What should and should not be in water: WHO, EU and Thai limits

In short: good water contains calcium, magnesium, bicarbonates and a little sodium, and how much of each depends on the source. Everything beyond that is capped by regulation. Arsenic and lead are limited to 0.01 mg/L, nitrate to 45-50 mg/L, and fluoride in bottled water in Thailand to 0.7 mg/L. Mineral waters follow separate rules, so you cannot judge them and tap water by the same table.

Which minerals should water contain?

Water with no minerals is distilled water, and it tastes flat. A normal composition rests on six ions, and their sum is the mineralisation: 62 mg/L in Icelandic Glacial according to the brand, up to 500 mg/L for water in 18.9 L bottles under the Thai standard, and 7-10 g/L in Essentuki No. 4. Limits on the minerals themselves exist for the sake of taste, not safety: Russian rules cap chloride at 350 mg/L and sulphate at 500 mg/L, while the WHO sets no limit for them at all.

• Six ions make up the bulk of the composition: calcium, magnesium, sodium with potassium, bicarbonates, sulphates and chlorides
• Their sum is the mineralisation. Icelandic Glacial has 62 mg/L according to the brand, Narzan 2-3.5 g/L, and Essentuki No. 4 as much as 7-10 g/L
• These ions are not harmful in themselves. The limits on them are mostly about taste: the Russian SanPiN rules allow no more than 350 mg/L of chloride and no more than 500 mg/L of sulphate in drinking water
• The WHO sets no limit at all for sulphate or total mineralisation: in ordinary amounts they are not dangerous, they only change the taste

Nitrate and nitrite

These two lines say nothing about taste; they tell you how clean the source is, because nitrate arrives from fields and run-off rather than from the rock. The limits are close to one another almost everywhere: 50 mg/L for the WHO, the EU and Thailand, and 45 mg/L in the Russian SanPiN, and in protected groundwater the figures are usually several times lower. Nitrite varies more: 3 mg/L for the WHO, the SanPiN and Thailand, against 0.5 mg/L for EU tap water and 0.1 mg/L for natural mineral water.

• Nitrate reaches water with fertilisers and run-off, which is why it is the first thing tested
• The WHO, EU Directive 2020/2184 and the Thai standard for bottled water all set 50 mg/L. The Russian SanPiN 1.2.3685-21 is stricter, at 45 mg/L
• Nitrite: the WHO, Thailand and the SanPiN allow up to 3 mg/L. In the EU the limit is 0.5 mg/L for tap water and 0.1 mg/L for natural mineral water
• Good groundwater usually sits far below the nitrate limit. A label figure close to 45-50 is a reason to pick a different water

How much fluoride and arsenic is allowed in water?

These four substances are tested in every batch, and their limits are the tightest of all. Arsenic and lead are capped at 0.01 mg/L almost everywhere, and from 12 January 2036 the EU halves lead to 0.005 mg/L. The general fluoride limit is 1.5 mg/L, but hot climates bring it down: Thailand sets 0.7 mg/L for bottled water, and the Russian rules set the same 0.7 mg/L for the hottest climate zone, where people drink more. Boron is the one line where the limits differ fivefold, from 0.5 mg/L in the SanPiN to 2.4 mg/L at the WHO.

• Fluoride: the WHO, the EU and the SanPiN allow up to 1.5 mg/L. Thailand sets 0.7 mg/L for bottled water, and the Russian rules also set 0.7 mg/L for the hottest climate zone, because people drink more in the heat
• Arsenic and lead: the limit is 0.01 mg/L almost everywhere. From 12 January 2036 the EU brings lead down to 0.005 mg/L
• Boron: the WHO and Thailand allow 2.4 mg/L, the EU 1.5 mg/L and the SanPiN 0.5 mg/L. The gap is wide because experts assess the safe dose differently
• Uranium: the WHO, the EU and Thailand allow up to 0.03 mg/L. The SanPiN is twice as strict, with a limit of 0.015 mg/L

Why mineral water has rules of its own

You cannot judge mineral water and tap water by the same table. Mineral water is drawn from deep protected wells and is not stripped down to nothing: its natural composition is exactly what people buy it for. That is why the EU gives it a separate set of rules, Directive 2003/40, which allows up to 5 mg/L of fluoride but only 0.1 mg/L of nitrite. Above 1.5 mg/L of fluoride the label has to say so, because that water is not given regularly to children under 7. Thailand's Notification No. 462 does not cover natural mineral waters either.

• Mineral water is drawn from deep protected wells and is not purified down to zero; its natural composition is exactly what people value
• In the EU, natural mineral waters follow Directive 2003/40: fluoride up to 5 mg/L, nitrate up to 50 mg/L, nitrite up to 0.1 mg/L and arsenic up to 0.01 mg/L
• Above 1.5 mg/L of fluoride, EU labels must state that the water should not be given regularly to children under 7
• The Thai standard for bottled water (Ministry of Public Health Notification No. 462 of 2025) does not apply to natural mineral waters: they have a notification of their own

How to check your own water

Three steps that take a minute at the shelf. First, the water type and the mineralisation: together they tell you straight away whether this is table water or medicinal-table water. Second, the ion table in mg/L, which you will find both on Narzan and on the Thai sticker of Essentuki No. 4. Third, the Thai FDA registration number, without which the water is best left where it is. Nitrate, fluoride and arsenic are usually missing from that table: the full batch analysis is something you ask the seller for, and an importer holds one for every shipment.

• Check the label for the water type, the mineralisation and the main ions. Narzan and Essentuki No. 4 list each ion in mg/L
• Water in 18.9 L bottles on Phuket follows the Thai standard: total mineralisation no higher than 500 mg/L and hardness no higher than 100 mg/L as calcium carbonate
• A Thai FDA registration number on the label means the producer has passed inspection. Without it, leave the water on the shelf
• All of this is general standards and manufacturer data, not medical advice

Sources

• WHO: Guidelines for Drinking-water Quality, 4th edition (2022)
• SanPiN 1.2.3685-21: drinking water parameters, tables 3.5 and 3.13
• Directive (EU) 2020/2184 on the quality of water intended for human consumption
• Directive 2003/40/EC: limits for natural mineral waters
• Thai Ministry of Public Health Notification No. 462 (2025) on drinking water in sealed containers
• GOST R 54316-2020, Natural mineral drinking waters