Researchers at McGill University tested four kinds of plastic tea bags in boiling water, and found that a single bag would release more than 11 billion microplastic and 3 billion nanoplastic particles. You would not be able to see the contamination with your own eyes; the researchers had to use an electron microscope. But it’s there.

Their findings were published in the American Chemical Society journal Environmental Science & Technology this month. The four brands of tea they tested came from regular grocery stores in Montreal. After emptying and cleaning the tea bags of any trace of tea leaves, they submerged them in water heated to 203 degrees Fahrenheit, and then they left the bags to steep for five minutes.

The researchers then examined the water for leftover particles, placing drops on a slide and examining them under an electron microscope. There, they could see particles of varying sizes, some a little larger, some frighteningly small. Further testing of additional samples revealed their structures and confirmed that the material was made of the same plastic materials as PET, a kind of polyester, and nylon. It was clear, according to one of the researchers, that the plastic was coming from the tea bags themselves, not the tea.

https://pubs.acs.org/doi/10.1021/acs.est.9b02540

https://www.washingtonpost.com/climate-environment/2019/09/27/these-tea-bags-release-billions-plastic-particles-into-your-brew-study-shows/