Microplastics in tea bags are tiny plastic particles released into the cup when bags made from polymer materials (nylon, polyethylene terephthalate, polypropylene) are steeped in hot water. The issue affects pyramid-shaped "silken" tea bags most — the premium-looking format common in specialty tea brands — and to a lesser extent some heat-sealed paper bags that contain plasticised seals or wet-strength chemicals.
The science on microplastics in food and water has moved fast since around 2018, and tea bags entered the conversation prominently after a now-famous study from McGill University in Montreal. This guide covers what that study and follow-up research actually measured, what the current health-effect evidence shows (with appropriate caveats), and how to drink tea without worrying about it.
The McGill 2019 study (the headline finding)
Published in Environmental Science & Technology by Hernandez and colleagues (PMID 31552738), the McGill study did something straightforward: take commercially available pyramid-shaped tea bags, cut the tea out, place the empty bag into 95 °C water (typical brewing temperature), and measure what particles came out.
The result: a single plastic teabag released approximately 11.6 billion microplastic particles and 3.1 billion nanoplastic particles into a single cup of water. The researchers noted these levels were "several orders of magnitude higher than plastic loads previously reported in other foods" — meaning that, gram for gram, plastic tea bags shed far more microplastic into your beverage than (for example) bottled water or seafood.
The plastics involved were food-grade — typically nylon-6 (NY6) or polyethylene terephthalate (PET, the same plastic used in soft-drink bottles). "Food-grade" means approved as packaging that can contact food, which is a regulatory category — not the same as approved to consume as a beverage component.
Subsequent research has refined and expanded these findings. A 2023 study (PMC10389239) categorised tea bags by polymer type and measured nanoplastic release rates of approximately:
- Polypropylene (PP) bags: 1.20 × 10⁹ particles per mL
- Cellulose (CL) bags: 1.35 × 10⁸ particles per mL
- Nylon-6 (NY6) bags: 8.18 × 10⁶ particles per mL
Cellulose-based bags (a common "compostable" alternative) release substantially fewer particles than polypropylene but are not zero. This is one reason "biodegradable" or "plant-based" tea bag claims need closer reading — the bag may be compostable in the right facility but still shed particles into hot water.
The health-effect research (what we know vs what we don't)
This is where honesty matters more than headlines. The McGill 2019 study tested whether the released particles affected the development and behaviour of Daphnia magna (water fleas commonly used in toxicology research) and found "dose-dependent behavioural and developmental effects". That's a meaningful early-stage signal but it's an invertebrate model, not human data.
Subsequent research has provided more direct human-cell evidence:
- A 2023 study demonstrated that nanoplastic particles released from tea bags can be absorbed by human intestinal cells in laboratory conditions, with uptake depending on cell type and chemical composition. This is the first time direct human-cell uptake of teabag-derived plastics has been shown.
- Cell-culture and animal studies suggest microplastics and nanoplastics may contribute to oxidative stress, low-grade inflammation, immune dysregulation, gut barrier changes, and endocrine disruption. These are biologically plausible mechanisms, observed in controlled experiments, not clinical outcomes in humans.
- A 2023 review published in Foods (PMC10389239) summarised health risks posed by microplastics in tea bags — and was clear that long-term human health consequences remain uncertain. The current evidence supports a precautionary case for avoidance, not a quantified disease-attribution case.
Compared to the air pollution literature (where decades of human cohort data exist), microplastics research is at a much earlier stage. We don't yet have long-term human studies showing that drinking tea-bag tea causes specific health outcomes. What we have is:
- Strong evidence that microplastics are released, in large quantities, from many tea bag types
- Strong evidence that those particles can be absorbed by human cells
- Plausible mechanistic evidence (in cells and animals) that exposure may cause biological harm
- No definitive long-term human outcome data — yet
The reasonable position: this is a category of exposure where the precautionary principle applies. Avoid it where avoidance is easy. For tea, avoidance is genuinely easy — switch to loose leaf.
Per-tea-bag-type breakdown: which are the worst?
| Tea bag type | Material | Microplastic release | Recommendation |
|---|---|---|---|
| Pyramid "silken" bags | Nylon-6, PET | Highest (billions per cup) | Avoid |
| Round/square heat-sealed bags | Paper + polypropylene seal | Moderate (PP shed from seal) | Avoid heat-sealed if you can identify them |
| Stitched/string-and-tag paper bags | Paper only (sometimes treated) | Lower (paper fibres + possible chemical residues) | Better than plastic, not zero |
| "Compostable" PLA / cellulose bags | Plant-based polymer | Lower than nylon/PET, not zero | Better, but still some shedding |
| Loose leaf in stainless steel infuser | None (no bag) | Zero | The reliable solution |
The simplest visual rule: if the tea bag has clear-plastic-feeling crinkly walls (the "silken" pyramid format), it's almost certainly nylon or PET. If it's a soft, opaque, paper-feeling bag with a string and a paper tag, it's probably mostly paper — better, but not perfect.
Why hot water makes this worse
Microplastic release from polymer materials is temperature-dependent. The McGill researchers tested at 95 °C (typical brewing temperature for black tea), and that's roughly the worst case for plastic shedding from food-contact materials. Compared to room-temperature water (where these same bags release far fewer particles), 95 °C water:
- Increases polymer chain mobility, releasing more surface particles
- Accelerates hydrolysis of certain polymer types
- Extracts plasticisers and other additives more efficiently
This is also why studies on plastic baby bottles, plastic kettles, and plastic food containers tend to show worse results when used with hot liquid than cold. Tea bags are a particularly clear case because they're specifically designed to be steeped in near-boiling water for several minutes. Compared to, say, a plastic-lined coffee cup that holds hot liquid for 10 minutes, a pyramid tea bag has more direct extraction.
What about phthalates and other additives?
A 2023 study published in Environmental Science and Pollution Research (PMID 37697202) measured both microplastics and phthalate esters released from tea bags — finding that some plasticiser compounds also leached into the brew alongside the particle shedding. Phthalates are a separate concern from the particles themselves, with their own (longer-running) literature on endocrine effects.
This isn't a reason to panic about every tea bag you've ever used — but it's another data point in the precautionary case for switching to loose leaf where you reasonably can.
What to do: practical guidance
1. Switch your daily tea to loose leaf
This is the highest-leverage change. A single $10–25 stainless steel infuser basket lets you brew loose-leaf tea in any standard mug — no plastic exposure, no shed particles, no phthalates. The total time investment is roughly 30 extra seconds per cup. Compared to switching to glass food storage or filtering your tap water, switching to loose-leaf tea is one of the easiest microplastic-reduction interventions in a typical kitchen.
For more on the loose-leaf transition, see our complete loose leaf tea guide — including which O2H teas work well as starter purchases for tea-bag drinkers.
2. If you must use bags, choose paper string-and-tag over pyramid silken
Standard paper tea bags with a string and tag (the old-fashioned format) shed less plastic than the premium-looking pyramid silken bags. They aren't perfect — paper bags often contain heat-sealed plasticised seams or chemical wet-strength treatment — but they're a meaningful step better than nylon pyramids.
3. Brew at lower temperature where the tea allows
If you're brewing green or white tea (which want lower temperatures anyway — typically 75–85 °C), the lower brewing temperature reduces plastic shedding compared to the 95 °C tested in the McGill study. This won't fix the issue, but it reduces it.
4. Don't store leftover bagged tea in the bag in hot liquid
The longer the bag sits in hot water, the more particles release. If you make a pot of bagged tea, remove the bags as soon as steeping is complete — don't let them sit in the pot.
5. Read your tea bag's material disclosure
Some brands now explicitly disclose tea bag material on packaging or websites. "Plant-based" or "compostable" usually means PLA (polylactic acid) or cellulose — better than nylon/PET but not zero. "Heat-sealed" usually means a polypropylene seal. "Stitched" means no plastic seal but possible plastic in the tag thread. None of these are perfect; loose leaf remains the only zero-plastic option.
What we do at O2H
O2H TEA sells exclusively loose-leaf tea — no tea bags, no pyramid sachets, no plastic infusion devices. Our packaging is designed for shelf-stability and biodegradability: opaque tins or sealed pouches that protect the tea quality without putting plastic in contact with the brewed liquid.
If you're new to loose leaf, our most approachable starting points are Peach Mountain ($21.50 / $19.50) and Sakura Blossom ($21.50 / $19.50) — fruit-scented oolongs that drink easily with a basic infuser.
FAQ
Do all tea bags have microplastics?
No — pyramid "silken" tea bags made from nylon or PET are the worst offenders, releasing billions of microplastic particles per cup according to the McGill 2019 study. Standard paper string-and-tag tea bags release fewer particles, though they're not completely plastic-free either (heat-sealed seams or wet-strength chemicals are common). Loose leaf brewed in a stainless steel infuser releases zero microplastics.
How many microplastics are in a cup of tea-bag tea?
The McGill 2019 study (Hernandez et al., Environmental Science & Technology, PMID 31552738) measured approximately 11.6 billion microplastic particles plus 3.1 billion nanoplastic particles released by a single plastic teabag steeped at 95 °C. Numbers vary substantially by bag type — paper bags release far less, cellulose bags somewhere in between.
Are microplastics in tea bags actually harmful?
The honest answer: we have strong evidence that microplastics are released, that they can be absorbed by human cells, and that they cause measurable biological effects in cell-culture and animal studies (oxidative stress, inflammation, gut barrier changes, possible endocrine effects). We do not yet have long-term human cohort data quantifying disease outcomes. The precautionary case for avoidance is reasonable; the alarm case is premature.
Are "compostable" or "plant-based" tea bags safer?
Better than nylon/PET pyramid bags, but not zero. Studies have measured cellulose-based bags releasing around 1.35 × 10⁸ nanoplastic particles per mL — fewer than polypropylene but still meaningful. "Compostable" is also a regulatory term that requires industrial composting facilities; it doesn't mean no shedding into your tea while brewing.
What's the easiest way to avoid microplastics in my tea?
Buy a $10–25 stainless steel mesh infuser basket and a pouch of loose-leaf tea. Pour 2 g of tea into the basket, add hot water to your standard mug, steep for 3–4 minutes, drink. That's the entire workflow change. No plastic, no shedding, often better-tasting tea, and frequently cheaper per cup once you factor in multi-steep extraction (loose leaf often gets 3–6 cups from one measure).
Does brewing at a lower temperature reduce microplastic release?
Yes, somewhat. The McGill study tested at 95 °C — the worst-case brewing temperature. Green and white teas brew best at 75–85 °C, which reduces (but doesn't eliminate) plastic shedding. For black tea, oolong, and pu-erh — which want near-boiling water for proper extraction — temperature reduction isn't a useful workaround.
Sources cited in this article
- Hernandez, L. M. et al. (2019). "Plastic Teabags Release Billions of Microparticles and Nanoparticles into Tea." Environmental Science & Technology, 53(21), 12300–12310. PMID 31552738
- "Health risks posed by microplastics in tea bags." (2023). Foods. PMC10389239
- Microplastics and phthalate esters release from teabags into tea drink (2023). Environmental Science and Pollution Research. PMID 37697202
- McGill University Newsroom — "Some plastic with your tea?" (2019 study release)
- Teabag-derived micro/nanoplastics study (2024) — surrogate exposure measurement, Science of the Total Environment
Spoke #2 in the Loose Leaf 101 series. See also: Loose Leaf Tea: A Complete Guide for Tea-Bag Drinkers (the pillar hub) and Does Tea Expire? Shelf Life by Tea Type.
