KWRRI Research Reports


Aquatic toxicity tests were conducted on 11 organic compounds considered hazardous to water resources. The toxicity of each compound was evaluated using embryo-larval stages of two to eight fish and amphibian species. Exposure was initiated at fertilization and maintained through 4 days posthatching. The animal test species exhibited varying degrees of sensitivity to the selected toxicants. Combined frequencies for mortality and teratogenesis at 4 days posthatching gave LC50 ranges of 3.66 to 8.25 mg/L for benzene, 1.16 to 22.42 mg/L for carbon tetrachloride, 0.11 to 1.20 mg/L for chlorobenzene, 2.03 to > 68 mg/L for chloroform, 3.01 to 5.56 mg/L for 1,2-dichlorobenzene, 2.54 to .34 mg/L for 1,2-dichloroethane, 13.16 to > 48 mg/L for methylene chloride, 0.002 to 0.64 mg/L for nitrobenzene, 0.04 to .32 mg/L for phenol, 0.02 to 0.85 mg/L for toluene, and 3.53 to 3.77 mg/L for m-xylene. The species which exhibited the greatest susceptibility to organic compounds were the rainbow trout, Rana pipiens, and Rana temporaria. The more sensitive amphibian species generally were those which normaly are restricted to aquatic or moist terrestrial habitats, whereas the more tolerant amphibians included those semi-aquatic and terrestrial species which appear to be more broadly adapted ecologically. Of the 11 test compounds, nitrobenzene, toluene, chlorobenzene, and phenol were the most toxic. The least toxic organics included dichloroethane and methylene chloride. For three chlorinated alkanes, including methylene chloride (CH2Cl2), chloroform (CHCl3), and carbon tetrachloride (CCl4), toxicity was found to 1ncrease with the degree of chlorination. Concerning several aromatic hydrocarbons, benzene always was found to be less toxic than its monosubstituted analogs. Toxicity of the 11 compounds was further evaluated by calculating toxicant concentrations which produced embryo-larval mortality and/or teratogenesis at frequencies of 10% (LC10) and 1% (LC1). The LC values, used to estimate toxicity thresholds, ranged from < 0.l for nitrobenzene to 69.9 μg/L for methylene chloride. A limited number of toxicity tests were performed to determine whether embryo-larval bioassays are suitable to assess effects of transitory chemical exposures, such as those resulting from intermittent discharges or accidental spills of chemicals into water resources. Results indicated that Rana pipiens embryos were sufficiently sensitive to quantify effects produced by short-term exposures to chloroform. Animals tested during the earliest embryonic stage appeared to be less tolerant than organisms exposed later in development.

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The work upon which this report is based was supported in part by funds provided by the Office of Water Research and Technology, United States Department of the Interior, Washington, D.C., as authorized by the Water Research and Development Act of 1978. Public Law 95-467.