Residues of fenitrothion in chick embryos following exposure of fertile eggs to this organophosphorus insecticide

SUMMARY The purpose of the study was to investigate whether the broadly applied insecticide fenitrothion was able to penetrate the avian eggshell following exposure to Sumithion 50 EC (50 % fenitrothion) by immersion. Residues were quantified in yolk and embryonic samples, and two widely used routes of exposure (injection and immersion) were compared in terms of residues. In the first part of the experiment, fertile hen’s eggs (Shaver Starcross 288) were immersed in a 0.33% aqueous solution of Sumithion 50 EC on day 0 or day 12 of incubation, while in the second part of the experiment eggs were injected with 0.1 ml of water/DMSO solution (9:1, v/v) containing 0.15 mg fenitrothion having the same exposure time. Following day 0 exposure, eggs were incubated until day 12, and eggs treated on day 12 were incubated until day 19. For gas chromatographic analysis, eggs exposed to the insecticide on day 0 were sampled on days 1, 3, 6, 9 and 12, while from eggs treated on day 12 samples were taken on days 13, 15 and 19. We demonstrated that fenitrothion was able to cross the eggshell after external exposure and contaminate the developing embryo with a penetration rate that increased after the mobilisation of Ca from the eggshell. The fenitrothion residues measured in the samples indicated that the embryos were contaminated by the chemical for a longer time after external exposure than after administration of the insecticide by injection. Moreover, the data suggest that fenitrothion appearing at distinct embryonic developmental stages after exposure by immersion and injection might have different toxic effects on the embryo. These findings suggest that external exposure cannot be simulated by the injection method ; however, the latter is also a relevant technique for egg treatment in toxicology studies.