Transfer kinetics to egg yolk and modeling residue recovered in yolk of readily metabolized molecules: Polycyclic aromatic hydrocarbons orally administered to laying hens

The kinetic of transfer into egg yolk of Persistent Organic Pollutants with contrasting properties regarding biotransformation and bioaccumulation was investigated. Twenty-four Hy line hens, aged 26 weeks, were orally administered, during 1 or 3 consecutive days, 6 mg of a mixture of three PAHs (phenanthrene, pyrene, benzo[a]pyrene) in equal amounts (w:w) or 3 mg of lindane per kg body weight daily. Each day, contaminants were administered 1 h after oviposition in one gelatin capsule. Eggs were collected daily during the 12 d following the first dosing. Concentrations of PAHs and their main hydroxylated metabolites in yolk were determined using HPLC coupled with fluorimetric detection, while lindane was analysed by GC–ED. At the end of the experiment, hens were sacrified and preovulatory yolks were collected and weighed.All three PAHs were recovered in yolks, mainly as metabolites, indicating an active biotransformation of these compounds in hens. Within 10 d, PAHs and metabolites concentrations in yolks were back to initial values. However, the recovery rate of these compounds to yolk calculated over the 12-d experiment, was very low, reaching 0.089%, 0.034% and 0.006% for Phe, Pyr and B[a]P, respectively. Daily deposition of yolk and of PAHs and metabolites were found to be directly proportional, indicating that no significant body storage of these PAHs occurred and that they were rapidly hydroxylated after ingestion. In contrast, lindane and yolk deposition could not be related. Storage of lindane in body fat explains its slower elimination via eggs.