POTENTIAL BIOLOGICAL EFFECTS OF EMERGING CONTAMINANTS IN THE POTOMAC RIVER BASIN

During assessments to determine the cause(s) of fish kills and fish lesions in the South Branch of the Potomac river in 2003 a high prevalence of intersex was noted in smallmouth bass. Intersex, or the presence of characteristics of both sexes in a normally gonochoristic fish, has been used as an indicator of exposure to estrogenic compounds. Studies in this region have continued to document the spatial distribution of the problem within the Potomac/Shenandoah drainage, compare the prevalence with selected out of basin sites, determine if seasonal differences in prevalence occur and evaluate other species for intersex or other gonadal abnormalities. An intersex severity index was developed and the number of sections necessary to increase the probability of observing intersex if present was determined. Passive samplers were deployed at numerous sites during spring and fall (high flow and low flow) in an attempt identify potential causative substances. Sediment samples were also collected. Since amny of these substances may be additive in their effects, extracts of the passive samplers and sediment samples were used in testing estrogenicity and effects on immune cells utilizing both human cell lines and cell cultures from fish. Several lines of evidence suggest the presence of substances that are affecting both the reproduction and disease resistance of fish in the Potomac drainage.