A role for solvents in the toxicity of agricultural organophosphorus pesticides.

Abstract

Organophosphorus (OP) insecticide self-poisoning is responsible for about one-quarter of global suicides. Treatment focuses on the fact that OP compounds inhibit acetylcholinesterase (AChE); however, AChE-reactivating drugs do not benefit poisoned humans. We therefore studied the role of solvent coformulants in OP toxicity in a novel minipig model of agricultural OP poisoning. Gottingen minipigs were orally poisoned with clinically relevant doses of agricultural emulsifiable concentrate (EC) dimethoate, dimethoate active ingredient (AI) alone, or solvents. Cardiorespiratory physiology and neuromuscular (NMJ) function, blood AChE activity, and arterial lactate concentration were monitored for 12h to assess poisoning severity. Poisoning with agricultural dimethoate EC40, but not saline, caused respiratory arrest within 30 min, severe distributive shock and NMJ dysfunction, that was similar to human poisoning. Mean arterial lactate rose to 15.6 [SD 2.8] mM in poisoned pigs compared to 1.4 [0.4] in controls. Moderate toxicity resulted from poisoning with dimethoate AI alone, or the major solvent cyclohexanone. Combining dimethoate with cyclohexanone reproduced severe poisoning characteristic of agricultural dimethoate EC poisoning. A formulation without cyclohexanone showed less mammalian toxicity. These results indicate that solvents play a crucial role in dimethoate toxicity. Regulatory assessment of pesticide toxicity should include solvents as well as the AIs which currently dominate the assessment. Reformulation of OP insecticides to ensure that the agricultural product has lower mammalian toxicity could result in fewer deaths after suicidal ingestion and rapidly reduce global suicide rates.

• Authors: Michael Eddleston, Jonathan M Street, Ian Self, Adrian Thompson, Tim King, Nicola Williams, Gregorio Naredo, Kosala Dissanayake, Ly-Mee Yu, Franz Worek, Harald John, Sionagh Smith, Horst Thiermann, John B Harris, R Eddie Clutton
• Journal: Toxicology (Toxicology) Vol. 294 Issue 2-3 Pg. 94-103 (Apr 11 2012) ISSN: 1879-3185 [Electronic] Ireland
• PMID: 22365945 (Publication Type: Comparative Study, Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Chemical References

• Cholinesterase Inhibitors
• Cyclohexanones
• Emulsions
• Insecticides
• Solvents
• Lactic Acid
• cyclohexanone
• Dimethoate

Topics

• Agriculture
• Animals
• Cholinesterase Inhibitors (administration & dosage, poisoning)
• Cyclohexanones (chemistry)
• Dimethoate (administration & dosage, poisoning)
• Emulsions
• Humans
• Insecticides (administration & dosage, poisoning)
• Lactic Acid (blood)
• Male
• Neuromuscular Junction (drug effects, metabolism)
• Respiratory Insufficiency (chemically induced)
• Shock (chemically induced)
• Solvents (chemistry)
• Species Specificity
• Swine
• Swine, Miniature