INDEX cholinesterase inhibitors

The Committee examined five organophosphate pesticides (acephate, chlorpyrifos, dimethoate, disulfoton, and ethion), which are all cholinesterase inhibitors and may be present as residues in fruits and vegetables. Chlorpyrifos was used as the index compound. The TEF was defined as the ratio of the NOAEL or LOAEL for each pesticide to the NOAEL or LOAEL for chlorpyrifos. TEFs based on LOAELs were used when a NOAEL could mot be established for two of the compounds. 

The UK Pesticide Safety Directorate (PSD) has decided to use the TEF approach for assessment of combined risk from exposure to mixtures of acetyl cholinesterase inhibitors (organophosphate (OP) compounds and carbamates) (PSD 1999). Despite clear differences in the action of carbamates and OP compounds, the index compounds selected for all acetyl cholinesterase inhibitors were either aldicarb (carbamate) or chlorpyrifos (OP). The POD for determining relative potency was predetermined as the dose level that produced 20% inhibition of red blood cell cholinesterase in a 90-day dietary study in rats. 

Properties Colorless clear vise, liq. mild odor sol. in most org. soivs., 95% ethanol, acetone, DMSO, ketones, chlorinated hydrocarbons sol. < 1 mg/ml in water insol. in aliphatic hydrocarbons m.w. 430.91 dens. 1.508 g/cm (22.2 C) vapor pressure 10.3 mm Hg (25 C) f.p. 27 C b.p. 236-237 C (5 mm) flash pt. 252 C ref. index 1.5022 Toxicology LD50 (oral, rat) 1850 mg/kg, (skin, rabbit) > 23,700 mg/kg mod. toxic by ing. may cause irritation of skin, respiratory tract cholinesterase inhibitor may cause tremors, convulsions, irritability, hypermotility, diarrhea, enzyme inhibition, change in blood/tissue levels, changes in liver/kidney wt questionable carcinogen experimental teratogen and reproductive effects mutagenic data ... 

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