Neurotoxicity of two organophosphorus ester flame retardants in hens

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Abstract
Delayed neurotoxicity in hens was reported after the administration of several chlorinated alkyl phosphates. Neurotoxicity increased in a homologous series with the size and/or hydrophobic nature of substituents. Neurotoxicities of 2 commercial flame retardants, Fyrol PCF [tri(2-chloropropyl) phosphate] and Fyrol CEF [tri(.beta.-chloroethyl) phosphate], were compared in adult White Leghorn hens. When Fyrol PCF (10 ml/kg neat) was administered orally to 4 hens, no inhibition of plasma cholinesterase or brain neurotoxic esterase was evident 24 h later. Fyrol CEF (10 ml/kg neat) produced significantly greater inhibition of plasma cholinesterase (87.1%) and brain neurotoxic esterase (30.0%). Since neither compound produced > 75% neurotoxic esterase inhibition, they were not expected to produce delayed neurotoxicity in hens. This was verified in hens treated twice with Fyrol PCF (10 ml/kg neat) or Fyrol CEF (10 ml/kg neat) and observed for 6 wk. Neither group showed behavioral or histopathologic evidence of delayed neurotoxicity. Measurement of neurotoxic esterase predicted the lack of potential of the 2 flame retardants to induce delayed neurotoxicity in hens.