Derivation of aquatic screening benchmarks for 1,2-dibromoethane.

Ethylene dibromide (1,2-dibromoethane or EDB) was primarily used in the United States as an additive in leaded gasoline and as a soil and grain fumigant for worm and insect control until it was banned in 1983. Historical releases of EDB have resulted in detectable EDB in groundwater and drinking wells, and recently concentrations up to 16 microg/L were detected in ground water at two fuel spill plumes in the vicinity of the Massachusetts Military Reservation Base on Cape Cod, Massachusetts. Because the ground water in this area is used to flood cranberry bogs for the purposes of harvesting, the U.S. Air Force sponsored the development of aquatic screening benchmarks for EDB. Acute toxicity tests with Pimephales promelas (fathead minnow), Daphnia magna, and Ceriodaphnia dubia were conducted to provide data needed for development of screening benchmarks. Using a closed test-system to prevent volatilization of EDB, the 48-h LC50S (concentration that kills 50% of the test organisms) for P. promelas, D. magna, and C. dubia were 4.3 mg/L, 6.5 mg/L, and 3.6 mg/L, respectively. The screening benchmark for aquatic organisms, derived as the Tier II chronic water quality criteria, is 0.031 mg EDB/L. The sediment screening benchmark, based on equilibrium partitioning, is 2.45 mg EDB/kg of organic carbon in the sediment. The screening benchmarks developed here are an important component of an ecological risk assessment, during which perhaps hundreds of chemicals must be evaluated for their potential to cause ecological harm.