Human and Ecological Risk Assessment - Earthjustice

Appendix HEcological BenchmarksStep 3: Calculate BenchmarksThe following equation provided the basis for calculating surface water benchmarksusing a population-inference benchmark (e.g., endpoint on fecundity).Benchmark I fish BAF Cw Iw Cwbw(H-2)whereI fish = intake of contaminated fish (kg/d)BAF = whole-body bioaccumulation factor (L/kg)bw = weight of the representative species (kg)I w = intake of contaminated water (L/d)C w = total concentration in the water (mg/L).For chemicals that bioaccumulate significantly in fish tissue, the ingestion ofcontaminated food tends to dominate the exposure (i.e., [I fish × C fish ] >> [I w C w ]), and the waterterm (i.e., [I w × C w ]) can be dropped from Equation H-2, resulting in Equation H-3:BenchmarkIfish BAF Cw (H-3)bwAt the benchmark dose (mg/kg/d), the concentration in water is equivalent to the chemicalstressor concentration limit for that receptor as a function of body weight, ingestion rate, and thebioaccumulation potential for the chemical of concern. Hence, Equation H-3 can be rewritten tosolve for the surface water (CSCL sw ) as follows:CSCLswbenchmark bw (H-4)I I BAFwfishH.2 Ecological BenchmarksThe ecological benchmarks used to calculate ecological HQs in the CCW risk assessmentare summarized in Table H-3, which provides the constituent name; the criterion and receptorfor sediment and aquatic receptors; and the source for each benchmark.April 2010–Draft EPA document. H-5