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Bioavailability refers to the extent to which humans and ecological receptors are exposed to contaminants in soil or sediment. The concept of bioavailability has recently piqued the interest of the hazardous waste industry as an important consideration in deciding how much waste to clean up. The rationale is that if contaminants in soil and sediment are not bioavailable, then more contaminant mass can be left in place without creating additional risk. A new NRC report notes that the potential for the consideration of bioavailability to influence decision-making is greatest where certain chemical, environmental, and regulatory factors align. The current use of bioavailability in risk assessment and hazardous waste cleanup regulations is demystified, and acceptable tools and models for bioavailability assessment are discussed and ranked according to seven criteria. Finally, the intimate link between bioavailability and bioremediation is explored. The report concludes with suggestions for moving bioavailability forward in the regulatory arena for both soil and sediment cleanup.
The fiscal and technological limitations associated with cleaning up hazardous waste sites to background conditions have prompted responsible parties to turn to risk-based methods for environmental rememdiation. Environmental Cleanup at Navy Facilities reviews and critiques risk-based methods, including those developed by the U.S. Environmental Protection Agency and the American Society of Testing and Materials. These critiques lead to the identification of eleven criteria that must be part of any risk-based methodology adopted by the Navy, a responsible party with a large number of complex and heavily contaminated waste sites. January
The U.S. Environmental Protection Agency is developing Ecological Soil Screening Level (Eco-SSL) benchmarks for ecological risk assessment of contaminants at Superfund sites. Benchmarks for invertebrates Were developed from existing literature. Insufficient information for Ba, Be, Mn, and Sb to generate Eco-SSLs necessitated standardized toxicity testing to fill the data gaps. We used the Enchytraeid Reproduction Test (ERT) with Enchytraeus crypticus in this study. This test was selected on the bases of its ability to measure chemical toxicity to ecologically relevant test species during chronic assay, and its inclusion of at least one reproductive component among the measurement endpoints. Tests were conducted in Sassafras sandy loam soil, which supports relatively high bioavailability of metals. Aging/weathering procedures for amended treatment soil were incorporated into the study to better reflect the "real world" exposure conditions. The toxicity order based on juvenile production was Be> Mn> Sb> Ba with EC20 values of 45, 116, 194, and 585 mg kg-1, respectively. These results show that ERT is a robust and sensitive assay for toxicity assessments and is appropriate for the Eco-SSL development.
Proceedings of the Fifth International FZK/TNO Conference on Contaminated Soil, 30 October-3 November, 1995, Maastricht, the Netherlands