Ammonia

Primary reference(s)

WHO, 1986. Environmental Health Criteria 54: Ammonia. 10.4, Accidental exposure. International Programme on Chemical Safety, World Health Organization (WHO). Accessed 2 December 2019.

PHE, 2019. Ammonia: Health effects, incident management and toxicology. Public Health England (PHE). Accessed 3 September 2020.

Additional scientific description

Ammonia is a non-flammable gas but is treated as flammable because it can form explosive mixtures with air. Ammonia dissolves readily in water. Solutions of ammonia are alkali and can be corrosive when concentrated or mixed with water. In addition to irritation symptoms, delayed onset of serious respiratory symptoms may present, including corrosive damage to the mucous membranes of both the upper and lower respiratory tract (WHO, 1986; PHE, England 2019).

Although ammonia is lighter than air, the vapours from a leak will initially hug the ground. Long-term exposure to low concentrations or short-term exposure to high concentrations may result in adverse health conditions from inhalation. Prolonged exposure of containers to fire or heat may result in their violent rupturing and rocketing. Both liquid and vapours are extremely irritating, especially to the eyes (Cameo Chemicals, no date).

Ammonia is an extensively used industrial chemical. It is commonly used in the production of fertilisers, fibres and plastics, and explosives and is also widely used as a cleaning and descaling agent and in food additives and as industrial refrigerant (WHO, 1986).

High gaseous ammonia concentrations may be encountered locally, both in domestic and occupational environments, as a result of gaseous emissions and/or spillages of concentrated solutions, and respiratory (and skin and eye) injury may result. On a larger scale, spillage from stock or transport tanks or refrigeration plant of concentrated ammonia liquor or anhydrous ammonia would constitute severe environmental damage and would cause serious injury to people, animals, and plants in the vicinity. Owing to its low density and short bio-persistence, major spillages would be expected to disperse rapidly and not to persist in the environment (WHO, 1990).

Ammonia can be stored and transported as a liquid at a pressure of 10 atm at 25°C. Ammonia dissolves readily in water where it forms, and is in equilibrium with ammonium ions (NH4+). The sum of ammonia and ammonium concentrations is termed ‘total ammonia’ and, owing to the slightly different relative molecular masses, may be expressed as ‘total ammonia-nitrogen (NH3-N)’. In most waters, NH4+ predominates, but increased pH or temperature or decreased ionic strength may materially increase levels of non-ionized ammonia (WHO, 1986).

Metrics and numeric limits

Drinking-water: There is no health-based standard proposed by the World Health Organization (WHO) for ammonia in drinkingwater. This is because the odour threshold (1.5 mg/l) and taste threshold (35 mg/l) are considered to be below levels of health concern (WHO, 2011). However, ammonia has the potential to reduce the effectiveness of some water treatment techniques and so some countries do prescribe a guideline value.

Air: There are no air quality guidelines for ambient levels of ammonia and public health. However, individual countries may develop occupational exposure limits and adopt acute/emergency guidelines.

Emergency response and acute exposure: Emergency Response Planning Guidelines (ERPG) (NOAA, 2016) and Acute Exposure Guideline Values for Airborne Chemicals (AEGLs) (US EPA, no date) exist for ammonia as a result of health risks associated with larger releases of ammonia in accident scenarios.

Examples of drivers, outcomes and risk management

Breathing in low levels of ammonia may cause irritation to the eyes nose and throat. High levels of ammonia may cause burns and swelling in the airways, lung damage and can be fatal. Ingestion of ammonia solutions can cause pain and burns throughout the digestive tract. In severe cases the respiratory system, stomach and heart may be damaged, and death may follow. Strong ammonia solutions may cause serious burns if splashed on the skin. At high concentrations, gases and fumes of ammonia can also cause corrosive damage to the skin. Splashes in the eye may cause damage which may be irreversible in some cases and can lead to loss of sight. The health effects of ammonia are usually immediate and long-term effects would not be expected after exposure to small amounts (PHE, 2019).

Anhydrous ammonia (liquid or gas) reacts with tissue water to form the corrosive solution ammonium hydroxide. Following body surface exposure, it is advised to disrobe, and improvised wet decontamination should be considered. Spillages and decontamination run-off should be prevented from entering watercourses (PHE, 2019).

Risk management 

• Consider evacuation where spillage or leakage has occurred.
• Improving wet decontamination should be considered in the case of skin contamination as ammonia reacts with tissue water to form the corrosive solution ammonium hydroxide (PHE, 2019).
• Spillages and decontamination run-off should be prevented from entering watercourses (PHE, 2019) due to potential damage to plants and animals.
• Encourage the avoidance of agricultural land during the use of ammonia fertilisers (ATSDR, 2004).
• Harmonised labelling and transport approaches should be considered.