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.
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.
Nitrate: Nearly all nitrate salts are soluble in water.
Nitrite: Nearly all nitrite salts are soluble in water.
Nitrate: Nearly all nitrate salts are dissociated at neutral pH.
Nitrite: Forms salts with lithium, sodium, potassium, calcium, strontium, barium, silver.
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.
The National Pollutant Inventory (NPI) holds data for all sources of Total Nitrogen 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.
Entering the body
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.
Workplace exposure standards
Safe Work Australia sets the workplace exposure standards for airborne contaminants. There are no workplace exposure standards for total nitrogen
Drinking water guidelines
The Australian Drinking Water Guidelines include the following guidelines for acceptable water quality:
- Maximum of 50 milligrams per litre of water for health purposes
- Maximum of 3 milligrams per litre of water for health purposes
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.
Entering the environment
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.
Where it ends up
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.
Sources of emissions
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.
Diffuse sources, and industry sources included in diffuse emissions data
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.
Sources used in preparing this information
- ANZECC (1992) Australian Water Quality Guidelines for Fresh and Marine Waters.
- Australian Water Resources Council Technical Paper No.7. AGPS
- Environmental Defense Fund (1998), Sodium nitrate: The Chemical Scorecard: (accessed, March, 1999)
- Environmental Defense Fund (1998), Sodium nitrite: The Chemical Scorecard: (accessed, March, 1999)
- Hart, B.T. (1974) A compilation of Australian Water Quality Criteria.
- Hem, J.D. 1985 Study and Interpretation of the Chemical Characteristics of Natural Water, USGS. 3rd Edition, Water Supply Paper 2254.
- National Environment Protection Council (1998), National Environment Protection Measure for the National Pollutant Inventory. (accessed, December, 1998)
- Technical Advisory Panel (1999), Final Report to the National Environment Protection Council.
- WHO 1992 Draft Guidelines for Drinking-Water Quality. PCS/EHC/92.60c World Health Organisation International Programme on Chemical Safety.
- Safe Work Australia, Workplace exposure standards for airborne contaminants, accessed March 2019.
- National Health and Medical Research Council (NHMRC), Australian Drinking Water Guidelines (2011) - Updated October 2017, accessed May 2018.