Bioconcentration of Organochlorine Pollutants in Permanent and Deciduous Dentin of Sheep and Lambs

Objective: Organochlorine pollutants, due to their lipophilicity and persistence, accumulate in food chains and cause elevated contamination in human beings. We have previously shown that organochlorines cause developmental defects of enamel and are transferred from blood to dentine. The aim of this study was to investigate differences in the bioconcentration of individual organochlorines between permanent and deciduous dentine. Methods: Two actively lactating sheep were administered a single dose (1 µM/kg b.w.) of individual nonplanar (PCB-54) and planar (PCB-80) tetrachlorobiphenyls, and nonplanar (PCB-155) and planar (PCB-169) hexachlorobiphenyls, and two organochlorine pesticides, hexachlorobenzene (HCB) and dichlorodiphenyldichloroethene (DDE) by intramuscular injection. The sheep were sacrificed two months after exposure, and the lambs at the age of three months. The concentrations of organochlorines in dentine and blood were determined by high-resolution gas chromatography with electron capture detection. Results: The levels of PCB-54, -80, -155, -169, HCB, and DDE in permanent ovine dentine were 0.05, 0.36, 0.18, 0.17, 0.51, and 1.0, and in deciduous dentine of lambs <0.01, <0.01, 0.07, 10.7, 0.17, and 2.3 pM/g wet basis, respectively. The blood/dentine concentration ratios for PCB-155, -169, HCB, and DDE were 2, 135, 10, and 5-fold higher in sheep than in lambs, respectively. In deciduous dentine, higher levels of higher chlorinated, planar, more toxic, and metabolically persistent organochlorines were observed. Conclusion: Our results indicate that the bioconcentration of organochlorines is higher in deciduous than in permanent dentine. It is suggested that the physicochemical properties of individual organochlorines, i.e. lipophilicity, steric effect, sorption properties, metabolic stability, and tissue specific characteristics, i.e. composition, structure, perfusion, and metabolism, play a part in the bioconcentration. Supported by the Ministry of Science and Technology, Slovenia, Grant No. J3-8713-0381-99.