Nitrates neturaly occur as part of nitrogen cycles. Ion nitrates represents overall product of nitrogen compounds oxidation and its presence in waters signifies on old pollution or on old source of pollution.
Origin in water
Presence of this ion in underground waters signifies on complete oxidation compounds which comprehend nitrogen. Nitrates sources are mineral deposits (sodium and potassium nitrate), soils, seawater and atmosphere. Nitrates partly find in soil and from that they are outspread in environment from food to atmosphere and water. Larger concentrations expect on the territory where son use, during decay of animal and plant putrefaction, in waters from disposition of mud, garbage and industrial waste. Nitrates are always in bigger concentration then nitrites. Higher level of nitrates is finding in underground waters, even to 20 mg/1, but the highest concentrations are in shallow aquifers, polluted settlement and/or with excess sons use. In surface waters, nitrates operations like sons from plants strive to reduce nitrates concentration, but leave the underground waters problem.
Some epidemiologic studies, which practised from USEPA in 1990, try to value possible connection between nitrates in water and cancer. USEPA concludes that these studies are not enough to show increment of cancer risk.
Water usage with nitrates concentration from 10 mg/l procure methaemoglobinemia.
Maximal allowable concentrations
According to recommendations of EU (Directive 98/83/EC) limitary value for nitrates is 50 mg/l. The same value is in our rules for drinking water (Sl. list SRJ 42/98).