Quirks and Quarks

New plastic tea bags shed billions of tiny particles into the cup

Canadian researchers find hot water and plastic tea bags are not an ideal combination

Canadian researchers find hot water and plastic tea bags are not an ideal combination

One of the plastic tea bags purchased by researcher Laura Hernandez to investigate whether or not they shed microplastic particles (Laura M Hernandez)

Not long ago Nathalie Tufenkji, a professor of Chemical Engineering at McGill University in Montreal, was surprised to discover that the tea she'd been served in a local shop came in a plastic tea bag.

The bag was made of a fine synthetic fabric, soft and silky in texture.  Tufenkji, whose done research previously on microplastics, was curious about whether the combination of this plastic bag and hot water would cause the plastic to shed microplastic particles into the cup.

She had her student Laura Hernandez shop to find an assortment of these bags, which seem to be relatively new to the market, and then tested them in her lab.

They were alarmed to discover that the bags did indeed shed large amounts of microplastic and nanoplastic particles — billions of them, in fact.

Tufenkji and her colleagues don't know precisely why the tea bags are shedding so much plastic. The fabric has a large surface area, and the hot water is certainly contributing to the issue, but the precise mechanism hasn't been observed yet.

As part of their recently published study they did preliminary toxicity testing on water fleas, which did show some impacts on the animals' behaviour, but it's difficult to extrapolate from that to any human health risks.

Tufenkji says, however, that even beyond any potential health risks, she'd avoid using the bags as they're just one more form of single use plastic that's probably unnecessary.

McGill researcher Laura Hernandez with one of the plastic tea bags she and her colleagues tested to see if they shed microplastic particles (Shawn Chahal)