Are tea bags safe to use?

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Intro

In this Brief, we explore the concerns surrounding plastic components in tea bags. Consulting existing studies and expert opinions, we consider the possibility that tea bags shed micro- and nanoplastics when exposed to hot water, and evaluate the potential threat to human health. Finally, we consider the pros and cons of alternative tea formats, including instant and loose-leaf tea.

Key takeaways

• Tea bags were invented in North America in the early twentieth century. While the exact date and inventor behind the innovation is still debated, their popularity has persisted; consumers still find tea bags more convenient than loose-leaf teas, which can be harder to portion and sometimes require additional brewing equipment.
• The plastic components in modern tea bags – primarily thermoplastic sealants and premium bags made entirely from food-grade PET or nylon – have raised concerns of micro- and nanoplastic contamination. The use of epichlorohydrin to prevent paper bags from ripping has also caused concern, as it is considered carcinogenic.
• Researchers have attempted to quantify the scale of micro- and nanoplastic contamination from tea bags. However, the accuracy of their results, as well as the actual threat to human health, has come into question.
• Consumers looking for alternatives may turn to tea bags made from alternative materials. However, studies show that various materials can still leach plastic particles and microfibres when used, and tea bags that fail to distinguish between home and industrial compostability may contribute to contaminated soil.
• The final solution is to avoid tea bags completely. Instant tea offers similar convenience, and while it may come in plastic packaging of its own, it does not make contact with hot water. Alternatively, loose-leaf tea is regularly sold in paper pouches, cardboard containers, or aluminium tins, and tea strainers made from non-plastic materials are widely available.
• Loose-leaf teas can also improve the consumer experience, introducing tea drinkers to traditional brewing methods and maximizing the taste and health benefits of the tea leaves.

Conclusion

Scientists are still studying the health implications of ingesting micro- and nanoplastics, but if consumers are concerned in the meantime, they can turn to other tea formats. While they may sacrifice immediate convenience, consumers should find that instant and loose-leaf teas are readily available and not strenuous to brew.

Studies are starting to warn that tea bags may be leaching microplastics into our cups of tea. Should we be concerned, and if so, are we ready to sacrifice their convenience for an alternative solution? Packaging Europe answers it all in this edition of the Brief.

Legend has it that the tea bag was an accidental invention, attributed to twentieth-century tea merchant Thomas Sullivan after his American clients mistakenly infused his samples inside their silk pouches. Another origin story, this one with a paper trail, credits the invention of the tea-leaf holder – a ‘pocket-like device’ crafted with open-mesh woven fabric and cotton thread – to Roberta C. Lawson and Mary McLaren in 1903.

In either case, the format gained momentum as a straightforward and affordable alternative to elaborate tea sets. So it was that the tea bag’s material composition would evolve with the times; the unpleasant taste of early gauze designs encouraged the creation of hemp fibre replacements, while the demands of mass production gave rise to paper bags.

Keeping the tea leaves sealed is essential to the format’s convenience. Metal staples were an initial solution, but concerns that consumers could swallow loose staples, dissolved metals, or metallic dust have led to redesigns and outright bans. Thus, the heat-sealed bag was invented, oftentimes relying on thermoplastics like polypropylene. A substance called epichlorohydrin may also be used to prevent paper bags from falling apart in hot water.

While consumers still prefer the simplicity, portability, and portion control of tea bags over loose-leaf alternatives, the threat of oligomer migration – i.e., the fragmentation of micro- and nanoplastic (MNP) particles when the tea bag is submerged and stirred – has sparked further fears.

Most paper bags are thought to use plastic fibres in their sealant, with TeaTrade indicating that the average tea bag contains 20-30% polypropylene. ‘Silken’ PET or nylon, usually considered premium products, contain even more plastic. Even epichlorohydrin is considered a carcinogen in animals, although its health implications for humans are still being studied.

Is trouble really brewing?

Researchers have attempted to quantify the scale of plastic contamination. One study indicates that steeping a tea bag made from PET and nylon at 95°C releases approximately 11.6 billion microplastics and 3.1 billion nanoplastics into a single cup. Another has isolated 10 µL of steeped liquid from a total volume of 10 mL, and approximated that one tea bag had released 3.89 million microplastic particles, each thought to be 1 µm² in size.

Others try to calculate the amount of plastic per measurement; a single polypropylene tea bag has been said to release around 1.2 billion tiny plastic fragments per millimitre, and tea bags made from polyester, polypropylene, and polyethylene could reportedly infuse around 13,000 microplastic fragments – each between three micrometres and five millimetres in size – into a single cup of tea.

Studies like these have since come into question. A recent literature review argues that certain findings rely on “exaggerated” numbers of tea bags and extraction times – calculating that, due to the precipitation of oligomers and additives as the drink cools, a 200 mL cup of tea would contain 50 to 115 µg/L of plastic pellet. This figure is thought to be five hundred times lower than the EU’s limit on chemical migration from food-contact plastics (60 milligrams per litre, as per Regulation (EC) No 10/20113).

It is also worth noting that the health implications of MNP exposure are still being researched. Recent investigations have linked exposure to neurological symptoms like fatigue and dizziness, problems with metabolism and nutrition, respiratory problems like asthma and bronchitis, issues with regulating the body’s immune system, ageing-related disorders, and various forms of cancer – but experts have cautioned that the health implications are not definitively proven.

As Hailey E. Hampson, postdoctoral fellow at the University of Southern California and the University of Washington, told the New York Times, a controlled study may require one group of participants to knowingly consume microplastics, which has ethical implications.

Precautionary measures

As the scientific community works to understand the true threat of MNPs, consumers are understandably concerned for their health and seeking ways to avoid contamination.

Mark R. Wiesner, professor of civil and environmental engineering at Duke University, discourages consumers from reheating cold tea with the tea bag inside, as the additional heat could release more plastic into the drink. Conversely, he believes that rinsing the bag under running water could wash some particles away before the tea is even brewed – and pre-washing tea bags in room-temperature water is thought to remove 76%–94% of micron-sized residues and 80%–87% submicron-sized residues, respectively.

Unfortunately, these approaches might come at the cost of the tea’s strength and flavour, and neither negates the environmental impact of microplastics in our waterways.

Consumers may instead opt for tea bags made from alternative materials – but if ingesting plastics is the concern, bioplastic formats may not be the right solution. Many are made from polylactic acid, and a research paper has estimated that one empty filter bag, boiled at 95°C water in a ‘standard’ tea brewing process, still emits one million nanoplastic particles.

Beyond the human body itself, these products are broadly marketed as ‘compostable’ or ‘biodegradable’ but only break down in industrial conditions. While used PLA tea bags were said to degrade by 97.7% in a trial conducted at Envar’s composting facility, another study found that 100% PLA tea bags remain completely intact over twelve months in a home compost environment. Arguably, then, their improper disposal could contaminate fresh produce and water and lead to plastic consumption elsewhere.

The non-plastic approach also relies on the manufacturer’s transparency. Beyond Plastics provides a list of recommended brands for plastic-free tea bags, including Numi Tea, Yogi Tea, and Stash Teas. Each claims to utilize hemp, abaca, and cellulose fibres in their respective tea bags; these materials are not directly edible and may even emit microfibres of their own, albeit far fewer than conventional polymers. Nevertheless, the brands gesture towards various test results and certifications proving the absence of epichlorohydrin, chlorine dioxide, and genetically modified materials in their tea bags.

Where compostability is concerned, certification can be elusive. For example, Numi Tea specifies that its tea bag wrappers are compliant with the ASTM D6868 compostability standard, but no equivalent certification is provided for the bags themselves. They are reportedly made from manila hemp cellulose, and researchers have found that the fibre’s tensile strength decreases by 80% after 90 days in natural soil conditions, but it is unclear whether the bags themselves have been tested.

Pukka also claims to manufacture its bags from a blend of abaca, wood pulps, and plant cellulose fibres, and to replace plastic sealants with organic cotton stitches. Its tea bags were among the 7.3 million samples used in Envar’s industrial degradation trial, but while they are said to be certified as home compostable, the specific certification is not provided on-pack.

The next-best infusion

An alternative solution is to avoid tea bags altogether. The packaging industry is already anticipating, and working to fill, the resultant gap in the market; for instance, PA Consulting has prototyped a ‘tea sheet’, made from lokta pulp and expected to compost at home. Until these new ideas come to fruition, though, individuals can choose from a range of other products.

The convenience of a tea bag is arguably matched, perhaps even surpassed, by instant tea; the powder can be poured into a cup, then mixed with hot water to form the finished drink. This avoids direct oligomer migration, but instant formats often require plastic packaging to keep the product dry before use. While the polymers used are presumably food-grade, it circles back to the issue of microplastics leaching into the earth at end-of-life.

Thankfully, loose-leaf tea is no longer a major luxury. Strainers and infusers readily available on the modern market. Researchers and tea companies alike recommend stainless steel, glass, ceramic, or even cotton formats to avoid MNP contamination; their reusability and subsequent waste reduction are a bonus.

Consumers can increasingly buy their leaves in fibre-based pouches, paperboard containers, and aluminium tins. Some may still be plastic-lined, or else contain the leaves in a plastic pouch to ensure they stay airtight.

As far as consumer convenience goes, loose-leaf teas may stew for longer than their bagged alternatives. The difference is usually a matter of minutes, but Meadow Tea sweetens the deal with its assertion that tea leaves have more space to expand outside a bag – giving the drinker more control over the release of natural flavours and healthy compounds. One group of researchers add that loose-leaf formats bring consumers closer to traditional brewing techniques and enrich the drinking experience.

Indeed, humans were steeping tea leaves for millennia before the invention of the tea bag, and have continued to do so in the meantime. Ultimately, it all boils down to the ever-present balance between the familiarity and thoughtless ease of single-use, versus the proven viability – and, in this case, guaranteed safety – of pre-existing approaches.

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