Bangladesh runs on tea, and a growing share of it is brewed from a bag rather than loose leaves. A new review of 19 scientific studies suggests that habit deserves a second look: when a tea bag meets boiling water, it can release enormous numbers of plastic particles too small to see, along with some of the chemicals used to make that plastic.
What the studies measured
The research focuses on micro- and nanoplastics, together abbreviated MNPs. Microplastics range from one micrometre to five millimetres; nanoplastics are smaller than a micrometre. For scale, a human hair is about ten micrometres across, so none of this is visible in the cup. For bottled iced tea the particles come from the bottle and cap; for hot tea, the review finds, the main source is the bag itself.
The reason is that “paper” tea bags are frequently not just paper. Many use a plastic mesh, and even paper bags often carry a polypropylene layer so they can be heat-sealed. Bags marketed as biodegradable or made from bioplastics were also found to shed particles, though fewer than plastic-mesh bags.
The numbers
One study measured roughly 14.7 billion tiny plastic particles released from a single plastic tea bag; another put the figure at about 1.3 billion per bag. The particles do not travel alone: the additives that make plastic flexible or coloured can leach into hot water, and the studies detected plasticisers and bisphenol-type chemicals in brewed tea.
What it does to the body — honestly
This is where the evidence thins out. No clinical trial has tested the effect of tea-bag plastics on people. Laboratory work is suggestive rather than conclusive: water fleas (Daphnia) exposed to liquid from nylon and PET tea bags developed abnormal body structures and impaired movement, and experiments on models of human gut cells showed the particles being taken up. Whether daily exposure at these levels harms humans over years is an open question, not a settled one.
Practical steps for a tea-drinking household
- Switch to loose leaf with a steel infuser or a plain pot — the simplest way to remove the bag from the equation entirely, and often cheaper per cup.
- If you use bags, prefer ones that state they are plastic-free and heat-sealed without polypropylene; “biodegradable” alone is not that guarantee.
- Avoid squeezing or repeatedly re-steeping a bag in boiling water; higher temperature and mechanical stress increase shedding.
The science does not say a cup of bagged tea will hurt you. It does say we are swallowing plastic we did not intend to, in quantities that were unknown until researchers started counting — and that the fix, for once, is easy.
