EVALUATION OF TOXIC EFFECTS OF THE ORGANOPHOSPHORUS INSECTICIDE AZINPHOS-METHYL IN EXPERIMENTALLY AND NATURALLY EXPOSED BIRDS

Laboratory and field studies were conducted to evaluate the effects of the organophosphorus insecticide, azinphosmethyl, on bird populations and into the possibility of assessing toxic hazard by a non-destructive biomarker such as BChE inhibition. Japanese quail were treated with increasing doses of azinphos-methyl (0.5, 5, and 50 mg/kg) and sacrificed 7 and 24 h later. Serum BChE and CbE, brain AChE, and liver microsomal CbE activities showed different patterns of inhibition. The maximum inhibition of BChE and CbE usually occurred 7 h after treatment, whereas the effect on AChE was greater at 24 h. A positive correlation was found between BChE and AChE, 7 and 24 h after treatment. This correlation could serve as the foundation for a theoretical model for assessing toxic hazard through non-destructive biomarkers. The only effect on brain AChE was detected in the group treated with the highest concentrations of azinphos-methyl (50 mg/kg). Fugacity model calculations showed that such massive concentrations are very unlikely to occur under natural conditions after agricultural use of the compound. The non-destructive biomarker was used to test a population of tree sparrows living in a cherry orchard sprayed once with azinphos-methyl. No inhibition of BChE activity was found 24 h after application, and it was therefore concluded that the concentration of the insecticide used did not constitute a hazard for the birds.