Besides water, tea is the most consumed beverage in the world, enjoyed around the world in a myriad of varieties served both hot and cold, at meals, enjoyed alone or in social settings. It wasn’t until the early 20th century that the world would get accidentally introduced to tea bags, a convenient single-serve sachet of tea, initially made of gauze, then paper, tea bags are now also made of synthetic materials.

Newer styles of tea bags, pyramid-shaped and described as “silken” are often made out of PET or nylon, and they release microplastic particles during steeping, new research finds, adding this popular beverage to the list of sources of human-ingested plastic.

McGill University scientist Nathalie Tufenkji was inspired to study just how much plastic is released while brewing after getting served one of these tea bags at a cafe. The results, published in Environmental Science and Technology, found that 11.6 billion microplastics and 3.1 billion nanoplastics get released during the steeping process. The researchers did not look into the effects of the plastics on humans, but when water fleas swallowed the particles, their behavior changed, and the organisms became agitated.