organophosphates

Organophosphates are organic compounds containing phosphorus bonded to oxygen and carbon substituents. They form a broad class that includes agricultural insecticides, industrial flame retardants, and some nerve-agent precursors. The defining feature is their potential to inhibit acetylcholinesterase, an essential enzyme in nerve signal transmission.

Chemically they include esters of phosphoric acid and related thio- or phosphorothioate derivatives. They vary in structure and lipophilicity, influencing volatility, environmental persistence, and biological uptake. Some require bioactivation to become potent AChE inhibitors.

Mechanism and toxicity: Organophosphates inhibit acetylcholinesterase by phosphorylating the active-site serine, causing accumulation of acetylcholine at cholinergic synapses. Clinically, this produces muscarinic symptoms (salivation, lacrimation, urination, defecation, GI distress, miosis), nicotinic symptoms (muscle fasciculations and weakness), and CNS disturbances. Treatment includes rapid decontamination, atropine to block muscarinic effects, and oximes such as pralidoxime to reactivate the enzyme if given before aging; benzodiazepines may be used for seizure control.

Uses and regulation: Pesticides such as chlorpyrifos, diazinon, malathion, and parathion have been widely used but many are subject to bans or restrictions due to harm to humans and wildlife. In industry, organophosphates serve as flame retardants and plasticizers. The most toxic counterparts, nerve agents such as sarin, soman, tabun and VX, are tightly controlled under international law.

Environmental fate and safety: Degradation occurs by hydrolysis and biological processes; many organophosphates degrade relatively quickly, but some persist and can accumulate in ecosystems. They can be toxic to aquatic life and birds. Safe handling requires protective equipment, proper storage, spill response, and adherence to regulatory exposure limits.