The water serving more than a third of the Dutch population contains more PFAS than what the health guidelines set by the National Institute for Public Health and the Environment (RIVM) allow. This was reported by Greenpeace on Tuesday, based on analysis of data from the country’s 10 drinking-water companies. In the western part of the country, the guideline is reportedly sometimes exceeded by over three times. Therefore, the organization states that it is launching a postcode check to see PFAS measurements for tap water in an area. “It’s bizarre that there’s poison in our tap water,” the group said.

Noord-Holland has the most urgent levels of contamination. Around Zaandam and IJmuiden, the PFAS in tap water guideline is exceeded by more than three times. By more than two times in Amsterdam and two and a half times around Alkmaar and Den Helder.

The ten munisipalites with the most PFAS in tap water are Zaanstad, Haarlem, Haarlemmermeer, Amsterdam, The Hague, Zoetermeer, Leiden, Rotterdam, Westland, and Dordrecht. Water companies are reportedly investing in newer treatment plants.

PFAS is the umbrella name for thousands of industrial chemicals, which are discharged into air or water. They are sometimes called “forever chemicals,” because they do not break down in the environment. According to Greenpeace, long-term exposure can increase the risk of several types of cancer, raise cholesterol, and weaken the immune system.

RIVM and the drinking water association Vewin again said that tap water drinkers should not rush to switch to plastic-bottled water. The best answer is for the chemical industry to stop producing and discharging so much PFAS, the organization said.