Half of Spain may be drinking unsafe tap water under new scientific limits

More than 3,000 municipalities in Spain are currently providing tap water that exceeds a new health-based “precautionary limit” of 6 mg/l for nitrates, according to the latest analysis of government data. While 99% of Spanish water remains legally compliant under the older 50 mg/l EU standard, recent 2026 scientific studies link long-term exposure to levels above 6 mg/l to increased health risks for infants and pregnant women. 

Regions with intensive farming, such as Castilla-La Mancha, Murcia, and Aragon, are the most affected, with some rural aquifers showing levels five times higher than the new recommended threshold. For residents and expats, the immediate consequence is a recommendation to check local SINAC reports and consider filtration systems for vulnerable groups until national safety standards are officially updated.

How the study measured water safety

The analysis uses publicly available data from SINAC, Spain’s national database that collects water quality readings from thousands of supply points across the country. Instead of focusing only on legal breaches, researchers applied a more conservative benchmark based on recent scientific studies linking long-term nitrate exposure to potential health risks.

This approach shifts the question from “is the water legal?” to “is it optimal for long-term health?” Under this stricter threshold, a large number of municipalities that currently meet legal standards would still fall into a higher-risk category.

Which areas are most affected

Higher nitrate concentrations are most commonly found in regions with intensive agriculture and livestock farming. The report points to areas in:

• Castilla-La Mancha
• Murcia
• Comunidad Valenciana
• Aragón
• Parts of Catalonia

These regions rely heavily on groundwater, which is more vulnerable to contamination from fertilisers and animal waste seeping into aquifers. In contrast, large urban centres that depend more on mixed or treated water sources tend to show lower concentrations, although they are not completely unaffected.

Environmental groups including Greenpeace have warned that nitrate contamination is widespread across Spain and continues to worsen in some regions.

Why scientists are concerned about lower limits

While the legal threshold of 50 mg/l remains in place, newer research suggests that health effects may occur at much lower levels, particularly with long-term exposure. Nitrates themselves are not directly toxic in small quantities, but they can convert into nitrites in the body, which have been linked to health risks in infants and potentially other long-term conditions. This is why some researchers and environmental groups are pushing for stricter standards and more preventive monitoring.

What this means for residents and expats

For most people in Spain, tap water is still considered safe under current regulations. However, this analysis may explain why many residents already choose bottled or filtered water in certain areas.

For expats and frequent travellers, the main takeaway is that water quality can vary significantly depending on location, especially in rural or agricultural zones. Those living in higher-risk regions may consider checking local water reports or using filtration systems as a precaution, particularly for infants or vulnerable groups.

What expats often ask about tap water consumption

Can you check nitrate levels in your area?
Yes. Data is available through SINAC, where users can search by municipality to see local water quality readings.

Who should be more cautious about nitrate levels?
Infants under six months and pregnant women are generally considered more sensitive to nitrate exposure. In higher-risk areas, additional precautions such as filtered or bottled water may be recommended.

Will Spain change its water safety limits?

There is currently no confirmed timeline for lowering nitrate limits in Spain or across the EU. However, increasing scientific evidence and environmental pressure could push authorities to review existing standards in the coming years.

At the same time, reducing nitrate pollution at source, particularly from agriculture, remains one of the biggest long-term challenges.