Plastic tea bags found to release millions of microscopic plastic particles into a brew - study

Cup of tea
Tea, water, milk, sugar - and plastic? Photo credit: File

There's nothing quite like a cup of tea with a side of biscuits - but how about a side of plastic particles?

New research suggests that millions of microscopic plastic particles are released from tea bags, meaning that afternoon brew is likely contaminated by chemicals.

While it's easy to assume that tea bags are made from pure paper, an estimated 96 percent of the bags contain polypropylene - a thermoplastic polymer. This chemical acts as a seal on the tea bags, ensuring they maintain their shape. 

Although a number of brands, particularly in the tea-loving UK, have made an effort to remove polypropylene from their products, a high quantity of tea brands worldwide may still contain plastic. 

As reported in the Environmental Science & Technology journal, McGill University researchers have investigated whether plastic tea bags could be releasing micro and nano plastics during brewing. It is currently unknown if these particles are harmful to humans.

The plastic tea bags used in the experiment were emptied and washed before being heated, to imitate brewing conditions.

"All experiments were conducted with cut and emptied tea bags to ensure that the enumerated particles originated from the tea bag material and not the tea," says the study.

The researchers found a single plastic tea bag at brewing temperature (95 degrees celsius) released approximately 11.6 billion microplastics and 3.1 billion nano plastics into a single cup.

"The levels of nylon and polyethylene terephthalate particles released from the tea bag packaging are several orders of magnitude higher than plastic loads previously reported in other foods," says the study.

The team also studied the effects of the particles on aquatic organisms, 'Daphnia Magna', otherwise known as water fleas. Although the organisms survived, the researchers noted some "behavioural and developmental" abnormalities.

"An initial acute invertebrate toxicity assessment has demonstrated that exposure to the particles released from tea bags could cause "dose-dependent behavioural and developmental effects," says the study.

A number of tea brands available in New Zealand have moved towards plastic-free products. Dilmah's organic range of tea bags are free of plastic, and Red Seal tea bags are bleach and chemical-free.