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.

By Ian Horswill


Posted on September 27, 2019

The finer tea comes in ‘silken’ bags to differentiate itself from traditional paper tea bags and it has a price to match. Some silken tea bags are pyramid-shaped and marketed as if to make room for the large leaves in premium tea leaves to expand.

McGill University in Montreal, Canada, carried out a study that estimates one cup from a single tea bag could contain 11.6 billion microplastic and 3.1 billion nanoplastic particles, in the journal Environmental Science & Technology.

Nathalie Tufenkji, a professor of chemical engineering at the university, saw a plastic tea bag in the drink she ordered from a coffee shop one morning.

“I said, ‘Oh God, I’m sure if it’s plastic it’s, like, breaking down into the tea,'” she told CBC News.

When she returned to work she asked her graduate student, Laura Hernandez, to buy a selection of the tea bags from different brands and to test them.

When put under hot water the bags released microplastic and even smaller nanoplastic particles. Tufenkji had been expecting hundreds of particles of microplastic.

“We were shocked when we saw billions of particles in a single cup of tea,” she said.

The amount of microplastic and nanoplastic in a plastic tea bag is much higher than that found in bottled water, beer, honey, fish and shellfish, chicken or salt.

Tufekji said the higher amount was simply because her study included and counted smaller particles than most other studies. It’s also because, for most foods and beverages, the plastic is an accidental contaminant.

With a hot plastic tea bag “you’re literally adding plastic into the beverage.”

The Tea and Herbal Association of Canada told CBC News in a statement that the materials used in the bags in the study, PET (polyethylene terephthalate, found in plastic drink bottles) and nylon (used in many food bags and pouches), have been deemed safe for use in contact with hot food and beverages. It added there is no evidence the microparticles pose a risk to human health.

The World Health Organization (WHO) last month called for a further assessment of microplastics in the environment and their potential impacts on human health, following the release of an analysis of current research related to microplastics in drinking water.

“Based on the limited information we have, microplastics in drinking water don’t appear to pose a health risk at current levels. But we need to find out more. We also need to stop the rise in plastic pollution worldwide,” said Dr Maria Neira, the Director at the Department of Public Health, Environment and Social Determinants of Health, at WHO.