplastics in Honey for Human Consumption
This article concludes with a “yes microplastics are in honey that’s sold for use human consumption”.
One study from Kosovo analysed 28 samples of honey and found “microplastics were in the size range of 20-541 µm and had two different shapes (fiber and fragment)… [there were] five different polymer structures (polypropylene, polyethylene terephthalate (PET), ethylene vinyl acetate (EVA), polyethylene (PE), and nylon-6)” (paraphrased from Ozcifci et al., 2025).
The stingless bees (who produce much less honey than A. mellifera) also had traces of microplastics in their samples (Rani-Borges et al., 2024). The authors studied honey produced by urban hives of Melipona quadrifasciata, in Brazil and identified fibers of polypropylene, PET, PE & Polystyrene to be the most prevalent honey contaminates.
The prior article from Ocifici & colleagues compared the microplastic content from honey to that from other sources, and found that in Kosovo, the average microplastic intake from honey is lower than other fooss (extracted from Ozcifci et al., 2025):
- The mean daily and annual intake of microplastics from honey consumption of an individual living in Kosovo was calculated as 0.37 ± 0.20 (0.061.08) MPs/day and 136 ± 75 MPs/year, respectively
- Microplastic intake from milk, soft drinks, mineral water, bottled water, table salt, fruits and vegetables, and fish consumption has been described as 77, 153, 483, 483, 400, 150, 3675, and 337–350 MPs/year, respectively
Do Not be Concerned with Microplastics in Honey
Albanian serving sizes aside, honey as the primary source of microplastics is not a cause for concern. Consider that we can down litres (even gallons!) of milk or softdrink in a day, eat kilograms of seafood, fruits and drink bottled water to our heart’s content… yet struggle eating two tablespoons (~40g) of honey in a single sitting. It’s good to know that microplastics in honey may be lower than other sources, and perhaps this is due to the complexities involved in integrating microplastic from a flower into a bee’s body and then into a capped honey comb.
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Foonotes
- In The Real World™, the microorganisms found on a microplastic surface reflect their environment. For example, suppose you recklessly destroyed your polystyrene hive boxes after finding out they’re contaminated with the AFB-causing Paenibacillus larvae. As your box breaks down due to the actions of water, earth, fire, air, stray cats, your nephew’s squeaky shoes, etc…, the P. larvae spores persist on the plastic’s surface.
Hypothetically, this micro-sized plastic may find itself in a body of water that a forager would gather from, and when that contaminated load is distributed inside the hive for the purposes of cooling, the AFB spores go “surprise!” and settle on the hive body. It’ll be a matter of time until it’s picked up by a worker bee who’ll then transfer it to a nurse bee, who then transfers it to a larva and just like that you have an AFB infestation.
I state this hypothetical because in practice there are too many “moving parts” for the disease to spread … and yet, the “discussion” sections of academic papers would make it seem like an everyday occurrence! ↩︎ - Respiratory exposure is also possible, only harder to measure. The size of a honey bee spiracle is ~ 60 μm, which is enough to allow the small airborne plastics into the respiratory system via inhalation. Once it enters the haemolymph it progresses to the other organs and the hazard progresses. ↩︎
- Inhalation via the spiracles is less of a cause for queens (who’ll take a few mating flights once in her life) and for drones, who would die upon successfully mating with a queen… Imagine if a postmortem on a drone with a ruptured abdomen. If you detected microplastics in his body, would you conclude that he died due to plastic poisoning rather than high-quality sexytime? Of course not! ↩︎