Every person in the Netherlands has “forever chemicals” in their blood, according to the country’s first national study on the topic.

The study, published Thursday, indicates that having per- and polyfluoroalkyl substances (known as PFAS) in levels above safety thresholds does not automatically lead to illness.

“However, it does mean that PFAS can have an effect on the body. For example, the immune system may function less effectively. The effects depend on the amount of PFAS, the duration of exposure, and a person’s individual health condition,” reads the study, conducted by the Dutch National Institute for Public Health and the Environment, or RIVM.

Out of 28 types of PFAS analyzed, the study found that at least seven kinds are present in almost everyone tested. The levels of PFAS were the highest in the regions of Dordrecht and Western Scheldt, due to the nearby chemical plants.

RIVM tested 1,500 blood samples taken in 2016 and 2017. The institute said it will also publish a study based on blood samples taken this year, expected to be published in 2026.

Earlier this year, RIVM told the Dutch people to stop eating backyard-produced eggs (produced by privately owned chickens rather than bought from shops or markets) due to contamination from PFAS.

PFAS are a group of commonly used chemicals that have been linked to a range of health problems, including cancer. They are known as forever chemicals because they don’t break down naturally.

RIVM is an agency of the Dutch Ministry of Health, Welfare and Sport, which provides independent research and advice to the government.