Tiny plastic particles have been discovered in human waste for the first time, according to research that the Medical University of Vienna and Austria's Federal Environment Agency presented on Tuesday.

In their pilot study, the scientists asked eight adults in Austria, Britain, Finland, Italy, the Netherlands, Poland, Russia and Japan to keep a diary of what they ate over the course of a week, and to provide a stool sample.

All of the test subjects ate food that was packaged in plastic or drank from plastic bottles. None of them were vegetarians.

The eight of them all had plastic in their waste.

"In our laboratory, we were able to detect nine different types of plastics ranging in size from 50 to 500 micrometres," said Bettina Liebmann, a researcher at the Environment Agency.

Other previous studies on animals have revealed microplastics in the digestive system, as well as in blood, lymph fluid and in the liver.

Although there are initial indications that digestive organs can be damaged by plastic chemicals or by inflammation that is caused by particles, further studies are needed to assess the risk for humans, the scientists said.

The research team was also not able to link the detected particles and the types of food that were eaten by the testers.

Microplastics include rubber abrasion from car tyres, construction rubble and cosmetics ingredients.

Germany's Federal Institute for Risk Assessment said on Tuesday it is unlikely that microplastics intake is a health risk for humans, according to the current state of research.