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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 7019

Roger B. Yeardley, Jr., James M. Lazorchak, and Michael A. Pence; Evaluation of Alternative Reference Toxicants for Use in the Earthworm Toxicity Test. Environmental Toxicology & Chemistry 14(7):1189-1194, 1995

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The use of the 14-day earthworm toxicity test to aid in the evaluation of the ecological impact of contaminated soils is becoming increasingly widespread. However, the method is in need of further standardization. As part of this continuing process, the choice of reference toxicants was evaluated. Reference toxicants were rated in relation to the following criteria: (a) reproducibility, (b) low human health hazard, (c) feasibility of measurement, and (d) chemical stability. Potassium chloride (KCl) and ammonium chloride (NH4Cl) were evaluated as possible alternatives to the one currently in common use, 2-chloroacetamide. Potassium chloride rated the best for the combination of the four criteria, followed by NH4Cl and 2-chloroacetamide. Coefficients of variation (C.V.s) from control charts of six definitive tests were used to measure reproducibility. The best reproducibility (lowest C.V.) was shown by KCl, followed by NH4Cl and 2-chloroacetamide. Toxicants ranked KCl < NH4Cl << 2-chloroacetamide in terms of health hazard; and KCl = NH4Cl > 2-chloroacetamide in terms of measurement feasibility. Both 2-chloroacetamide and NH4Cl changed in concentration during testing. Evidence is also presented that 2-chloroacetamide degrades rapidly during testing, and that, as dead worms decay, ammonification may be adding another toxicant, ammonia, to tests.