oxin (e.g., dissolved) is not necessary for the development of regulations. The development of an appropriate risk equation will enable regulators to d e t e r m i n e h u m a n h e a l t h risks associated with contaminated sediments based on the integration of e q u i l i b r i u m p a r t i t i o n i n g c o n cepts and empirical measurements. Central to this approach is the use of a factor that a c c u r a t e l y p r e d i c t s fish/shellfish c o n t a m i n a n t levels. The BSAF is a scientifically defensible means of predicting fish tissue c o n t a m i n a n t concentrations based on levels in the sediment (8, 9). Selection of an a p p r o p r i a t e a n d conservative BSAF will r e q u i r e a critical review of the literature and sampling (fish and sediment) to determine whether a universally applicable BSAF can be developed or w h e t h e r site-specific indices must be considered. Fish a n d s e d i m e n t d a t a h a v e b e e n r e c o r d e d at sites throughout the country and could be used to initiate an evaluation of the consistency of the BSAF. Once a BSAF has been determ i n e d , sediment criteria could be calculated by substituting the BSAF for the BCF in EPA's standard risk equation. Site-specific parameters, if n e c e s s a r y to t h e c a l c u l a t i o n , could be further investigated to delineate the range of values that may exist. The resulting criterion established using the BSAF will be a sediment quality objective based on the protection of h u m a n health (aquatic life criteria c o u l d also be determ i n e d based on this methodological a p p r o a c h ) . C o m p l i a n c e w i t h this criterion could be determined by sampling surface sediments and d e t e r m i n i n g w h e t h e r dioxin samples are higher or lower than the S Q C . If c o m p l i a n c e w e r e to be based on an effluent dioxin limit, it w o u l d be necessary to d e v e l o p a pipe-to-sediment model. Conclusions and recommendations Dioxin is a s o l i d s c o n t a m i n a n t problem, which should be reflected in the development of criteria designed to protect h u m a n health and aquatic life. In this light, the appropriateness of developing water quality criteria for a strongly hydrophobic compound such as dioxin should be reassessed. BSAFs should be considered as a factor to be used to predict dioxin levels in fish tissue. Although limited existing data indicate that BSAFs are consistent, further work is needed, first, in evaluating the BSAF and sediment as predictors of dioxin fish tissue levels and, sec-
ond, in determining w h e t h e r SQC can be established by using a BSAF. The use of empirical data to establish dioxin SQC will avoid the problems encountered when improvements in analytical capabilities result in new compliance limits (e.g., dioxin water quality criteria). The application of an accepted risk equation, with slight modifications, should significantly facilitate the risk management process as it relates to dioxin SQC.
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Erik Rifkin is president of Rifkin and Associates, Inc., an environmental consulting firm in Columbia, MD. He has a Ph.D. in zoology from the University of Hawaii. He also had a National Academy of Sciences Postdoctoral Associateship at the Naval Medical Research Institute in Bethesda, MD. He has published a number of articles on the environmental fate of dioxin.
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Edward J. Bou wer is a professor of environmental engineering at the Johns Hopkins University. His research focuses on the transport and fate of organic contaminants in aquatic systems, especially biodégradation of hydrophobic chemicals and applications to in situ bioremediation. He has a Ph.D. from Stanford University.
References (1)
Mackay, D.; Shiu, W. Y.; Ma, K. C. Illustrated Handbook of PhysicalChemical Properties and Environmental Fate for Organic Chemicals; Lewis: Chelsea, MI, 1992, pp. 400-09. (2) Cook, P. M. et al. "Interim Report on Data and Methods for Assessment of 2,3,7,8-Tetrachlorodibenzo-p-dioxin Risks to Aquatic Life and Associated Wildlife"; Environmental Protection Agency: Washington, DC, 1993; EPA/ 600/R-93/055. (3) Ankley, G. T. et al. Can. J. Fish. Aquat. Sci. 1992, 49, 2080-85. (4) Carey, A. E.; Shifrin, N. S.; Cook, P. M. In Lake Ontario TCDD Bioaccumulation Study—Final Report; U.S. Environmental Protection Agency: New York, 1990; Chapter 9. (5) Batterman, A. R. et al. Chemosphere 1989, 19, 451-58. (6) Kuehl, D. W. et al. Chemosphere 1989, 16, 667-79. (7) Schell, J. D., Jr.; Campbell, D. M.; Lowe, E. Environ. Toxicol. Chem. 1993, 12, 2077-82. (8) Rifkin, E.; LaKind, J. /. Toxicol. Environ. Health 1991, 33, 103-12. (9) LaKind, J.; Rifkin, E. Environ. Sci. Technol. 1991, 24(7), 963-65.
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