Recently, a study by McGill University in Canada showed that tens of billions of plastic particles are released from tea bags at high temperature.
It is estimated that each cup of tea brewed from a tea bag contains 11.6 billion microplastics and 3.1 billion nanoplastic particles. Research published Sept. 25 in the U.S. journal Environmental Science and Technology
They randomly selected four plastic tea bags: two nylon bags, and two PET (polyethylene terephthalate) bags. In particular, PET can be used for a long time in the temperature range of 55-60 °C, and can withstand high temperature of 65 °C for short-term use, and can withstand low temperature of -70 °C, and has little impact on its mechanical properties at high and low temperatures. Throw away the tea leaves, rinse the bag with purified water, and then soak the empty bag in 95°C hot water for 5 minutes to simulate the tea-making process. Obviously, the water we brew tea is boiling water, and the temperature is much higher than the range of PET.
McGill realization shows
First a lot of plastic particles are released
A cup of tea bag can release about 11.6 billion micron-sized and 3.1 billion nanometer-sized plastic particles!
Secondly, heavy metals in tea are absorbed by plastic particles
Tea may contain small amounts of heavy metals such as lead and chromium. Small particles, such as micron and nanoscale plastics, can absorb heavy metals. When the researchers looked at the tea bags, they did find that these tiny plastic particles had adsorbed heavy metals.
Furthermore, are these released plastic particles toxic to living things?
To understand biological toxicity, the researchers used Daphnia, an invertebrate that is a model organism used to assess toxins in the environment. The higher the concentration of tea bags, the less active the water flea swims. Of course, heavy metals + plastics are worse than pure plastic particles. In the end, the Daphnia did not die, but deformed. The study concluded that whether tea bag plastic particles affect human health requires more in-depth research.
So what are the requirements for the inner bag when we buy tea bags?
A: It is best to use corn fiber tea bags, (the cost of corn fiber tea bags will be higher than that of PET nylon). Because corn fiber is a synthetic fiber that is converted into lactic acid by fermentation and then polymerized and spun. Natural, environmentally friendly, degradable, and resistant to high temperatures of 130 degrees. Even brewing with 100-degree boiling water will not be a problem, and corn fiber is degradable, which is also beneficial to the environment.
So how to identify the material of the tea bag you buy?
As mentioned above, tea bags are currently made of non-woven fabrics, nylon, corn fiber and other materials.
Non-woven tea bags are made of polypropylene. Traditionally, many tea bags are made of non-woven fabrics. If they meet the standards, the safety can also be guaranteed. The disadvantage is that the perspective of the tea bag is not strong, and the water permeability is not good. There are harmful substances in the production process of some non-woven fabrics, which may be released during the brewing process.
Nylon tea bags are tough, not easy to tear, and have large meshes. The disadvantage is that when brewing tea, if the water temperature exceeds 90 degrees for a long time, it is likely to release harmful substances.
The easiest way to make nylon tea bags is to burn them with a lighter. After the nylon is burned out, it will turn black. And not easy to be torn.
The same way of corn fiber, after burning it is the color of ash after burning dry wood, some plant fragrance, and corn fiber can be easily torn.
