SUBCHRONIC NEUROTOXICITY OF OIL FORMULATIONS CONTAINING EITHER TRICRESYL PHOSPHATE OR TRI-ORTHOCRESYL PHOSPHATE

This study was conducted to determine the threshold concentration of t ricresyl phosphate (TCP) in aviation engine oil able to cause delayed peripheral neuropathy in adult hens after repeated exposure. The study also evaluated the predictive value of endpoints usually used to meas ure acute peripheral neurotoxicity (neurotoxic esterase [NTE] inhibiti on, ataxia, and histopathologic changes), as measures of neurotoxicity in a subchronic study. Animals that received oil containing 3% TCP sh owed significant neurotoxicity that could not be accounted for by the small amount of TOCP present. Oil containing 1% TCP was without neurot oxic activity. There was an excellent correlation between percentage i nhibition of NTE and development of neuropathy. An association was als o seen for ataxia and neuropathology. Further study is needed to deter mine the phosphate ester isomers responsible for the significant neuro toxic potency demonstrated by the aviation engine oil containing 3% TC P.