chlorpyrifos

Chlorpyrifos is an organophosphate insecticide that has been widely used in agriculture to control a broad range of pests on crops such as fruits, nuts, grains, vegetables, and cotton. It has also been employed in some urban pest-control applications.

Chlorpyrifos acts by inhibiting acetylcholinesterase, an enzyme that breaks down acetylcholine in nervous tissue. Inhibition leads to the accumulation of acetylcholine and overstimulation of cholinergic pathways. Symptoms of exposure range from headache and dizziness to nausea, sweating, muscle weakness, and in severe cases, respiratory distress. Acute toxicity is a central concern for farm workers and bystanders, and risks are heightened under improper handling or chronic exposure.

Because chlorpyrifos affects non-target organisms, it has raised ecological and health concerns. It is toxic to birds, aquatic organisms, and pollinators, and multiple studies have linked fetal and early-childhood exposure to neurodevelopmental effects. Regulatory actions in several countries have restricted or banned its use, and safe handling and protective equipment are required for workers where its use is permitted.

In the environment, chlorpyrifos degrades in soil and water through hydrolysis and photolysis, producing products such as 3,5,6-trichloro-2-pyridinol. It is moderately persistent in soil and can contaminate water near treated fields.

Regulatory status varies by jurisdiction. The European Union banned all uses of chlorpyrifos in 2020 due to health concerns. Other countries and regions have imposed restrictions or phased reductions in agricultural use, while some still permit restricted use under label instructions.