Transfer of PBDEs and chlorinated POPs from mother to pup during lactation in harp seals Phoca groenlandica

Seven mother–pup pairs of harp seal (Phoca groenlandica) were sampled during the lactation season near Magdalen Islands, QC, Canada. The blubber and serum of pups and mothers as well as the milk of mothers were analyzed for polybrominated diphenyl ethers and several chlorinated persistent organic pollutants (POPs) to evaluate their transfer prior to weaning. Principal component analysis demonstrated significant variations in contaminant distribution patterns between seal tissues of mothers and pups. The selectivity in the transfer of POPs between mothers and pups appeared mainly driven by their log Kow (octanol/water partition coefficient). The most selective transfer step for the POPs examined occurred between the blubber and the serum of the mother. A novel approach to examine temporal changes of POP concentrations in tissues of seals which take into account the contamination of mothers was developed. A general decrease of POP concentrations in pup tissues throughout lactation may suggest a growth dilution. A concomitant rise of POP concentrations was observed in maternal blubber and serum and in milk as lactation progresses. The intensive offloading of contaminants via lactation constitutes a major but selective excretory route for reproductive female seals and also a significant route of exposure for suckling pup seals.

► Significant variations in contaminant distribution patterns were observed between seal tissues of mothers and pups.
► The selectivity in the transfer of POPs between mothers and pups appeared mainly driven by their log Kow.
► The most selective transfer step for the POPs examined occurred between the blubber and the serum of the mother.
► The offloading of contaminants via lactation constitutes a major but selective excretory route for reproductive female seals.
► The offloading of contaminants via lactation constitutes also a significant route of exposure for suckling pup seals.