Water purity varies across Europe, with Belgium, Germany, Luxembourg and the Czech Republic having some of the most polluted groundwater on the continent.
Groundwater is one of the most critically endangered resources across the EU.
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More than 20% across the bloc is in a poor chemical status, meaning that harmful substances, such as mercury, cadmium, and others, are above levels set by the EU Water Framework Directive, says the European Environment Agency.
Adding to the pressure is the enormous social and environmental cost of treating it for drinking and sanitation.
Just treating nitrates — often found in fertilisers — is thought to cost the EU as much as €320 billion per year.The EU's limit is 50 milligrams per litre, but according to the European Commission, that level was exceeded at 14% of Europe's groundwater measuring stations.
Who's got the healthiest tap water?
Europe's huge investments in groundwater sanitation do, however, seem to be effective.
Nineteen of the 20 countries with the best sanitation and drinking water in the world are European, with Japan being the only exception, according to the Environmental Performance Index.
Finland, Iceland, the Netherlands, Norway, Switzerland and the UK scored a perfect 100 points for protecting human health from unsafe drinking water and sanitation.
The worst rates in the continent emerged in Moldova (50 points), Georgia (51.7) and Albania (54.1), with three EU countries also in the lowest 10 spots in Europe: Latvia (59.10), Lithuania (58.40) and Romania (56).
In addition, existing legislation, the EU is keeping a close eye on its water resources.
In January 2022, it passed the first drinking water watchlist, with the aim of tracking beta-estradiol and nonylphenol levels — two endocrine-disrupting compounds which mimic, block, or interfere with the body’s hormones.
How concerning is groundwater pollution in the EU?
Nonetheless, groundwater chemicals remain a problem, particularly considering that groundwater supplies roughly 25% of agricultural irrigation and 65% of drinking water in the EU.
"Around 80% of all wastewater worldwide enters water bodies without undergoing treatment", say researchers at the Water Atlas, a groundwater purity index created by German think tank Heinrich Böll Foundation.
"The idea that rivers would clean themselves soon proved to be an illusion: rivers and lakes became stinking, toxic cesspools," they add.
The Water Atlas has mapped groundwater bodies with a good and bad chemical status in Europe, based on the EU's Water Directive standards.
The results in some countries are concerning.
In Luxembourg, 79% of mapped groundwater bodies failed to achieve a good chemical status in 2025, 55% in the Czech Republic, 41% in Belgium and 40% in Germany.
Pesticides remain one of the main threats to water quality. For example, trifluoroacetic acid (TFA) has been detected in 94% of 36 tap water samples collected in 11 EU countries, according to the Water Atlas.
Many pesticides also contain PFAS (per- and polyfluoroalkyl substances, also known as forever chemicals), which were detected at 23,000 locations across Europe.
Pharmaceutical compounds — with more than 175 identified in Europe's groundwater bodies — and microplastics pose additional environmental pressures.