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

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.

Figure optionsDownload as PowerPoint slideHighlights▸ A new approach for the treatment of aluminium phosphide poisoning is proposed. ▸ Phosphine gas is responsible for aluminium phosphide toxicity. ▸ Phosphine gas and boric acid are considered as Lewis base and Lewis acid, respectively. ▸ Phosphine gas can be chemically trapped and neutralised by boric acid. ▸ Boric acid is proposed as a new possible antidote for aluminium phosphide poisoning.