Phosphine

Primary reference(s)

CDC, 2019. Phosphine. Centres for Disease Control and Prevention (CDC). Accessed 20 October 2020.

PHE, 2017. Phosphine: Health effects, incident management and toxicology. Public Health England (PHE). Accessed 20 October 2020.

Additional scientific description

Phosphine (PH₃) reacts violently with air, oxygen, oxidants such as chlorine and nitrogen oxides, metal nitrates, halogens and many other substances causing fire and explosion hazard. Pure phosphine is odourless, although most commercially available grades have the odour of garlic or decaying fish.

It attacks many metals. Phosphine decomposes on heating or burning, producing fumes including phosphorus oxides and liberates hydrogen when passed over heated metal (PHE, 2017a).

The major uses of phosphine are as a rodenticide and fumigant for stored agricultural products such as nuts, seeds, grains, coffee and tobacco, and in the manufacture of semi-conductors for the electronics industry. Phosphine is also used in the production of some chemicals and metal alloys and is an unintentional by-product in the illegal manufacture of the drug methamphetamine. Phosphine is also used as a condensation catalyst and in the manufacture of some polymers (PHE, 2017a).

Phosphine is rarely found in nature. Small amounts can be formed during the breakdown of organic matter, although it is rapidly degraded. Phosphine is released into the air via emissions from various manufacturing processes and from the use of metal phosphides (magnesium, aluminium, zinc), phosphide fumigants and pesticides (PHE, 2017a).

Metrics and numeric limits

Emergency response and acute exposure – there are Emergency Response Planning Guidelines (ERPGs) (NOAA, 2016) and Acute Exposure Guideline Values for Airborne Chemicals (AEGLs) (US EPA, no date).

Examples of drivers, outcomes and risk management

Phosphine is acutely toxic; exposure to high levels causes immediate effects. Exposure to low doses of phosphine causes nonspecific symptoms such as headache, dizziness, numbness, general fatigue, breathing difficulties (tightness around the chest, pain in the region of the diaphragm, cough) and gastrointestinal disturbance (pain, nausea, vomiting, diarrhoea). At higher doses, subjects may experience lung irritation, persistent coughing, tremors and convulsions, leading to pulmonary oedema, myocardial injury, kidney damage and coma, and sometimes death due to cardiovascular failure, usually within the first few hours or after a delay of up to two weeks in the case of liver failure (ATSDR, 2011; PHE, 2017a).

Chronic exposure to phosphine is unlikely to occur in the general population but may occur in an occupational setting. Symptoms of chronic exposure include anaemia, bronchitis, gastrointestinal disorders, speech and motor disturbances, weakness, weight loss, toothache, swelling of the jaw, mandibular necrosis, and spontaneous fractures. Some chronic effects can be confused with symptoms of acute poisoning (PHE, 2017a).

Phosphine is very highly toxic by inhalation. Major accidental release of stored phosphine presents a serious explosion/fire hazard and an acute toxic hazard for humans and animals. Chemical accidents associated with phosphine exposure have been reported in many countries. Accidental exposure of the general population to phosphine has occurred in association with fumigation operations and on-board ships carrying cargo capable of releasing phosphine (IPCS, 1988).

The most important factor in the safe handling of phosphine and metal phosphides, and in their formulation, is proper work practices (PHE, 2017b); evacuation should be considered in a written emergency plan for releases of phosphine (ILO/WHO, 2017) and harmonized labelling and transport approaches should be adhered to (ILO/WHO, 2017).