DISEASES AND ENVIRONMENTAL CONTAMINANTS IN SEALS FROM THE BALTIC AND THE SWEDISH WEST-COAST

Investigations have shown that Baltic grey seal (Halichoerus grypus) a nd ringed seal (Phoca hispida) suffer from a disease complex described as a primary lesion in the adrenals causing secondary reactions in va rious other organs. Studies on historical Baltic grey seal skull bone material show that the prevalence of affected animals started to incre ase after World War II. The disease complex explains the dramatic decr ease in the Baltic grey and ringed seal population during the 1960s an d 1970s and is believed to be caused by environmental pollutants. In 1 988, about 60% of the harbor seal population (Phoca vitulina) along th e Swedish west coast and in the southwestern part of the Baltic died i n the PDV epizootic (Phocine Distemper Virus). Whether the course of t he epizootic was altered by environmental pollutants is still an open question. Studies on historical harbor seal skull bone material from b oth the Baltic and the Swedish west coast show that the incidence of s kull bone lesions has also increased in these populations since World War II, indicating the presence of unnatural stress factors. After the epizootic, the harbor seal populations both in the Baltic and along t he Swedish west coast have increased in number. Chemical analysis of t issues has been performed on the three seal species collected in vario us areas of the Baltic and the Swedish west coast. The concentrations of 17 metals and non-metal elements, sDDT and PCBs, DDE and PCB methyl sulfones, toxaphene, chlordanes, polybrominated diphenyl ethers, PCDDs and PCDFs have been determined in selected groups of seals in order t o determine spatial, species and age variations in concentrations. Fur thermore, healthy animals have been compared to diseased animals. Spat ial variation was found mostly within the group of organohalogenated c ompounds, a group of contaminants where a strong covariation between t he various compounds was also found. On the basis of the analytical re sults as well as the pathological findings on Baltic seals, the group of DDE and PCB methyl sulfones is tentatively suggested to be more imp ortant in explaining the disease complex than coplanar structures incl uding dioxins.