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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. Großklaus, 1989 | ||
| D | (L) |
5 mg/(kg.d) |
ADI | As potassium nitrate 3) | acc. Großklaus, 1989 | ||
| D | (L) |
100 mg/(kg.d) |
ADI | As potassium nitrate 4) | acc. Großklaus, 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).