SURVEY OF RECEIVING-WATER ENVIRONMENTAL IMPACTS ASSOCIATED WITH DISCHARGES FROM PULP-MILLS .4. BIOASSAY-DERIVED 2,3,7,8-TETRACHLORODIBENZO-P-DIOXIN TOXIC EQUIVALENT CONCENTRATION IN WHITE SUCKER (CATOSTOMUS-COMMERSONI) IN RELATION TO BIOCHEMICAL INDICATORS OF IMPACT

The H4IIE rat hepatoma bioassay was used to measure 2,3,7,8-tetrachlor odibenzo-p-dioxin toxic equivalent concentrations (TECs) in livers of white sucker (Catostomus commersoni) collected downstream from eight O ntario pulp mills and five reference sites. Subsamples of liver were a lso chemically analyzed for dioxins and furans. Bioassay-derived TECs were compared with TECs calculated from chemical residues using toxic equivalency factors (TEFs) specifically generated for the H4IIE cell l ine. This indicated that the bioassay-derived TECs could be accounted for largely by the additive effect of the dioxin and furan congeners. Seven of the eight examined mills had significantly higher TECs than t he corresponding reference locations. The bioassay-derived TECs were h ighest at mills that used kraft pulping and chlorine bleaching. Althou gh lower than the kraft mills, the thermomechanical (TMP) and sulfite mills also had higher TECs than the adjacent reference locations. The TECs were compared with hepatic 7-ethoxyresorufin-0-deethylase activit y (EROD), as well as with concentrations of the plasma steroid hormone s 17beta-estradiol, 11-ketotestosterone, and testosterone. Significant correlations were found between EROD activity and TECs in both male a nd female white sucker. The correlation for males was stronger than th at for females. Some of the variability in this relationship for femal es could be explained by a multivariate regression that added 17beta-e stradiol to the analysis; a strongly negative relationship between 17b eta-estradiol and EROD activity was superimposed on the positive EROD- TEC relationship. No significant correlations were found between TECs and 11-ketotestosterone in males, 17beta-estradiol in females, and gon adosomatic indexes in either sex. There were significant negative corr elations between TECs and testosterone in both sexes.