Microplastics have widely been found in the environment, in tap and bottled waters, and in some foods.
But researchers at McGill University in Montreal, Canada, led by professor of chemical engineering Nathalie Tufenkji, wondered whether recently-introduced plastic teabags could be releasing micro- and nanoplastics into beverages during brewing.
The research team conducted an analysis on four commercial teas packaged in plastic tea bags.
The team removed the tea from inside the bags to prevent it from interfering with the results, before boiling the bags in water to simulate the tea-making process. Many tea brands now use tea bags marketed as "silken", which are actually made of synthetic materials, such as nylon and polyethylene, so Tufenkji chose to experiment back at the lab.
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McGull University study estimates one cup from a single plastic silken tea bag could contain 11.6 billion microplastic and 3.1 billion nanoplastic particles when placed under hot water. The particles are completely invisible to the naked eye.
These levels were thousands of times higher than those reported previously in other foods, researchers said. Other scientists have raised concerns about microplastics, with an August report from the World Health Organization (WHO) examining the potential human health risks caused by exposure to microplastics in drinking water.
"Tea can be purchased in paper tea bags or as loose-leaf tea, which eliminates the need for this single-use plastic packaging", she said.
But she also said it could be due the fact "it's a piece of plastic being exposed to boiling water" and not just water at room temperature.
PhD student Laura Hernandez, the first author of the study, said more research is needed to understand what effects the particles have on humans. "[And] which is contributing to you not just ingesting plastic but to the environmental burden of plastic".