Methods for aquatic ecological risk assessments of 2,3,7,8-TCDD and related chemicals
- Environmental Protection Agency, Duluth, MN (United States)
As part of USEPA`s ongoing assessment of the aquatic ecological risk of 2,3,7,8-TCDD and related polyhalogenated aromatic chemicals, available information on bioaccumulation and effects of these chemicals was analyzed to determine major uncertainties and approaches for addressing these uncertainties. Reported effects vary widely among chemicals, exposure conditions, and organisms. Considerable variability can be explained by relating effects to chemical accumulation, so measurement or prediction of chemical concentrations in tissues of aquatic organisms is essential in assessing risk. However, many of the most toxic of these compounds are difficult to measure in water and have uncertain activities based on available octanol-water partition coefficients. The biota-sediment accumulation factor (BSAF), through direct measurement of the fugacity gradient between sediments and organisms, can be used to predict bioaccumulation. When TCDD toxicity is expressed on the basis of accumulation, fish early-life-stage survival appears to be the most sensitive endpoint for aquatic organisms. For aquatic-associated wildlife, limited data requires that dose be referenced to TCDD concentration in food. Reproductive effects on certain fish-eating birds and mammals are of greatest concern. Such effect concentrations can be used to assess risk based on fish contamination surveys or, when combined with BSAFs and BAFs, on sediment and water concentrations. However, such assessments are made uncertain by limited toxicity information for certain taxonomic groups and endpoints.
- OSTI ID:
- 42904
- Report Number(s):
- CONF-9410273--
- Country of Publication:
- United States
- Language:
- English
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