UK Legal Limit
0.5 mg/L
WHO Guideline
3 mg/L
EU Standard
0.5 mg/L
Primary Sources
Distribution pipes, agriculture
Nitrite in UK drinking water is regulated at 0.5 mg/L. The WHO guideline is 3 mg/L and the EU standard is 0.5 mg/L. Nitrite is more toxic than nitrate and can form within distribution pipes. It poses the greatest risk to infants under three months old.
Nitrite poses a particular risk to infants under three months old. It reacts with haemoglobin in the blood to form methaemoglobin, which cannot carry oxygen — a condition known as methaemoglobinaemia or 'blue baby syndrome'. In severe cases this can be fatal. In adults, chronic nitrite exposure has been linked to the formation of N-nitroso compounds in the stomach, which are associated with an increased risk of gastric and oesophageal cancer. The risk is higher when nitrite is combined with dietary amines.
Nitrite in UK drinking water can form within the distribution network itself, particularly in systems that use chloramine (combined chlorine) as a disinfectant — bacteria can convert the ammonia component into nitrite through nitrification. Agricultural runoff, sewage contamination, and the breakdown of organic nitrogen in source water also contribute. Nitrite levels tend to be higher at the extremities of distribution networks where water has a longer residence time.
| Jurisdiction | Limit / Guideline | Notes |
|---|---|---|
| UK (DWI) | 0.5 mg/L | Regulated under the Water Supply (Water Quality) Regulations 2016 |
| WHO | 3 mg/L | World Health Organization Guidelines for Drinking-water Quality |
| EU | 0.5 mg/L | EU Drinking Water Directive (2020/2184). The UK no longer automatically mirrors EU standards post-Brexit. |
Reverse osmosis
A membrane filtration process that removes up to 99% of contaminants by forcing water through a semi-permeable membrane under pressure. Highly effective but produces some wastewater.
Ion exchange
Replaces unwanted ions (such as nitrate or lead) with harmless ones using resin beads. Effective and widely used in both whole-house and point-of-use systems.
Distillation
Water is boiled and the steam condensed, leaving most contaminants behind. Highly effective but slow and energy-intensive — typically used in countertop units.
No filter we list names nitrite specifically. Reverse osmosis is shown because it rejects dissolved contaminants broadly rather than by name. Check your own report before buying.
Waterdrop G3P600 Reverse Osmosis
Reverse Osmosis · NSF/ANSI 58, NSF/ANSI 372
Typical price
£550approx.
Affiliate link: we may earn a commission at no extra cost to you.
Waterdrop 10UA Under Sink
Under-Sink Filter · NSF/ANSI 42
Typical price
£75approx.
Affiliate link: we may earn a commission at no extra cost to you.
Want to know the Nitrite levels in your water? Enter your postcode to get a free report for your area.