Researchers from McGill University have discovered doses of plastic in teas packaged in plastic tea bags, and they say that any possible health effects that could result from ingesting such plastics should be investigated further.

Knowing that all plastic breaks down into microplastics - and nanoplastics, which are even smaller - and that researchers have previously found microplastics in some water and foods, a team lead by McGill chemical engineering professor Nathalie Tufenkj decided to investigate if micro- and nano-plastics would be released during the brewing of tea packaged in plastic bags.

The McGill team purchased four types of commercially available teas that are packaged in such plastic bags. They then opened the bags and removed the tea leaves - so they wouldn't interfere with their testing - and brewed the emptied bags in water. They then used a process called electron microscopy to analyze the contents. What they found was that a plastic teabag at brewing temperature released 11.6 billion microplastic particles and 3.1 billion nanoplastic particles into the water.

The researchers say these levels are thousands of times higher than has previously been found in other foods. Laura Hernandez, a PhD student who is the lead author of the study, said more research is needed to determine the effects on humans of consuming such plastics. (The team's research on small organisms called water fleas who were treated with doses of the plastics released from the tea bags found some "anatomical and behavioural abnormalities").

Their research has been published in the American Chemical Society journal Environmental Science & Technology.