The Plastic Experiment.

Your Tea Bag Is Probably Plastic — and Hot Water Sets It Loose

Tea felt like the safest thing I consumed. Leaves, water, done. Humans have been drinking it for thousands of years. What could possibly be wrong with a cup of tea?

The tea bag, it turns out. For most supermarket tea, the bag itself is either made of plastic or held together with it — and the moment you pour near-boiling water over it, it starts shedding plastic particles into your cup by the billions. Not “traces.” Billions.

This is the story of why I stopped using tea bags entirely, what the research actually shows, and how to check whether the box in your pantry is one of the bad ones.

A single tea bag, eleven billion particles

The study that put this on the map came from McGill University in 2019. Researchers took four commercial “silken” plastic tea bags — the premium-looking pyramid kind — emptied out the tea, and steeped the empty bags in 95°C water, exactly the way you’d brew a cup. Then they counted what came off.

One tea bag released about 11.6 billion microplastic particles and 3.1 billion nanoplastic particles into a single cup (McGill University, published in Environmental Science & Technology). At the time, that was thousands of times more plastic than had been measured in any other food or drink.

Two details from that study matter for everyday tea drinkers. First, the bags were nylon and PET — genuine plastic mesh, sold as tea bags. Second, the heat is what does the damage. Brewing temperature is close to boiling, and at 95°C the polymer surface breaks down far faster than it would in cold water. To be precise about the mechanism: the plastic doesn’t dissolve like sugar — the hot water fractures the bag’s surface into billions of micro- and nanoscopic plastic fragments, which end up suspended in your tea, along with whatever chemical additives leach out alongside them. You then drink it while it’s still hot. A tea bag is close to a worst-case design: plastic + near-boiling water + a drink you consume immediately, bag and all steeping for minutes.

The 2024 follow-up: the particles get into your cells

Five years later, a team at the Universitat Autònoma de Barcelona went further. They brewed commercial tea bags made from three different materials and counted the particles released into the infusion (UAB, published in Chemosphere):

  • Polypropylene bags: ~1.2 billion particles per millilitre of tea (average size 137 nanometres)
  • Cellulose (paper) bags: ~135 million particles per millilitre (average 244 nm)
  • Nylon-6 bags: ~8.2 million particles per millilitre (average 138 nm)

Per millilitre. A mug is 250 of those.

Then they did something no tea bag study had done before: they exposed human intestinal cells to the particles. The particles were absorbed — most readily by the mucus-producing cells that line your gut — and for the first time, researchers watched plastic particles enter the cell nucleus, where your DNA lives (Medical Xpress summary). What they do in there is still an open question. That they get in there no longer is.

And if you’re wondering where swallowed particles end up: plastic has now been found in human blood, arterial plaque and brain tissue — I covered that research in detail in my first post.

“But my tea bags are paper”

That’s what I thought too. Here’s the uncomfortable taxonomy of the supermarket tea aisle:

1. Pyramid / “silken” bags — often actual plastic mesh. The shiny, luxurious-feeling ones. Traditionally nylon or PET — the McGill scenario. Some brands have switched these to PLA (more on that in a second).

2. Flat paper bags — usually paper glued shut with plastic. Most standard string-less supermarket bags are heat-sealed, and the “glue” is polypropylene fibre woven into the paper — typically around 2–3% of the bag. It’s a small percentage, but polypropylene was the worst shedder in the UAB study, and it’s sitting in boiling water. If a paper tea bag’s edges are smoothly crimped shut with no staple, no string and no fold, it’s very likely PP-sealed.

3. “Plant-based” and “biodegradable” bags — still plastic, just bioplastic. PLA (polylactic acid, usually made from corn starch) is the industry’s favourite upgrade because it’s not petroleum-based and it’s industrially compostable. But PLA is still a synthetic polymer — a plastic — and research on PLA products shows they shed particles too: in University of Queensland testing published in 2026, PLA-lined “compostable” cups actually released more particles than the conventional plastic-lined ones. “Compostable” is a claim about what happens in a composter, not about what happens in your cup at 95°C.

4. The genuinely plastic-free minority. Folded and stapled bags, stitched cotton bags, or paper certified home compostable with an explicit “plastic-free” claim.

The Australian shelf, roughly

Formulations change, so treat this as a snapshot and check the current box — but as of recent reporting: Twinings Australia moved to certified home-compostable paper-and-cotton-string bags in March 2024 with no PLA; Lipton’s Quality Black uses manila hemp and cellulose, while some of its other ranges have used thermoplastic fibres; Dilmah’s standard bags have been listed at about 2% polypropylene for heat sealing; Nerada states under 2% food-grade synthetic fibre; Madura uses “plant-based” PLA paper; and Bushells bags have contained thermoplastic fibres (brand roundup, Australian guide, 1 Million Women’s guide). The pattern to notice: even “paper” bags mostly aren’t plastic-free — the plastic is just hiding in the seal.

Oh, and it’s not only the bag. If you’re boiling the water in a plastic kettle, University of Queensland researchers showed that adds billions of particles of its own — a brand-new plastic kettle’s first boil released around 12 million nanoparticles per millilitre. The Australian cuppa can pick up plastic twice before the tea even goes in.

What I did instead

This was the cheapest, easiest swap of my entire plastic-free project:

  • Loose-leaf tea. I brew a Japanese organic sencha (YAMASAN, from Kyoto) and a Himalayan loose-leaf green (VAHDAM). Loose leaf is usually better tea anyway — whole leaves instead of the dust that goes into bags.
  • Stainless steel snap-ball strainers. A three-pack of fine-mesh steel infuser balls cost me about the same as two boxes of premium pyramid bags. Spoon the leaves in, snap it shut, brew, rinse. It adds maybe twenty seconds to the process.
  • Steel kettle for the water. Covered in the first post — no plastic anywhere between tap and cup.

Same ritual, same convenience within a rounding error, zero plastic mesh steeping in my boiling water.

Update, spring 2026: the same three pieces of kit turn out to make an even better warm-weather drink with no boiling water anywhere in the process — the overnight cold-brew jug.

How to check the box in your pantry

  1. Look at the shape. Shiny pyramid or “silken” bag → assume nylon, PET or PLA.
  2. Look at the seal. Smooth heat-crimped edges, no staple or string → very likely polypropylene-sealed paper.
  3. Try the tear test. Plastic-mesh bags stretch and refuse to tear cleanly; paper tears.
  4. Read the claims carefully. “Biodegradable,” “plant-based” and “compostable” usually mean PLA — still a plastic. The words you want are “plastic-free” and “certified home compostable” together.
  5. Or skip the question entirely — loose leaf and a steel strainer, and there’s nothing to decode.

I spent years carefully steeping plastic in boiling water and drinking it twice a day, thinking tea was the healthiest habit I had. The tea was never the problem. The bag was.

This is part of my series on getting plastic out of my body — start with the research on what’s already in us, and everything I swapped, or jump to the materials reference for the quick-card version of every material in your kitchen, teabags included.

Sources