Some manufacturers sell tea in plastic bags rather than loose or in paper bags.

A couple of years ago, Nathalie Tufenkji stopped by a Montreal cafe on her way to work and ordered a cup of tea. She sat down with her mug, enjoying its warmth, before she noticed something strange: Her tea bag appeared to be made of plastic.

"I thought, 'That's not a very good idea, putting plastic into boiling water,' " she told The Washington Post.

Tufenkji was worried that the plastic bags could leech particles into the beverage that she and her fellow customers were consuming, and as a professor of chemical engineering at McGill University, she was well-positioned to investigate. She dispatched her student Laura Hernandez to purchase some tea bags from stores in the area and bring them back to the lab.

It turns out Tufenkji's hunch was right. The bags were releasing plastic particles into the brewed tea. Billions and billions of them.

Hernandez, Tufenkji and their fellow 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, Tufenkji said, that the plastic was coming from the tea bags themselves, not the tea.

Though Tufenkji declined to name the brands they used for fear of singling out one company over others, she said that some frequent tea drinkers could be repeatedly dosing themselves with billions of particles of plastic as they drank the beverage day after day. Some of the particles, she noted, would be small enough to potentially infiltrate human cells.

Some manufacturers sell tea in plastic bags rather than loose or in paper bags, even as the public becomes increasingly aware of how plastic is clogging our bodies of water, as well as our actual human bodies. While the health implications of consuming plastic are unknown, people around the world are inadvertently eating quite a lot of it.

Earlier this year, a report by the World Wide Fund for Nature estimated that on average, a person might ingest 5 grams of plastic a week, the equivalent size of a credit card. Researchers at the University of Newcastle in Australia compiled dozens of studies on the presence of plastic in water, as well as in food such as shellfish and even beer. Studies are underway to establish how plastic consumption can impact human health, according to WWF's study.

While the McGill study did not explore the human health impacts of consuming this plastic, when some of the particles were given to water fleas, they began acting erratically and developed some deformities, Tufenkji said.

"We just wanted to make the public aware of this," she said. "We want consumers to know that this is made of plastic so they can have the choice about whether this is really what they want to purchase."