Distribution and clearance of pentachloronitrobenzene in chickens

Abstract

Pentachloronitrobenzene (PCNB) is an effective, broad-spectrum fungicide. Grains used in animal feeds may contain residues of PCNB. Technical grade PCNB (10% corn oil solution) was added to laying mash and fed to Comet Red and White Leghorn chickens at dietary levels of up to 300 ppm for 16 weeks. The hens were then returned to control diet (clearance phase). The concentrations of PCNB; its impurities, pentachlorobenzene (PCB), hexachlorobenzene (HCB), and tetrachloronitrobenzene (TCNB); and its metabolites, pentachloroaniline (PCA) and pentachlorothioanisole (PCTA), were determined periodically in eggs and excreta, and in various tissues taken at necropsy. Concentrations of PCNB, PCA, and PCTA reached a plateau in tissues and eggs by the second week while HCB and PCB concentrations continued to increase throughout the feeding phase. Excreta were found to contain traces of PCNB, PCA, and PCB. TCNB was not detected in any samples. There were no detectable strain differences in distribution or biotransformation. No effects upon weight gain or egg production were observed nor were there any gross pathologic lesions. During the clearance phase, PCNB, PCA, and PCTA were undetectable by the 16th-week, while HCB and PCB remained at levels > 0.002 ppm through 1 year of clearance. The half-life of HCB was determined to be 90 days. The level of HCB in edible tissues and eggs, extrapolated to their maximum possible steady-state concentration, were determined not to pose a health hazard to humans, when chickens are fed diets containing PCNB at 300 ppm.