An update on toxicology of aluminum phosphide

Abstract

Aluminum phosphide (AlP) is a cheap solid fumigant and a highly toxic pesticide which is commonly used for grain preservation. In Iran it is known as the “rice tablet”. AlP has currently aroused interest with increasing number of cases in the past four decades due to increased use in agricultural and non-agricultural purposesand also its easy availability in the markets has increased its misuse to commit suicide. Upon contact with moisture in the environment, AlP undergoes a chemical reaction yielding phosphine gas, which is the active pesticidal component. Phosphine inhibits cellular oxygen utilization and can induce lipid peroxidation. It was reported that AlP has a mortality rate more than 50% of intoxication cases. Poisoning with AlP has usually occurred in attempts to suicide. It is a more common case in adults rather than teen agers. In some eastern countries it is a very common agent with rapid action for suicide. Up to date, there is no effective antidote or treatment for its intoxication. Also, some experimental results suggest that magnesium sulfate, N-acetyl cysteine (NAC), glutathione, vitamin C and E, beta-carotenes, coconut oil and melatonin may play an important role in reducing the oxidative outcomes of phosphine. This article reviews the experimental and clinical features of AlP intoxication and tries to suggest a way to encounter its poisoning.

Chemical Reaction between Boric Acid and Phosphine Indicates Boric Acid as an Antidote for Aluminium Phosphide Poisoning

“…10,11 AlP poisoning is more prevalent in Iran and India. 2,3 Many reports have proposed experimental or individual case treatments for A1P poisoning, including digoxin; N-acetylcysteine; hyperbaric oxygen; magnesium ( 25 Mg 2+ )-carrying nanoparticles; intragastric irrigation with sweet almond oil; a combination of vitamin C and methylene blue; extensive gastric lavage with coconut oil and a sodium bicarbonate solution with simultaneous aspiration; perfusion with an intraaortic balloon pump; Nω-nitro-L-arginine methyl ester; a combination of atropine and pralidoxime; and trimetazidine. [12][13][14][15][16][17][18][19][20][21] However, no specific antidote has yet been found for the routine treatment of AlP poisoning and unfortunately most people who are poisoned do not survive.…”

“…[12][13][14][15][16][17][18][19][20][21] However, no specific antidote has yet been found for the routine treatment of AlP poisoning and unfortunately most people who are poisoned do not survive. [2][3][4] Recently, boric acid has been theoretically proposed as an antidote for AlP poisoning. 1 With the formula B(OH) 3 , boric acid is a Lewis acid with an empty p orbital which can accept electrons.…”

“…Although AlP is not toxic per se, the pesticide releases phosphine (PH 3 )-a colourless, water insoluble, flammable and highly toxic gas-after coming into contact with water. [1][2][3] The gas is produced according to the following chemical equation: 4 While odourless in its pure form, PH 3 can smell of garlic or decaying fish due to the presence of impurities such as substituted phosphines and diphosphines.…”

“…This greatly reduced production of gas may be due to the surface chemistry of AlP tablets and may also explain why reduced mortality and fewer systemic effects have been reported among individuals who have ingested fragmented or powdered forms of AlP. 2,27,28 In nearly all animal studies, the AlP tablet is administered by gastric gavage in powdered form in a carrier such as peanut oil, almond oil or normal saline; 15,16,29 this method of poisoning may therefore be incorrect because fragmentation or powdering interferes with PH 3 gas evolution. Thus, examining oral AlP poisoning in animal studies is very difficult; instead, it is recommended that the animals be poisoned by PH 3 gas.…”

“…2 These amounts are equivalent to 49.3-164.2 mg of PH 3 gas. Therefore, 150-500 mg of AlP was deemed approximately equivalent to 26-87 mL of gas in the acidic environment of the stomach, at 37 °C and under 101.325 kPa.…”