Proposing boric acid as an antidote for aluminium phosphide poisoning by investigation of the chemical reaction between boric acid and phosphine

Abstract

Aluminium phosphide (AlP) is a storage fumigant pesticide, which is used to protect stored grains especially from insects and rodents. It releases phosphine (PH₃) gas, a highly toxic mitochondrial poison, in contact with moisture, particularly if acidic. Although the exact mechanism of action is unknown so far, the major mechanism of PH₃ toxicity seems to be the inhibition of cytochrome-c oxidase and oxidative phosphorylation which eventually results in adenosine triphosphate (ATP) depletion and cell death. Death due to AlP poisoning seems to be as a result of myocardial damage. No efficient antidote has been found for AlP poisoning so far, and unfortunately, most of the poisoned human cases die. PH₃, like ammonia (NH₃), is a Lewis base with a lone-pair electron. However, boric acid (B(OH)₃) is a Lewis acid with an empty p orbital. It is predicted that lone-pair electron from PH₃ is shared with the empty p orbital from B(OH)₃ and a compound forms in which boron attains its octet. In other words, PH₃ is trapped and neutralised by B(OH)₃. The resulting polar reaction product seems to be excretable by the body due to hydrogen bonding with water molecules. The present article proposes boric acid as a non-toxic and efficient trapping agent and an antidote for PH₃ poisoning by investigating the chemical reaction between them.