I always thought that a teabag was completely biodegradable but it appears not!

Most teabags are made from paper, with a small amount of plastic used to seal them shut. But some premium brands have switched to using greater amounts of plastic mesh for their product instead.

This is usually so that the tea bag is held in a pyramid shape, which producers claim helps the tea leaves infuse better.

The researchers removed the tea and placed the empty teabags in water heated to 95C (203F), as if they were brewing tea.

They found that a single plastic teabag released about 11.6bn microplastic and 3.1bn smaller nanoplastic particles into the hot water. The particles are completely invisible to the naked eye.