Experts are warning that your favourite tea bag could be releasing billions of microscopic plastic particles into your daily cup, raising fresh concerns about potential long-term health effects.
Scientists say tea bags can shed large numbers of microplastics and nanoplastics when steeped in hot water, although the full impact is still being investigated.
A new review of 19 studies by researchers in Iran and the UK suggests a single dry tea bag may contain around 1.3 billion plastic particles. When brewed, that figure could rise to as many as 14.7 billion as heat breaks materials down into even smaller fragments.
Tea bags made from nylon and PET, or polyethylene terephthalate, were found to release particularly high levels of particles when exposed to near-boiling water. Researchers believe contamination may come from the tea bag material itself or from manufacturing processes.
Microplastics have already been detected in human blood, lungs, liver and other tissues, prompting questions over whether repeated exposure could lead to accumulation in the body over time.
Scientists stress that the long-term health consequences are not yet fully understood, but laboratory studies have suggested possible links between microplastic exposure and inflammation, oxidative stress and cellular damage. However, no direct causal link to specific diseases has been confirmed.
One of the main routes of exposure is through eating and drinking. Tea brewed with plastic-containing tea bags may therefore be one source of ingestion.
Once inside the body, microplastics are small enough to pass through the digestive system, and in some cases may interact with tissues. However, researchers say the extent of absorption and any long-term effects remain unclear.
Experts warn that your favourite tea bag could be releasing billions of microscopic plastic particles into your daily cup
A 2024 study from scientists at the Universitat Autònoma de Barcelona found that polypropylene tea bags were among the worst offenders, releasing approximately 1.2 billion particles per millilitre under laboratory conditions, with some particles small enough to interact with cells.
Most were absorbed by mucus-producing cells in the small intestine, while some were reported to be small enough to potentially reach the cell nucleus, where genetic material is stored.
Although many of the UK’s most popular tea brands describe their products as ‘plastic free’, a recent analysis from Which? suggests this is not always accurate.
Of 28 popular brands examined, only four were found to be fully plastic free.
Historically, tea bags were sealed using a small amount of oil-based plastic called polypropylene to keep them intact. Many brands have moved away from this, but it has often been replaced with polylactic acid, or PLA, a plant-derived bioplastic.
While PLA is marketed as biodegradable, experts note it is still a form of plastic. Consumer groups say this means some ‘plastic free’ claims may be misleading.
More controversially, some products are also labelled ‘microplastics free’, despite PLA potentially breaking down into microscopic particles when exposed to hot water.
The analysis identified PLA in own-label tea bags from major supermarkets including Aldi, Asda, Lidl, M&S, Morrisons, Sainsbury’s, Tesco and Waitrose.
Research from the Universitat Autònoma de Barcelona warns that one tea bag can shed billions of microplastics and most of them are taken up by mucus-producing cells in the gut
Well-known brands including PG Tips, Tetley, Typhoo, Yorkshire Tea, Teapigs, Brew Tea Company and Good Earth were also flagged as using plastic-related materials in at least some products.
By contrast, brands such as Dragonfly, Hampstead, Pukka and some Twinings tea bags were identified as plastic free in certain formats.
However, even within brands offering plastic-free options, some tea bags were found to contain PLA in specific designs such as pyramid or pillow-style bags.
Tetley herbal tea bags were among the few products found to contain conventional polypropylene plastic.
Researchers say concern centres on what happens during brewing, when tea bags are exposed to heat, water and agitation.
Some studies suggest PLA may break down more readily in hot conditions, potentially increasing the release of microscopic fragments.
Previous laboratory research from scientists in Spain found that polypropylene tea bags could release extremely high numbers of particles under controlled conditions, some small enough to interact with cells.
Microplastics are currently being studied for potential biological effects, including oxidative stress, inflammation and disruption of the gut microbiome.
However, researchers emphasise that evidence in humans is still limited and the long-term health impact remains uncertain.
Scientists say microplastics are now widespread in the environment and cannot be avoided completely, but exposure may be reduced by switching to loose leaf tea or choosing tea bags confirmed to be plastic-free.
