By Kenny Stancil

A team of toxicologists found microplastics in nearly 80% of the healthy adult blood samples it analyzed, marking the first time that tiny polymer fragments—measuring less than 5mm in size—have been detected in human blood, The Guardian reported Thursday.

Using techniques that allowed them to detect particles as small as 0.0007mm, the scientists, whose research was published in the peer-reviewed journal Environment International, examined blood samples provided by 22 anonymous donors in good health and discovered microplastics in 17 of them.

According to The Guardian, “Half the samples contained PET plastic, which is commonly used in drinks bottles, while a third contained polystyrene, used for packaging food and other products. A quarter of the blood samples contained polyethylene, from which plastic carrier bags are made.”.