Radiological benchmarks for screening contaminants of potential concern for effects on aquatic biota at Oak Ridge National Laboratory, Oak Ridge, Tennessee

A hazardous waste site may contain hundreds of contaminants; therefore, it is important to screen contaminants of potential concern for the ecological risk assessment. Often this screening is done as part of a screening assessment, the purpose of which is to evaluate the available data, identify data gaps, and screen contaminants of potential concern. Screening may be accomplished by using a set of toxicological benchmarks. These benchmarks are helpful in determining whether contaminants warrant further assessment or are at a level that requires no further attention. Unlike exposures to chemicals, which are expressed as the concentration in water or sediment, exposures to radionuclides are expressed as the dose rate received by the organism. The recommended acceptable dose rate to natural populations of aquatic biota is 1 rad d{sup {minus}1}. Blaylock, Frank, and O`Neal provide formulas and exposure factors for estimating the dose rates to representative aquatic organisms. Those formulas were used herein to calculate the water and sediment concentrations that result in a total dose rate of 1 rad d{sup {minus}1} to fish for selected radionuclides. These radiological benchmarks are intended for use at the US Department of Energy`s (DOE`s) Oak Ridge Reservation and at the Portsmouth and Paducah gaseous diffusion plants as screening values only to show the nature and extent of contamination and identify the need for additional site-specific investigation