DEFORMITIES, PCBS, AND TCDD-EQUIVALENTS IN DOUBLE-CRESTED CORMORANTS (PHALACROCORAX-AURITUS) AND CASPIAN TERNS (HYDROPROGNE-CASPIA) OF THE UPPER GREAT-LAKES 1986-1991 - TESTING A CAUSE-EFFECT HYPOTHESIS

Deformities have been reported in many species of colonial waterbirds from several localities an the Laurentian Great Lakes. The hypothesis that deformities were caused by either polychlorinated biphenyls (PCBs ) or contaminants measured as 2,3,7,8-tetrachlorodibenzo-p-dioxin equi valents (TCDD-EQs) is tested in this review of available data on conce ntrations of contaminants in eggs and observed deformities in embryos and chicks of double-crested cormorants (Phalacrocorax auritus) and Ca spian terns (Hydroprogne caspia) between 1986 and 1991. Hatched chicks , live and dead eggs retrieved from 37 colonies in the upper Great Lak es were assessed for gross anatomical deformities. Rates of embryo dea th from seven regions of the upper Great Lakes were measured annually between 1986-1991. Half the embryos found dead in eggs were deformed. Nineteen types af abnormalities or deformities were observed. Subcutan eous edema ill cormorants and gastroschisis In terms were the most com mon abnormalities in live or dead Eggs. One of ten crossed-billed corm orant embryos survived to hatch. Pile bill-deformed terns hatched alth ough tern embryos had a greater rate of crossed-bills than cormorants. The suite of deformities and abnormalities found Mns similar to that produced in chickens by exposure to planar polychlorinated biphenyl (p PCB) and dioxin congeners. Hatching and deformity rates were correlate d with concentrations of pPCBs and TCDD-Eas. Planar PCB congeners that contributed most of the TCDD-EQs Mere present at concentrations suffi cient to cause the observed effects. TCDD-EQs measured by H4IIE rat he patoma cell 7-ethoxyresorufin O-decthylase (EROD) bioassay were highly correlated with deformity rates observed in cormorant chicks, live an d dead eggs, and egg death rates. Similar correlations of TCDD-EQs wit h deformity rates were found in hatched tern chicks, dead eggs, and eg g death rates, but not in live eggs. TCDD-EQs were more highly correla ted to deformity and embryo death rates than total PCBs. The weight of evidence and these data are sufficient to reject the null hypothesis that there is no causal relationship between the incidence of deformit ies in cormorants and ferns and exposure to planar halogenated compoun ds measured as TCDD-EQs or total PCBs in the Great Lakes.