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Nitrate

DESIGNATIONS

CAS No.:
Registry name:
Nitrate
Chemical name: Nitrate
Synonyms, Trade names:
Chemical name (German):
Nitrat
Chemical name (French):
Nitrate
Appearance:
colourless (depending on cations) solids, easily soluble in water

ORIGIN AND USE

Usage:
Nitrates are used as fertilisers and in the food industry. Some 90% of all meat products are salted, i.e. nitrate is added to them in the form of potassium nitrate (saltpeter).

Origin/derivation:
Nitric acid salt. Nitrate is part of the nitrogen cycle in nature. 78% of the air is nitrogen. The mineralisation of nitrogen initially produces ammonia which is oxidised by nitrifying bacteria to form nitrite and then nitrate.

Toxicity

Characteristic effects:

Humans/mammals: Infants assimilating large doses of nitrates may suffer not only from nitrosamine formation (carcinogenic), but also from methaemoglobinaemia (cyanosis). The first stage is the transformation to nitrite caused by small amounts of gastric acid, then the nitrite enters the bloodstream where it oxidises the haemoglobin to form methaemoglobin which inhibits the transportation of oxygen. 60-80% methaemoglobin has a lethal effect due to internal suffocation. The symptoms are similar to those of carbon monoxide poisoning.

Plants: An increase in nitrate content results in more water being absorbed; at the same time there is a decrease in the number of valuable constituents such as vitamin C or iron.

ENVIRONMENTAL BEHAVIOUR

Water:
The elution of nitrate from the topsoil into the groundwater is influenced by numerous factors and often takes months or even years.

Soil:
Various processes are responsible for the translocation of nitrate ions in soil; they are absorbed by plants and microorganisms, they are nitrified, they can be reduced by microbes to form ammonium ions (NH4+) or they are eluted into the groundwater by seepage water. Nitrate elution is clearly dependent on the amount and the frequency of rainfall and thus on the seasons (most pronounced in low-vegetation period). A high humus content results in more organically bound nitrogen which is biologically degraded to nitrate.

Degradation, decomposition products:
Nitrate may be transformed into nitrite by microorganisms in the intestines. As nitrites may react with numerous amines to form nitrosamines - especially at low pH values (e.g. in the stomach) - they deserve special attention.

Food chain:
Vegetables are the main nitrite source to humans (more than 70%; HEINZE 1986). The natural nitrate content of meat is insignificant. Nitrate is found in meat and fish as a result of the methods used to preserve such products. 80% of the nitrite assimilated in humans is a consequence of its formation from nitrate.

ENVIRONMENTAL STANDARDS

Medium/acceptor Sector Country/organ. Status Value Cat. Remarks Source
Water: Drinkw CS

(L)

15 mg/l

    acc. B.U. INST., 1984
Drinkw CH

(L)

20 mg/l

    acc. B.U. INST., 1984
Drinkw D

L

50 mg/l

    acc. LAU-BW, 1989
Drinkw DDR

(L)

40 mg/l

    acc. B.U. INST., 1984
Drinkw DDR

(L)

20 mg/l

    acc. B.U. INST., 1984
Drinkw EC

G

25 mg/l

    acc. LAU-BW, 1989
Drinkw EC

G

50 mg/l

    acc. LAU-BW, 1989
Drinkw GB

(L)

90 mg/l

    acc. HEINZE, 1986
Drinkw SU

(L)

40 mg/l

    acc. HEINZE, 1986
Drinkw USA

(L)

45 mg/l

    acc. HEINZE, 1986
Drinkw WHO

G

44.3 mg/l

    acc. LAU-BW, 1989
Groundw NL

G

5.6 mg/l

    acc. LAU-BW, 1989
Surface D

G

25 g/m3

  Investigation acc. LAU-BW, 1989
Surface D

G

50 g/m3

  Rehabilitation acc. LAU-BW, 1989
Surface EC

G

25 g/m3

  1) A1 acc. LAU-BW, 1989
Surface EC

G

50 g/m3

  2) A2 acc. LAU-BW, 1989
Waste water CH

(L)

25 g/m3

  Quality goal acc. LAU-BW, 1989
Foodstuffs   CH

L

3000 mg/kg

  Lettuce acc. B.U. INST., 1984
  D

(L)

5 mg/(kg.d)

ADI As sodium nitrate 3) acc. Gro▀klaus, 1989
  D

(L)

5 mg/(kg.d)

ADI As potassium nitrate 3) acc. Gro▀klaus, 1989
  D

(L)

100 mg/(kg.d)

ADI As potassium nitrate 4) acc. Gro▀klaus, 1989
  NL

(L)

4,000 mg/kg

  Lettuce acc. B.U. INST., 1984
  WHO

G

3.65 mg/(kg.d)

ADI   acc. B.U. INST., 1984

Notes:

1) For drinking water treatment in each case: quality requirements to be satisfied by surface water used for drinking water supply in member countries: A1 = G for simple physical treatment and sterilisation
2) For drinking water treatment in each case: A1 simple physical treatment and sterilisation, A2 = normal physical and chemical treatment/sterilisation and A3 = physical and refined chemical treatment, oxidation, adsorption and sterilisation
3) In meat, fish, cheese
4) In raw sausage
The use of nitrate as an additive is banned in Norway, Sweden and former East Germany (HEINZE, 1986).

Comparison/reference values

Medium/origin Country Value Source
Lettuce D 1490 mg/kg acc. RSU, 1987
Spinach D 965 mg/kg acc. RSU, 1987
Tomatoes D 27 mg/kg acc. RSU, 1987
Milk D 1.35 mg/kg acc. RSU, 1987
Meat products D 77 mg/kg acc. RSU, 1987
Fresh vegetables D 720 mg/kg acc. RSU, 1987
Baby food D 81 mg/kg acc. RSU, 1987

Assessment/comments

Uncontrolled usage of nitrate must be avoided because of its transformation in the human body to form nitrite and carcinogenic nitro-soamines which may be fatal to infants. The use of nitrates (smoking) to preserve foodstuffs should definitely be restricted.

In agriculture, nitrate fertilisers must not be applied in zones of drinking water catchment areas as well as in areas where nitrates can easily infiltrate into the groundwater (hydromorphous soils).


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