Researchers in Canada claim some premium tea bags could be leaving billions of microscopic plastic particles in your cup.
A team from McGill University in Montreal say more research is now needed into the health effects of microplastics.
Most teabags are made from paper, but some premium brands have switched to using a type of plastic mesh.
A spokesperson for McGill University said: "The team also explored the effects of the released particles on small aquatic organisms called Daphnia magna, or water fleas, which are model organisms often used in environmental studies.
"The researchers treated water fleas with various doses of the micro and nanoplastics released from the teabags. Although the animals survived, they did show some anatomical and behavioral abnormalities."
PhD student Laura Hernandez, the first author of the study, added: "More research is needed to determine if the plastics could have more subtle or chronic effects on humans."