Introduction. The presence of nitrates in water is the consequence of the use of mineral fertilisers in agriculture, sewage draining to waters, but also natural nitrification processes. Nitrates (NO3-) are not dangerous to people, however they can transform into much worse nitrites (NO2-) in acid environment. Nitrites are precursors of carcinogenic nitrosamines. Nitrates are especially dangerous for young infants because they cause methaemoglobinaemia, and in adults indirectly lead to an increase in the incidence of stomach and intestines cancer.

Aim. The aim of this work was to assess a daily intake of nitrates (V) and (III) with drinking water.

Material and method. The material consisted of bottled water at different levels of mineralisation, surface waters (water supplies) and ground water (local wells). The content of nitrates (V) and nitrates (III) was assessed using Visocolor® tests and PF 11 photometer.

Results. Concentration of NO3- ions in mineral and surface waters varied and was far below the limits stated in regulations. The content of nitrates (III) was very low in all three water sources and it was within detection limits of measures used in the study. Local wells had the worst characteristics as far as the studied indices were concerned.

Daily intake of nitrates (V) and (III) in drinking water was about 10 and 0.8% of the acceptable daily intake, respectively. For water of worse quality (wells) this index may rise to about 26 and 1.2, respectively. The presence of nitrates in drinking water (with the exception of well water) does not pose a threat to an adult. Vegetables from overfertilised fields or meat products preserved with nitrates are more abundant sources of these compounds in our diet.