Effect of an organophosphorus insecticide on brain cholinesterase activity in white-throated sparrows exposed to aerial forest spraying.
Brain cholinesterase (ChE) inhibition and fenitrothion residues were determined in white-throated sparrows (Zonotrichia albicollis) that had been exposed to aerial applications of fenitrothion (against Choristoneura fumiferana (Clem.) in forests in New Brunswick) in the breeding seasons of 1978 and 1979. Brain ChE activity was found to be significantly reduced, and fenitrothion and metabolite residues were detected in all the birds exposed. However, there was no consistent correlation between residues and brain ChE activity. An acute brain ChE response, manifested as sudden reduction followed by gradual recovery, was observed in birds exposed to 420 g a.i./ha, whereas a chronic response, manifested as progressive ChE reduction, occurred at 210 g/ha.