Researchers estimate the weekly intake of plastic particles at up to five grams. This is roughly equivalent to the weight of a credit card. However, how plastic behaves in the body is still largely unknown. A group led by study leader Verena Pichler from the University of Vienna investigated the traces of micro- and nanoplastic particles (MNPs for short) in the body.

The researchers focussed on the gastrointestinal tract, where ingested plastic particles often end up. One of the key questions here is whether, how long and in what numbers they can potentially remain there and what consequences this has.

To this end, the scientists focused on four cell types that occur in colorectal tumours - a type of bowel cancer - in humans. The team then exposed these different cell lines to plastic particles of various sizes.

Tumour cells can migrate more easily

Their research has now shown that MNPs, like other waste products in the body, are absorbed by tiny "organs" within the cells - the lysosomes. These so-called organelles are actually responsible for breaking down foreign bodies. However, they don't stand a chance with the microplastic particles.

The scientist and her colleagues have now described for the first time that the plastic can even be passed on to newly formed cells during cell division. In addition, the team found the first signs that tumour cells contaminated with plastic can migrate more easily in the body and thus virtually help in the formation of cancer offshoots (metastases).

Given the ubiquity of plastics in the environment and the persistent exposure of humans to even the smallest plastic particles, further studies are urgently needed to investigate long-term effects in particular, the researchers said.