SURVEY OF RECEIVING-WATER ENVIRONMENTAL IMPACTS ASSOCIATED WITH DISCHARGES FROM PULP-MILLS .3. POLYCHLORINATED DIOXINS AND FURANS IN MUSCLEAND LIVER OF WHITE SUCKER (CATOSTOMUS-COMMERSONI)

Polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) we re measured in white sucker liver samples from seven pulp and paper mi ll sites, and three reference sites in Ontario. The mills included fiv e bleached-kraft mills, with and without secondary treatment, and two sulfite-mechanical mills. 2,3,7,8-T4CDD and 2,3,7,8-T4CDF were the dom inant congeners detected in both liver and fillet samples at all of th e pulp and paper mill sites, with mean 2,3,7,8-T4CDD toxic equivalent concentrations (TEQs) as high as 124 pg g-1 in liver tissue. Concentra tions of PCDDs/PCDFs in liver tissues were several fold higher than in fillet tissue, but this difference can be accounted for by lipid norm alization. Biological information, including liver weight, gonad weigh t, MFO activity (ethoxyresorufin-0-deethylase, EROD), and plasma sex s teroids, was measured on individual fish. There was no relationship be tween TEQs and condition factor, gonadosomatic index, liver somatic in dex, or circulating plasma 11-ketotestosterone. A weak negative correl ation was observed between circulating plasma testosterone and TEQs. A lthough there was a positive correlation (r = 0.49, p < 0.001) between MFO activity (EROD) and TEQ, one site with very low chlorine use and low TEQs had EROD activity similar to levels observed at more contamin ated sites. This finding, along with recent observations that MFO acti vity is rapidly cleared in pulp-mill-''posed fish, casts doubt on an e xclusive causal relationship between MFO activity and PCDDs/PCDFs at t hese sites.