Tea bags: a plastic infusion in your cup?
“Plastic in tea water”, ‘it would be better to ban plastic tea bags’, ‘infusion with microplastics’, ‘tea bags release billions of microparticles’. A Canadian study accepted on August 12, 2019 has alerted to the presence of millions of plastic microparticles when plastic tea bags are brewed at 95°c for 5 minutes. But what are these plastic microparticles and why do they cause a reaction?
If there's one well-known way of consuming tea, it's the use of tea bags. These little bags with a string and a label are made from a variety of materials: paper, cotton and, above all, plastic. The advantage of plastic bags is that they can be mass-produced at low cost, and can take many different forms. From simple pouches to high-quality pyramid-shaped “crystal” bags, anything is possible with plastic. And this plastic is made up of microparticles.
But what exactly is a plastic microparticle?
An ant is just a few millimeters long. A microparticle is a thousand times smaller than an ant. These are particles invisible to the naked eye that can be released from plastic. In the case of the plastic tea bag immersed in hot water, the microparticles will be released from the plastic and remain suspended in the water. You can't stop this happening, whatever the water temperature.
So if this happens all the time, what's the problem?
Today, plastic is a major concern for human health, particularly in the food industry. Various scientific studies have already demonstrated the presence of plastics in certain packaged foods (1) or in water from plastic bottles (2). A report issued in 2019 by the CIEL company (3) summarizes the information we know about plastics in humans. The toxicity risks associated with the material itself are numerous: cardiovascular, renal, reproductive, neurological, respiratory, carcinogenic, etc.). There are other sources of risk carried by plastic microparticles. Those released into liquids capture an average of 4% of the toxic additives used in their manufacture. One of the best-known, bisphenol A, was the subject of a health safety report updated by ANSES in 2018 (4). Since 2015, this additive has been banned in the manufacture of baby bottles and bottled water.
So what did these researchers do?
In the name of science ... They went to the supermarket and bought four different brands of tea bags (we won't know the names). They emptied the bags, rinsed them three times to remove all traces of tea and infused them for 5min at 95°C. Once the infusion was complete, their study proceeded in three stages:
- They cut samples of the tea bags after infusion, and used different types of filtration to recover the water and plastic fibers from the bags. Recovering the fibers allows them to see whether the mesh structure of the sachet has remained intact, while recovering the water allows them to validate the presence and size of microparticles. They compared pieces of fiber before and after infusion, using different types of microscopes. The aim: to validate the presence of microparticles.
- Each molecule has a “signature”. This corresponds to the proportion of each component in the molecule. It is possible to detect each component of a molecule and its proportion to be able to identify which molecule we are dealing with. The aim: to provide proof that the microparticles recovered are made of plastic, and to obtain information on the quantity of microparticles in the water.
- There are several ways of testing a molecule's toxicity. Here, the authors exposed a plankton species (Daphnia magna) to the plastic microparticles found in tea bags. In this plankton, changes in morphology and a slower swimming speed are evidence of a toxic effect. The aim: to provide the first evidence of microparticle toxicity.
What conclusions can we draw?
This team of researchers is the first to have demonstrated that plastic tea bags brewed at a time typical of many tea drinkers release plastic micro-particles (nylon and PET, two common plastics). The quantity released is at least 3000 times greater than that found in plastic-packed foods such as table salt. These microparticles are potentially toxic, in this case to living organisms such as plankton (morphological deformation and slower swimming speed).
This study is interesting because it is based on a tea consumption pattern that is consistent with a broad public, and this for different types of bag (including crystal bags, which are considered the best on the market).
More worryingly, they washed the tea bags three times. Unfortunately, they were unable to measure the quantity of microparticles without washing, as the tea molecules would have interfered with their measurements.
However, it's important to bear in mind that we don't know the daily amount of plastic that is non-toxic to the human organism. Today, there are many alternatives for avoiding the use of plastic bags. Cotton bags are becoming more and more popular (although infused cotton should also be tested...). Bulk is undoubtedly the least risky solution, albeit more restrictive.
In any case, don't burn your sachets just yet - consume with discernment!
Bibliography
1 Karami, A.; Golieskardi, A.; Keong Choo, C.; Larat, V.; Galloway, T. S.; Salamatinia, B. The Presence of Microplastics in Commercial Salts from Different Countries. Sci. Rep. 2017, 7, 46173.
2 Pivokonsky, M.; Cermakova, L.; Novotna, K.; Peer, P.; Cajthaml, T.; Janda, V. Occurrence of Microplastics in Raw and Treated Drinking Water. Sci. Total Environ. 2018, 643, 1644−1651.
