The level of cancer-causing PFAS chemicals in eggs from hens kept as a hobby is so high that people should stop eating them, public health institute RIVM said on Thursday following an investigation in 31 locations in Zuid-Holland.

The agency, which warned earlier about the risk to eggs from PFAS, is now carrying out nationwide research into eggs from hens kept in back gardens and city zoos to establish the full extent of the problem.

The RIVM looked at eggs from 31 places close to the Chemours factory in Dordrecht, which is the subject of several court cases because of its role in PFAS pollution.

In most of the eggs examined, the volume of PFAS was so high that eating just one egg would be equivalent to the maximum exposure recommended by health experts in a week.

The agency points out that the PFAS consumed via eggs comes on top of the other sources of the contaminant, including other food and water. “If people consume more PFAS over time than recommended, they will damage their health,” the RIVM said.

In February, the European Pesticide Action Network said the Netherlands and Belgium are more likely than all 25 other EU member states to produce fruit and vegetables that contain PFAS pesticide residues.

The EU plans to stop the use of the harmful PFAS in many industries but not their inclusion in pesticides because these fall under separate EU regulations.

Two years ago the Dutch public health institute RIVM warned people who go fishing as a hobby to sharply reduce their consumption of fish, shrimp, oysters and mussels caught in the Westerschelde estuary because of chemical pollution.

Fish and shellfish caught in the estuary can contain eight to 10 times the amount of PFAS found in similar products sold in the shops, the RIVM said at the time.