The Toothbrush Study Everyone Quotes Says the Opposite

MicroPlastics Research DeskEditorial team

August 22, 2026

12 min read

Last reviewed: August 22, 2026 by the MicroPlastics Research Desk. Submit a correction or see our editorial standards.

Quick Answer

There are two confident answers circulating about toothbrushes and microplastics, and the primary sources contradict both of them. The alarming one — “2.3 million microplastic particles a year straight into your mouth” — traces to a real 2025 paper from Jilin University. That paper says, in its own words, that the products tested “do not directly contribute to the health risks associated with exposure to MPs”, and its numbers describe release into the environment, not into you. It also found the leading toothbrush polymer was polypropylene, not the nylon everyone attributes to it. The debunking answer — “bamboo toothbrushes are a scam, the bristles are petroleum nylon” — is contradicted by the manufacturers themselves: Brush with Bamboo states its bristles are 100% castor bean oil, USDA-certified biobased, with 0% fossil fuel and 0% petroleum. That claim is true. The accurate answer is duller and more useful: castor bristles are nylon-11, a genuine polyamide made from a plant. Bio-based describes what went in, not what comes out — and neither nylon-11 nor PA1010 is home-compostable or meaningfully biodegradable. The bamboo brush removes the petroleum and the plastic handle. It does not remove the synthetic polymer touching your teeth.

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Toothbrush bristles and microplastics: what the 2025 Jilin University study actually measured, and why bamboo toothbrush bristles are bio-based nylon rather than petroleum nylon

Key Takeaways

The viral figure is a misquote of a real study. Wang et al. (2025) reported an average of at least 23.3 × 10⁵ — about 2.33 million — particles per person per year from toothbrushes, framed as environmental release.
The same paper reached the opposite conclusion on health, stating that the toothbrushes and toothpastes tested do not directly contribute to microplastic health risks.
It measured polypropylene, not nylon. The toothbrush simulation found polypropylene as the leading polymer at 22%, with 63% of particles under 100 µm.
Toothpaste released fewer particles than the brush — up to 11.83 × 10⁵ per person per year, against at least 23.3 × 10⁵ from the toothbrush.
Hard bristles shed fastest early on. Release climbed rapidly at first and then tapered, which is an argument for softer bristles and for replacing on schedule rather than stretching a brush.
“Petroleum nylon in bamboo brushes” is not universally true. Brush with Bamboo publishes castor-bean bristles at 0% petroleum, and that is a first-party claim about feedstock.
Castor bristles are still nylon. They are nylon-11 (PA11, sold as Rilsan) or PA1010 — plant-derived polyamides that are neither home-compostable nor meaningfully biodegradable.
Boar bristle is the only mainstream fully biodegradable option, because it is animal keratin rather than any polymer. It is not for everyone, and it is not a microplastics emergency that forces the switch.

The numbers, and what each one actually describes

particles per person per year from toothbrushes: 23.3 × 10⁵; the paper’s own figure — about 2.33 million, framed as release into the environment, not ingestion; Wang et al., Ecotoxicology and Environmental Safety, 2025
polypropylene — the leading toothbrush polymer found: 22%; not nylon, which is what most coverage of this study attributes to it; Wang et al., 2025
of released particles under 100 µm: 63%; the size fraction that dominates; smaller particles are harder to measure and harder to dismiss; Wang et al., 2025
petroleum in Brush with Bamboo’s bristles, per the manufacturer: 0%; castor bean oil, USDA-certified 100% biobased — a claim about feedstock, not about whether it is a polymer; Brush with Bamboo FAQ (manufacturer)

The short answer

Yes, toothbrush bristles shed. They are polymer filaments dragged across enamel twice a day under pressure, and abrasion is what makes plastics shed. That much is not in dispute and never was.

What is in dispute is everything built on top of it. The number being quoted at you has been detached from the study that produced it, and the reassurance being sold to you — a wooden handle — does not address the part that touches your teeth. Both of those are worth an article because both are being repeated by people with something to sell.

What the 2025 study actually did

The paper is Wang and colleagues at Jilin University, published in Ecotoxicology and Environmental Safety in September 2025. They surveyed oral-care product use in China, then characterised the microplastics generated by the toothpastes and toothbrushes that survey identified as commonly used, and tracked how release from the brushes changed over time.

Three findings matter, and only one of them travels:

The toothpaste particles were polyethylene and polyethylene-vinyl acetate — 22% and 78% respectively, translucent and irregularly fragmented.
The toothbrush simulation found polypropylene at the highest share, 22%, with 63% of particles below 100 µm. This is the detail that gets lost: the coverage calls it a nylon-bristle finding, and the paper does not.
Release from hard-bristled brushes rose quickly at first, then levelled off. New brushes shed fastest.

The sentence nobody quotes

Then the authors write this: “The results suggest that the use of popular Chinese toothbrushes and toothpastes does not directly contribute to the health risks associated with exposure to MPs.”

And their closing line puts the numbers where they belong: “Continuous daily use of toothpaste and toothbrushes releases large numbers of MPs into the environment.”

So the study measured an environmental load, assessed the personal risk, and found the personal risk not to be direct. The figure of 23.3 × 10⁵ particles per person per year — about 2.33 million — is real, and it is the number that became “2.3 million particles straight into your mouth” in retail copy for boar-bristle brushes. The study does not say that.

Two further limits worth holding. These were Chinese products and a Chinese population, so the polymer mix does not automatically describe a brush bought in the US. And the other numbers circulating — “39 particles every time you brush”, “30 to 120 per brushing” — appear nowhere in the paper. We could not source them to any primary study.

The bamboo argument, and why the debunk is also wrong

The counter-genre is now as loud as the original: posts arguing that bamboo toothbrushes are a scam because the bristles are petroleum-based nylon regardless of the handle.

For at least one major manufacturer that is simply not true. Brush with Bamboo’s own FAQ states its bristles are “100% Castor Bean Oil and USDA Certified 100% Biobased”, containing “0% fossil fuel and 0% petroleum”. That is the manufacturer’s published claim about its own feedstock, and there is no reason to reject it.

The mistake is assuming that settles the question. It answers where the carbon came from, not what the material is.

What castor bristles actually are

Castor-derived bristles are nylon-11 — polyamide 11, polymerised from 11-aminoundecanoic acid derived from castor beans, sold commercially by Arkema as Rilsan — or the related PA1010, built from two castor-derived monomers. Both are genuine members of the nylon family. They are made from a plant and they are still polyamides.

And critically: neither nylon-11 nor PA1010 is home-compostable, and neither meaningfully biodegrades in an ordinary environment. Bio-based is a statement about the raw material entering the process. Biodegradable is a statement about what happens when you are finished with it. They are unrelated properties that share a prefix.

This is the same distinction we draw about PLA in which household materials are actually plastic: plant-based and compostable describe origin and disposal, not behaviour in use. A castor-bristle bamboo brush is a real improvement on fossil feedstock and on a plastic handle. It is not a plastic-free object.

What is actually on the end of your toothbrush (checked August 2026)
Bristle type	What it is	Biodegrades?
Conventional nylon	Petroleum-derived polyamide (nylon-6 or 6/6)	No
Polypropylene	The leading polymer in the 2025 study’s brushes	No
Castor / “plant-based” nylon	Nylon-11 (PA11) or PA1010 — polyamide from castor beans	No — bio-based, not biodegradable
Boar bristle	Animal keratin, not a polymer at all	Yes
Bamboo handle	Genuinely plant material — but it is the handle, not the bristle	Yes (handle only)

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What we still do not know

Nobody has measured shedding from a castor/PA11 bristle specifically. The 2025 work characterised conventional brushes. Whether a bio-based polyamide abrades more, less or the same is an open question, and assuming it behaves like polypropylene would be a guess.
No study has followed particles from brushing into a person. Release into a rinse basin is not the same measurement as uptake, which is exactly why the authors were careful about the health claim.
Electric brush heads are unstudied here, despite higher speed and more contact cycles per session.
The US polymer mix is unknown. A survey of Chinese products tells you what those brushes are made of, not what is in a multipack bought in Ohio.

What to actually do

The mechanism is abrasion, so every useful lever acts on abrasion — and the dental advice and the plastics advice point the same way, which is rare and worth taking:

Use soft bristles and less pressure. The study found hard bristles shedding fastest. Dentists have argued for soft bristles for decades on enamel and gum-recession grounds. Both reasons agree.
Replace on schedule, but do not replace early. Release was highest when brushes were new and tapered with use, so churning through brushes faster is not the win it sounds like. Roughly three months, or when the bristles splay.
Rinse and flick the brush out rather than leaving it wet. Softened, waterlogged filaments abrade more readily.
If you want the plastic genuinely gone, boar bristle is the only mainstream option — animal keratin, no polymer. It is not vegan, it wears differently, and it is a preference rather than a medical necessity.
A bamboo handle is still worth buying if the reason is fossil feedstock and plastic waste. Just do not buy it believing the bristles are plant fibre.
What not to do: switch on the strength of “2.3 million particles into your mouth”. That framing is not what the study found, and a purchase made on a misquote tends not to survive contact with the correction.

Frequently Asked Questions

Do toothbrush bristles release microplastics?

Yes. Bristles are polymer filaments abraded against teeth twice a day, and abrasion is what makes plastics shed. A 2025 study from Jilin University measured release from commonly used Chinese toothbrushes and reported an average of at least 23.3 × 10⁵ particles per person per year — about 2.33 million — with 63% of particles under 100 micrometres. The leading polymer they found was polypropylene at 22%.

Is it true that you swallow 2.3 million microplastics a year from your toothbrush?

No, that is a misquote. The 2.33 million figure is real and comes from Wang et al. 2025, but the paper frames it as release into the environment, not ingestion, and states explicitly that the products tested "do not directly contribute to the health risks associated with exposure to MPs". The "into your mouth" framing was added by retailers selling alternative brushes. Other figures in circulation — 39 particles per brushing, or 30 to 120 — do not appear in the study at all.

Are bamboo toothbrush bristles made of plastic?

They are made of nylon, but not necessarily petroleum nylon. Brush with Bamboo states in its own FAQ that its bristles are 100% castor bean oil, USDA-certified 100% biobased, containing 0% fossil fuel and 0% petroleum. Castor-derived bristles are nylon-11 (PA11, sold as Rilsan) or PA1010 — real polyamides made from a plant. So the common claim that bamboo brushes hide petroleum nylon is not universally accurate, and the claim that they are plastic-free is not accurate either.

Do plant-based or castor oil bristles biodegrade?

No, and this is the most common confusion. Bio-based describes the raw material going into the polymer; biodegradable describes what happens to the finished product afterwards. They are unrelated properties. Neither nylon-11 nor PA1010 is home-compostable, and neither meaningfully biodegrades in an ordinary environment. A castor-bristle brush removes fossil feedstock from the supply chain; it does not leave a compostable object behind.

What is the only truly plastic-free toothbrush?

A wooden or bamboo handle with boar bristle, because boar bristle is animal keratin rather than any polymer, and it genuinely biodegrades. It is not vegan, it softens differently when wet, and many people dislike it. Nothing in the current evidence makes it a health necessity — the study most often used to argue for it concluded there was no direct health risk from conventional brushes.

Do hard or soft bristles shed more?

Hard bristles shed faster, particularly when the brush is new. The 2025 study tracked release over time and found the rate from hard-bristled brushes rising rapidly at first and then tapering with continued use. Soft bristles used with light pressure are also the long-standing dental recommendation for protecting enamel and preventing gum recession, so the plastics argument and the dental argument point the same direction here.

Should I replace my toothbrush more often to avoid microplastics?

No — replacing early is counterproductive on this specific measure. Release was highest when brushes were new and declined as they were used, so shortening the replacement cycle means spending more time in the high-shedding phase. The standard guidance of roughly three months, or whenever the bristles splay, remains right; it is set by cleaning effectiveness and hygiene, which are better reasons than particle counts.

Sources

Wang S, Zheng N, Peng L, An Q, Chen C, Wei Y (2025). Patterns and risks of microplastic release during primary oral care in Chinese residents — toothbrush release averaging at least 23.3 × 10⁵ particles/person/year and toothpaste up to 11.83 × 10⁵; polypropylene the leading toothbrush polymer at 22%; 63% of particles below 100 µm; authors conclude the products "do not directly contribute to the health risks associated with exposure to MPs". Ecotoxicology and Environmental Safety 302:118694.
Brush with Bamboo (2026). Frequently asked questions — "Our toothbrush bristles are 100% Castor Bean Oil and USDA Certified 100% Biobased… our bristles contain 0% fossil fuel and 0% petroleum". Brush with Bamboo (manufacturer).
Arkema (2026). Rilsan polyamide 11 — bio-based polyamide polymerised from 11-aminoundecanoic acid derived from castor beans, the polymer used for castor-oil toothbrush bristles. Arkema (manufacturer).

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