Organochlorine contamination in pinnipeds

Organochlorines, such as PCBs and DDT, are ubiquitous contaminants. Most studies reporting concentrations of organochlorines in pinnipeds have investigated ringed, grey, and harbour seals. Very few studies have been carried out on pinnipeds from the southern hemisphere. Pre-1980, the highest mean wet-weight blubber concentrations of DDT and related metabolites (911 +/- 582 micrograms g-1) were recorded in sea lions from California. The highest pre-1980 blubber concentrations of PCBs (1470 +/- 922 micrograms g-1) were recorded in harbour seals from the Netherlands. In later studies, the highest blubber concentrations of PCBs have been recorded from grey seals of the Dee estuary, UK [46.79 (10.17-116.68) micrograms g-1]. The highest DDT concentrations measured in individual pinnipeds appear to be in the 1-15 micrograms g-1 range, and such levels have been recorded from ringed, grey, and harbour seals and Australian fur seals. There are problems in identifying trends based on different studies. These include the improvement in analytical methods with time and the lack of uniformity in analytical methodology between laboratories as well as in the biological material analyzed. Insufficient standardized studies have been undertaken for a clear picture of temporal trends in DDT and PCB concentrations in pinniped tissues to be identified. Reported results show variations in contaminant concentrations between pinniped colonies from different sites, and special reference has been made to comparison of contaminant burdens between the UK colonies. Insufficient standardized information is currently available for patterns of contamination in pinnipeds to be assessed on a global scale. Many, although not all, studies have shown evidence for age and sex correlation for organochlorine concentrations in pinnipeds; male seals continuing to accumulate certain organochlorines throughout their lives; female seals accumulating these compounds until maturity when they lose part of their body burdens to their offspring via transplancental transfer and, more importantly, via lactation. The ability of pinnipeds to metabolize organochlorine compounds appears to be less well developed than in terrestrial mammals and seems to vary between seal species. Reported effects on pinnipeds, which have been suggested to result from organochlorine contamination, include skeletal deformities and impacts on reproduction, such as uterine blockages. The evidence of a relationship between recent epizootics in marine mammal populations and organochlorine pollution suggests that viruses and pollution are potential significant contributors to mortalities, but other factors, such as unseasonably warm temperatures and high seal densities, cannot be precluded.(ABSTRACT TRUNCATED AT 400 WORDS)