Microplastics cause damage to human cells in the laboratory at the levels known to be eaten by people via their food, a study has found.

The harm included cell death and allergic reactions and the research is the first to show this happens at levels relevant to human exposure. However, the health impact to the human body is uncertain because it is not known how long microplastics remain in the body before being excreted.

Microplastics pollution has contaminated the entire planet, from the summit of Mount Everest to the deepest oceans. People were already known to consume the tiny particles via food and water as well as breathing them in.

The research analysed 17 previous studies which looked at the toxicological impacts of microplastics on human cell lines. The scientists compared the level of microplastics at which damage was caused to the cells with the levels consumed by people through contaminated drinking water, seafood and table salt.

They found specific types of harm – cell death, allergic response, and damage to cell walls – were caused by the levels of microplastics that people ingest.

“Harmful effects on cells are in many cases the initiating event for health effects,” said Evangelos Danopoulos, of Hull York Medical School, UK, and who led the research published in the Journal of Hazardous Materials. “We should be concerned. Right now, there isn’t really a way to protect ourselves.”

Read more about the study here and see the study itself here.