Organophosphorothioates

Organophosphorothioates are a subclass of organophosphorus compounds in which a sulfur atom replaces one of the non-bridging oxygens of the phosphate group, forming a phosphorothioate (P=S) moiety. This structural feature distinguishes them from phosphate and phosphorothioate analogues and influences their chemical behavior and toxicity. Many organophosphorothioates have been used as pesticides, particularly as insecticides and acaricides. Well-known members of this class include parathion and chlorpyrifos.

Action and effects: Organophosphorothioates inhibit acetylcholinesterase, leading to the accumulation of acetylcholine and overstimulation of cholinergic signaling. In vivo, metabolism can convert certain phosphorothioates to more toxic oxon forms. Toxicity is influenced by the specific substituents and the route of exposure; they can be highly toxic to humans and other non-target organisms at sufficient doses.

Properties and environmental fate: They are typically lipophilic, which facilitates dermal and oral absorption. They can undergo hydrolysis, oxidation, or dealkylation in the environment and within organisms. Depending on substituents and conditions, some compounds persist in soil and water while others degrade more rapidly. Their use is regulated in many countries due to acute toxicity and ecological risks.

Safety and regulation: Exposure is managed through safety guidelines, protective equipment, and proper handling procedures. Poisoning is treated with decontamination, atropine to counter muscarinic effects, and oximes such as pralidoxime to reactivate acetylcholinesterase where appropriate.