A looming honey bee threat: colorful little microplastic particles

You eat them. Fish eat them. Even birds and frogs eat them. In fact, we all scarf them down like condiments. And when we’re not busy swallowing colorful bits of plastic, we inhale them, sending beads and fragments into the deepest recesses of the human lung.¹ From there, some of the smaller particles ride the waves of our circulatory system as if it were a high-tech water park with twists and turns, slides and slumps.²

If all of us earthlings bathe in a soup of foreign particles, honey bees do, too. I’m referring to microplastics, those tiny but ubiquitous pieces of trash that we’ve unleashed into every known environment, from the bottom of the sea to the top of the highest mountain.³

The news on these stable compounds is not good. So far, most of the research on microplastics has centered on the oceans where they proliferate throughout the food chain. But a recent study even found pigmented microplastics in human placentas, potentially interfering with normal fetal development.⁴ And if they damage fish, clams, and crabs, if they foul the intestines of birds and frogs, what are they doing to our bees? The fact is, we know little.

What is a microplastic?

Microplastics are tiny pieces of plastic debris — chunks and shreds measuring less than 5 mm long — that move willy-nilly throughout our environment. Their smaller next-of-kin, the nanoplastics, which measure less than 1 mm, often accompany the larger particles. Both types are small enough to float in the air and water, worm their way through tiny filters, and remain invisible to most of the creatures that consume them.

When we think of plastic waste, we often picture the big stuff: water bottles, milk jugs, produce boxes, and shopping bags. Microplastics, at least in part, derive from these larger things as they decompose. One of the most alarming sources is car tires that shred slowly as they wear against the pavement and produce countless airborne particles. But we make some microplastics from scratch, such as the synthetic fibers of our clothes, carpets, rainwear, and shoes.

The shape of microparticles matters

Researchers have found that the shape of the particles influences their behavior inside the bodies of animals. Spherical shapes roll over each other, slipping and sliding like marbles. Since they don’t form mats or clogs, they are less destructive to living organisms. But many microparticles are fibers and irregular fragments that stick together and form blockages. Long threads can coil and capture other particles in a net-like wad. Flat fragments may stick like Velcro instead of sliding past each other, and they sometimes have rough or sharp edges that can tear into living cells.

We know microplastics damage birds and fish by accumulating in their digestive tracts. They may consume the particles directly from the water, but more likely they consume them in the bodies of their prey. Larger animals eat the smaller ones after the smaller ones consumed microplastics from water or soil.

The guts of aquatic invertebrates, whose larval stages often eat tiny waterborne flora and fauna, ooze with rainbow bits of plastic. And as you might expect, filter feeders such as mussels, clams, and oysters can be rich sources of plastic for larger animals to feed on.

A scary mix of plastic and all the additives

Another worrisome aspect of microplastics is the chemical additives that go into them. For example, plasticizers that provide certain qualities are added during manufacture. Depending on the application, the plastic may need to be stiff, soft and pliable, or transparent. An array of plasticizers help achieve these goals.

In addition, other chemicals — not defined as plasticizers — used in the manufacture of plastics may be dangerous to living things. Bisphenol A, for example, used to produce polycarbonate plastic and epoxy resins, has been scrutinized for several years as a potential endocrine disrupter.⁵

Regardless of their purpose or classification, many of these substances migrate into the environment as the material degrades. What worries scientists is our lack of knowledge of how these particles and leachates affect the life forms that consume and breathe them.

The shape of particles also plays a role in the release rate of chemicals. Fragments and fibers have more surface area compared to spheres, meaning they may release their chemical constituents more quickly. A quicker release could increase the dose to vulnerable species.

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Plants store plastics in roots, stems, leaves, and fruits

Some estimates suggest humans consume about 52,000 plastic particles per year and inhale another 74,000.^6,7,8 Although they contaminate the environment where we live — including all sources of air, water, and soil — they also contaminate much of our food.

Research shows that plant roots can absorb plastic from the soil and send it to the vegetative parts of a plant, beginning with shoots and stems.⁹ Once inside the vascular system, plastics can travel throughout the plant, reaching the edible tubers, leaves, and fruits. The smallest particles are then distributed to the nectar, pollen, honeydew, and resins. Soils treated with sludge and manure — a common practice — are especially high in microplastic and nanoplastic particles.

Given the ubiquitous nature of these plastics in plants, it’s not surprising we find them in honey. A study in Ecuador found that 12% of honey samples contained plastic particles, and a study in Denmark found microplastics in honey samples from both suburban and rural apiaries.¹⁰

What do all these synthetic “food additives” mean for the bees? Although the particles are small, so are bees. For reference, the average honey bee worker ranges from 15 to 18 mm long, meaning a 5 mm microplastic fiber could be a third of her length — the equivalent of a six-foot man harboring a 24-inch plastic worm. Of course, the shape of particles will influence how readily they are ingested, but many are fine filaments, much longer than wide, released from synthetic textiles.

A story of a beehive and a dryer vent

Two years in a row, I had a beehive behind our pump house, nestled against the wall. The building contains a thousand-gallon holding tank for water, as well as a washer and dryer. The building is insulated, although an IR camera reveals heat leaks from the intersection of the walls and floor. I figured the heat might be a boon to the bees during our cold, damp winters, so I didn’t worry about it. Nor did I worry about the dryer vent on the opposite side of the building.

During the first year, the colony in that hive produced a bumper crop of honey but collapsed during the winter. My postmortem showed nothing amiss — no obvious disease or distress — so I installed a second colony in the same hive. Once again, it produced masses of honey but died during the winter. I still couldn’t find any obvious reason for the loss, and since the rest of my colonies were fine, I gave up on that location.

Were my bees overwhelmed with microparticles?

But now, years later, I wonder if the dryer vent had something to do with it. According to a recent study, a residential dryer vent can release over 560,000 microfibers in 15 minutes of spinning.¹¹ Without knowing it, I probably exposed my bees to countless microfibers during the long winter. Even though the vent was on the opposite side of the building, it wasn’t far from the hive.

The plastic particles could have been inhaled by the bees and accumulated in their airways, or they could have been ingested and interfered with the digestive system. Everything inside a hive is sticky, including honey, nectar, pollen, propolis, wax, and resins. Even brood food is gooey, and bee hairs are designed to capture small particles. You can easily imagine tiny dust-like specks adhering to any of these substances and later being eaten, groomed, or cleaned by bee tongues.

Of course, I don’t know if it was relevant in this case. However, I now think we should factor microplastics in with all the other bee-deleting possibilities. In fact, you can add it to the infamous P-list: pathogens, parasites, pests, predators, pesticides, pollution, and now plastics.

Problems microplastics can bring to bees

Most of the research on microplastic pollution has centered on aquatic and marine environments. But when I wonder about how bees will handle the influx of plastics into their aerial world, the following issues come to mind:

Drinking water

Foraging bees can ingest microplastics from the water they drink. According to research, no bodies of water are free from microplastics. Since microplastics are small enough to travel via wind currents, they can be deposited anywhere on earth and then washed into streams, rivers, lakes, reservoirs, and ponds. Raindrops, too, collect plastic as they fall to earth, carrying the pieces into the soil where plants and soil-borne organisms absorb them. How much plastic can a bee safely drink?

Delicate wings

I also wonder about bee wings. Flying in an atmosphere rich with plastic pieces must be a dangerous practice, a bit like flying a jet through a flock of geese. I imagine that a membrane as thin and delicate as a bee’s wing would take a beating from stuff in the air, especially considering how fast a bee’s wing moves — something close to 230 beats per second — and how sharp some particles may be.

A life raft for pathogens

Some authors have likened wafting particles to life rafts that can spread infection. Pathogens like bacteria and viruses may adhere to the surfaces of plastic particulates and get a free ride to somewhere else, like a flower or a neighboring beehive. More floating particles mean more free rides.

Electrostatic charges

When bees fly, they accumulate a positive electric charge on their bodies. Flowers have negative charges. Because bees are able to detect the negative charges surrounding flowers, they can easily find sources of pollen and nectar.

But what if the electromagnetic charge of bees attracts nanoparticles from the air? What if a bee’s body becomes coated with particles as it flies? Might such particles interfere with flight? Could they interfere with flower detection? Could they inhibit the finding or collection of pollen as the bee becomes overloaded with plastic?

Larval food

And what if the pollen load becomes contaminated with particles? Can the bees separate these particulates from the pollen or do they end up in the bee bread and royal jelly that will feed larval bees? How dangerous are plastic particles to developing bees?

Winter bees

Most foragers only live about six weeks, and perhaps that’s not enough time to see adverse effects from plastic buildup. But what about winter bees? Depending on latitude and elevation, some winter bees may live up to nine months and be responsible for getting a colony through the winter. But what if plastics in the gut or respiratory system shorten their lifespan? Could a colony make it through the winter?

We need more research on how microplastics affect insects

Clearly, potential problems exist but, for now, we don’t know how disruptive microplastics are to bees and other pollinators. So far, only one study has shown microplastics to have an adverse effect on honey bee health.¹² That limited study revealed that accumulated polystyrene particles correlated with reduced diversity in honey bee gut flora and fauna. It also showed changes in gene expression “related to oxidative damage, detoxification, and immunity.”¹³

Another question is how these particles behave within the environment. Will other pollutants, such as insecticides, fertilizers, or metals, react with the plasticizers to produce dangerous synergistic effects? All of this is still unknown.

The bad news is that, by many estimates, plastic production is just getting started. Various environmental groups estimate that production will increase by 40% within the next decade and will triple today’s levels by 2050. It’s time we pay attention.

Rusty
Honey Bee Suite

References

1. Jenner, L.C., Rotchel, J.M., Bennett, R.T., Cowen, M., Tentzeris, V., Sadofsky, L.R. (2022). Detection of microplastics in human lung tissue using μFTIR spectroscopy. Science of The Total Environment, 831, 154907. https://doi.org/10.1016/j.scitotenv.2022.154907.
2. Leslie, H.A., van Velzen, M.J.M., Brandsma, S.H., Vethaak, A.D., Garcia-Vallejo, J.J., Lamoree, M.H. (2022). Discovery and quantification of plastic particle pollution in human blood. Environment International, 163, 107199. https://doi.org/10.1016/j.envint.2022.107199.
3. Carrington, D. (2020). Microplastic pollution found near the summit of Mount Everest. The Guardian. https://www.theguardian.com/environment/2020/nov/20/.
4. Ragusa, A., Svelato, A., Santacroce, C., Catalano, P., Notarstefano, V., Carnevali, O., Papa, F., Rongioletti, M., Baiocco, F., Draghi, S., D’Amore, E., Rinaldo, D., Matta, M., & Giorgini, E. (2021). Plasticenta: First evidence of microplastics in human placenta. Environment International, 146, 106274. https://doi.org/10.1016/j.envint.2020.106274
5. https://www.bisphenol-a-europe.org/wp-content/uploads/2017/04/About-BPA-Myths-Facts.pdf
6. Cox, K.D.; Covernton, G.A.; Davies, H.L.; Dower, J.F.; Juanes, F.; Dudas, S.E. Human Consumption of Microplastics. (2019). Environ. Sci. Technol., 53, 7068–7074.
7. Hartline, N.L., et al. (2016). Microfiber masses recovered from conventional machine washing of new or aged garments. Environmental Science & Technology 50, 11532-11538.
8. Gammon, K. (2022). You eat a credit card’s worth of plastic every week. Nautilus. https://nautil.us/you-eat-a-credits-card-worth-of-plastic-every-week-17950/
9. Li, L.; Luo, Y.; Li, R.; Zhou, Q.; Peijnenburg, W.J.G.M.; Yin, N.; Yang, J.; Tu, C.; Zhang, Y. (2020). Effective uptake of submicrometre plastics by crop plants via a crack-entry mode. Nat. Sustain., 3, 929–937.
10. Edo, C., et al. (2021). Honeybees as active samplers for microplastics. Science of the Total Environment 767,144481.
11. Tao, D., et al. (2022). Microfibers released into the air from a household tumble dryer. Environmental Science & Technology Letters 9: pp. 120-126.
12. Buteler, M., Alma, A.M., Stadler, T., Gingold, AC., Manattini, M.C., Lozada, M. (2022). Acute toxicity of microplastic fibers to honeybees and effects on foraging behavior. Science of The Total Environment, 822. https://doi.org/10.1016/j.scitotenv.2022.153320.
13. Al Naggar, Y., Brinkmann, M., Sayes, C.M., et al. Are Honey Bees at Risk from Microplastics? (2021). Toxics, 9(5), 109. https://doi:10.3390/toxics9050109