Substance fact sheet
The National Pollutant Inventory (NPI) provides information on the types and amounts of pollutants being emitted in the Australian community.
This page provides facts about total nitrogen. It describes how you might be exposed to this substance, how exposure might effect you and the environment, common uses, comparative data about total nitrogen and its physical and chemical properties.
For more information about some of the terms used in this page, see the NPI glossary.
The National Pollutant Inventory (NPI) holds data for all sources of total nitrogen emissions in Australia.
There are no specific health effects directly associated with total nitrogen as such - nitrogen is in fact an essential nutrient for life and integral constituent of protein.
The main health effects associated with nitrate and nitrite is methaemoglobinaemia (often referred to as 'blue-baby syndrome'). Infants and pregnant mothers are particularly susceptible to this condition. Nitrite oxidises haemoglobin to methaemoglobin a form which is unable to transport oxygen to body tissue. Although nitrite is the direct cause of methaemoglobinaemia, the toxicity of nitrate is the result of its reduction to nitrite within the body after ingestion.
Although nitrate and nitrite have not been demonstrated to be carcinogenic, nitrite does react with some compounds in the human stomach to form 'N-nitroso' compounds. Most N-nitroso compounds have been found to be carcinogenic to all animal species tested and consequently are also likely to be carcinogenic to humans. Data from a number of epidemiological studies have nevertheless only been suggestive in relation to this issue. Some geographical correlation studies have also suggested associations between nitrate levels in water supplies and some forms of gastric cancer, however, follow up studies have been equivocal. This could be the result of the intake of dietary components of vegetables, such as vitamins C and E, which decrease the risk of gastric cancer, may well mask or antagonise the effects of high nitrate intake in such correlation studies.
A more general concern in relation to the inorganic component of Total Nitrogen is its environmental effects, where elevated levels of nitrogen (and phosphorus) often cause enhanced algal growth. This may ultimately manifest itself as cyanobacterial (blue-green algal) blooms which can produce hepatotoxins, neurotoxins and endotoxins and affect human health through contact or consumption.
The main pathway of nitrate into the human body is through eating, where nitrate levels in drinking water are below 10 mg-nitrate/L (0.01 g-nitrate/L). Where nitrate levels in drinking water exceed 50 mg-nitrate/L (0.05 g-nitrate/L) drinking becomes the main pathway. Nitrite is usually found at low levels in water supplies, consequently food, particularly cured meats, provides the dominant source for the human body. Inhalation of oxidised forms of nitrogen as a result of air pollution is only a minor source. Note of course that nitrogen gas (N2) represents about 80% of the air we breath, although it is unreactive.
Through eating food containing nitrates and/or nitrites, or by drinking water containing nitrates and/or nitrites in solution.
See Sources for more information.
NHMRC & ARMCANZ 1996 Australian Drinking Water Guidelines
nitrate:50 mg-nitrate/L (i.e. 0.05 g/L). Levels of up to 100 mg-nitrate/L (i.e. 0.1 g/L) can be safely consumed by adults and children over 3 months of age. Where a water supply has between 50-100 mg-nitrate/L (i.e. 0.05 to 0.1 g/L) alternative water sources are needed for bottle-fed infants under 3 months of age. Although nitrite levels are generally not high in natural waters a standard of 3 mg-nitrite/L (i.e. 0.003 g/L) has been set. (NHMRC and ARMCANZ , 1996). In major Australian water supplies nitrate concentrations may range up to 18 mg-nitrate/L, (0.018 g/L) but is typically less than 0.15 mg-nitrate/L (0.00015 g/L). High concentrations of nitrate have been recorded in some groundwaters. Nitrite is generally not present in significant levels.
The Australian NOHSC National Exposure Standards Database link is probably the most useful source of information.
High concentration of total nitrogen are, in conjunction with other factors, often associated with algal blooms (including toxic blue-green algal blooms), as well as dense aquatic plant growth. This process of high nutrient input and algal growth is known as eutrophication, which can lead water which does not support aquatic life.
Most total nitrogen is transported by fluvial processes such as runoff and streamflow, although aeolian processes (wind) may at times also transport components of total nitrogen around the landscape. See also Sources (above) for human mediated transport mechanisms of total nitrogen.
In rivers and lakes the inorganic components of total nitrogen (ammonia, nitrate and nitrite) will become available for algal growth. High total nitrogen levels together with high phosphorus levels and in conjunction with favourable physical characteristics of aquatic environments this may result in algal blooms. After assimilation in algal (plant) growth, microbial breakdown and other processes such as mineralisation and nitrification may transform organic nitrogen through various steps into inorganic forms of nitrogen such as ammonia, nitrite and nitrate. As a generalisation, however, natural surface waters may contain significant amounts of organic-nitrogen and nitrate, but generally little ammonia or nitrite. Two other important microbiologically mediated processes influence total nitrogen levels in water - denitrification and nitrification. Denitrification results in the breakdown of nitrate-nitrogen by bacteria into nitrogen gas, which may remain dissolved in the water or be lost to the atmosphere. In either case the molecular nitrogen is no longer available for biological activity. Conversely some blue-green algae (cyanobacteria) can, under certain conditions, convert gaseous nitrogen dissolved in water into nitrate. This process is called nitrogen fixation or nitrification. These same types of cyanobacteria assist legumes to 'fix' atmospheric nitrogen in the case of terrestrial plants.
Because various factors, such as flow, light, turbidity, temperature, phosphorus levels, zooplankton grazing etc., can limit algal growth, it is not possible to recommend absolute total nitrogen concentration for aquatic environments that will prevent algal blooms. Nevertheless the following environmental guidelines have been set for total nitrogen (ANZECC, 1992).
Rivers and steams
100-750 micrograms/L (0.0001 to 0.00075 g/L) (as total-nitrogen)
Lakes and reservoirs
100-500 micrograms /L (0.0001 to 0.0005 g/L) (as total-nitrogen)
Estuaries and embayments
10-100 micrograms /L (0.00001 to 0.0001 g/L) (as nitrate-nitrogen)
Coastal waters
10-60 micrograms /L (0.00001 to 0.00006 g/L) (as nitrate-nitrogen).
In recognition that other factors can have a major influence on the effects of nutrient levels, the future ANZECC guidelines will adopt a risk-based approach. This will involve the use of a decision-tree with guideline levels for nitrogen (and phosphorus) largely determined by these other influencing factors.
Note that the emissions data in the NPI database is not directly comparable with these guidelines.
Not applicable for total nitrogen as it is not a product as such. Nevertheless, the major use for nitrate is inorganic fertiliser. It is also used as an oxidising agent in the production of explosives, while purified potassium nitrate is used for glass making. Sodium nitrite is used as a food preservative especially in cured meats. Sodium nitrate is often also added with such food preservatives to provide a reservoir for nitrite.
Emissions to surface water or groundwater from food processing industries, Sewage treatment plants, Leachate from garbage tips, Intensive livestock industries for example: feedlots, large poultry operations.
Catchment runoff - The organic-nitrogen components of total nitrogen are typically derived from soil, plant and animal material associated with agricultural land uses.
Fertilisers (e.g. ammonium nitrate) and manures.
Urban runoff, e.g. home fertiliser use.
The organic-nitrogen components of total nitrogen are typically derived from soil, plant and animal material.
Exhaust emissions from automobile use contain oxides of nitrogen which will be dissolved by rain, and thereby enter streams, lakes, and other water bodies.
Most food products contain nitrogen in various organic and inorganic forms. Many vegetables and fruits, such as spinach, beetroot, lettuce radish and rhubarb contain relatively high levels of nitrate. While meat, fish and dairy products contain significant amounts of organic-nitrogen as proteins, they generally contain lower amounts of nitrate and nitrite than fruits or vegetables. Cured meats and sausages which are commonly preserved with sodium nitrite and nitrate, are another significant source of nitrate and nitrite in most diets. Lawn and garden fertilisers contain nitrates. Furniture- and floor-polish, and household cleaners may contain nitrites. Water may also be a significant contributor to the intake of nitrate-nitrogen, particularly where the supply is derived from groundwater or polluted surface water.
Approximately 400 substances were considered for inclusion on the NPI reporting list. A ranking and total hazard score was given based on health and environmental hazards and human and environmental exposure to the substance.
Total nitrogen was ranked as 17 out of 400. The total hazard score taking into account both human health and environmental criteria is 3.8.
On a health hazard rating of 0 - 3 total nitrogen registers 0.8. A score of 3 represents a very high hazard to health, 2 represents a medium hazard and 1 is harmful to health.
On an environmental rating of 0 - 3 total nitrogen registers 3.0. A score of 3 represents a very high hazard to the environment and 0 a negligible hazard.
Factors taken into account to obtain this ranking and these scores include the extent of the material's toxic or poisonous nature and/or its lack of toxicity, and the measure of its ability to remain active in the environment and whether it accumulates in living organisms. It does not take into account exposure to the substance. Environmental exposure is reflected in the NPI rank for this substance (see comparative data below). A substance that scores highly as an environmental hazard is oxides of nitrogen at 3.0 and one of the lower scores is carbon monoxide at 0.8. A substance that scores highly as a health hazard is arsenic at 2.3 and one of the lowest scores is ammonia at 1.0.
| Substance name | Total nitrogen |
| CASR number | Not applicable |
| Molecular formula | The formula for the nitrate ion is NO3-. The formula for the nitrite ion is NO2-. |
| Synonyms | Total nitrogen is defined for the NPI as compounds that give rise to nitrate and nitrite ions. This is a very broad group including many natural and man made substances, either containing nitrates or nitrites or decomposing into either or both of them. |
| Physical properties: Salts: Nitrate: Nearly all nitrate salts are soluble in water. Nitrite: Nearly all nitrite salts are soluble in water. |
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| Chemical properties: Salts: Nitrate: Nearly all nitrate salts are dissociated at neutral pH. Nitrite: Forms salts with lithium, sodium, potassium, calcium, strontium, barium, silver. Reactivity: Nitrate: Generally chemically unreactive, although it can be reduced by microbial action. Nitrite: Relatively reactive. Chemical and biological processes can reduce nitrite to various compounds or oxidise it back to nitrate. Oxidises antioxidants, haemoglobin (to methaemoglobin), primary amines, nitrosates such as secondary and tertiary amines and amides. |
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There is more information that may be useful in understanding some of the issues surrounding the NPI.