ORGANOCHLORINE-ASSOCIATED IMMUNOSUPPRESSION IN PREFLEDGLING CASPIAN TERNS AND HERRING-GULLS FROM THE GREAT-LAKES - AN ECOEPIDEMIOLOGICAL STUDY

The objectives of this study were to determine whether contaminant-ass ociated immunosuppression occurs in prefledgling herring gulls and Cas pian terns from the Great lakes and to evaluate immunological biomarke rs for monitoring health effects in wild birds. During 1992 to 1994, i mmunological responses and related variables were measured in prefledg ling chicks at colonies distributed across a broad gradient of organoc hlorine contamination (primarily polychlorinated biphenyls), which was measured in eggs. The phytohemagglutinin skin test was used to assess T-lymphocyte function. in both species, there was a strong exposure-r esponse relationship between organochlorines and suppressed T-cell-med iated immunity. Suppression was most severe (30-45%) in colonies in La ke Ontario (1992) and Saginaw Bay (1992-1994) for both species and in western Lake Erie (1992) for herring gulls. Both species exhibited bio logically significant differences among sites in anti-sheep red blood cells antibody titers, but consistent exposure-response relationships with organochlorines were not observed. in Caspian terns and, to a les ser degree, in herring gulls, there was an exposure-response relations hip between organochlorines and reduced plasma retinol (vitamin A). In 1992, altered white blood cell numbers were associated with elevated organochlorine concentrations in Caspian terns but not herring gulls. The immunological and hematological biomarkers used in this study reve aled contaminant-associated health effects in wild birds. An epidemiol ogical analysis strongly supported the hypothesis that suppression of T-cell-mediated immunity was associated with high perinatal exposure t o persistent organochlorine contaminants.