Neurotoxicity of two organophosphorus ester flame retardants in hens

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. In the present study the neurotoxicities of two 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 four 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 greater than 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 correctly predicted the lack of potential of the two flame retardants to induce delayed neurotoxicity in hens.