Researchers at McGill University report that filter media containing polyethylene releases “unusually high” concentrations of plastic nanoparticles, according to McGill Professor of Chemical Engineering Nathalie Tufenkji.
A new study suggests that pyramid-shaped "silken" teabags woven of synthetic polyester and nylon leach billions of tiny plastic particles while steeping tea in boiling water. The segment represents about 5% of the total tea bag materials market.
The American Chemical Society’s Journal of Environmental Science & Technology published the surprising findings in September.
Tufenkji explained that researchers purchased four different commercial teas packaged in plastic tea bags. The researchers cut open the bags, removed the tea leaves and washed the empty bags. Then, they heated the teabags in containers of water to simulate brewing conditions. Levels were thousands of times higher than those reported previously in other foods. In another experiment, the researchers treated water fleas with various doses of the micro- and nano-plastics from teabags. Although the animals survived, they did show some anatomical and behavioral abnormalities. Micro-plastics up to 100 microns in size and nano-plastics at 1,000 nanometers are not known to harm humans.
Using electron microscopy, the team found that a single plastic teabag at brewing temperature released about 11.6 billion micro-plastic and 3.1 billion nano-plastic particles into the water.
Scientists have previously detected microplastics in the environment, tap and bottled waters and some foods. Micro- and nano-plastic materials measured in food products are generally from accidental contamination, Tufenkji notes, but in this instance "you're literally adding plastic into the beverage."
Pyramid bags made of polyethylene are used to make cold brew coffee, tea, herbal infusions and to hold spices in cooking. Most tea and coffee filter materials are made from abaca, a natural fiber grown in the Philippines and Ecuador. Traditionally, these bags are sealed with plastic – either polypropylene or polyethylene. The plastic fibers form part of the paper and are bound (fused) within it.
The lead author of the study, Laura Hernandez, a Ph.D. student, says more research is needed to determine if the plastics could have more subtle or chronic effects on humans.
Learn more: mcgill.ca