Organochlorine Residues in Maternal Blubber, Milk, and Pup Blubber from Grey Seals (Halichoerus grypus) from Sable Island, Nova Scotia

Abstract

Residues of DDT group insecticides and of PCBs were measured in samples of maternal blubber, milk, and pup blubber from grey seals (Halichoerus grypus) from Sable Island, N.S. Mean ΣDDT and PCB levels in maternal blubber lipid were 14.0 and 14.5 μg/g, respectively. Concentrations of DDT and PCBs in milk lipid were approximately 60 and 30%, respectively, of those found in maternal blubber lipid, suggesting a partial barrier to passage of these residues through mammary tissue. Concentrations in pup blubber lipid were the same as, or slightly higher than, those in milk lipid.We estimated that a grey seal will lose about 30% of its total ΣDDT burden and about 15% of its PCB burden through lactation; this would be approximately balanced by its estimated annual intake of these residues from food. Thus, the observation that female seals show no increase in residue burdens with age (in contrast to males) is explained. Key words: organochlorine, DDT, DDE, PCB, seal, blubber, milk