Investigating potential associations between chronic exposure to polychlorinated biphenyls and infectious disease mortality in harbour porpoises fromEngland and Wales

Bioaccumulation of immunosuppressive organochlorines like polychlorinated b iphenyls (PCBs) may pose a threat to the health and viability of cetacean p opulations. To investigate possible associations between chronic exposure t o PCBs and infectious disease mortality in harbour porpoises Phocoena phoco ena in UK waters, blubber concentrations of 25 individual chlorobiphenyl (C B) congeners in 34 healthy harbour porpoises that died due to physical trau ma (mainly by-catch) were compared with CB concentrations in 33 animals tha t died due to infectious disease. The infectious disease group had signific antly greater total 25 CBs (Sigma 25CBs) concentrations than the physical t rauma group (P < 0.001). The mean Sigma 25CBs concentration in animals that died due to physical trauma was 13.6 mg kg(-1) extractable lipid whereas t he mean concentration in the infectious disease group was 31.1 mg kg(-1) ex tractable lipid, The relationship between higher Sigma 25CBs and the infect ious disease group was not confounded by age, sex, nutritional status, seas on, location or year of stranding. In addition, adult females had significa ntly lower Sigma 25CBs levels than adult males (P < 0.05) due to maternal t ransfer of CBs to offspring. These findings are consistent with the hypothe sis that chronic PCB exposure predisposes harbour porpoises in UK waters to infectious disease mortality, although further research is required to tes t these associations more robustly. (C) 1999 Elsevier Science B.V. All righ ts reserved.