Published: Jan 1993
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In response to testing recommendations of the TSCA Interagency Testing Committee (ITC) and as of December 31, 1988, the U.S. Environmental Protection Agency (EPA) had published 182 Federal Register (FR) notices under Section 4 of the Toxic Substances Control Act (TSCA) to implement the ITC's chemical fate, health effects, ecological effects and bioconcentration testing recommendations. The types and numbers of these FR notices were previously described as were the notices, chemicals, tests and methods related to chemical fate testing (Walker, 1990a). This paper describes the FR notices requesting the ecological effects and bioconcentration testing recommended by the ITC, the types and numbers of chemicals for which this testing was requested and received, the types and numbers of tests that were requested and received, and the methods that were used to conduct those tests. As of December 31, 1988, the EPA had responded to the ITC's testing recommendations by publishing 24 TSCA Section 4 FR notices requesting 299 ecological effects and 10 bioconcentration tests for 42 chemicals. Most of the ecological effects (234) and bioconcentration (6) tests that were conducted by using 51 different methods had been received by December 31, 1988.
Methods for testing chemicals with Henry's Law Constant a ⩾10−2 atm m3/mole should be modified. Bioconcentration methods should be modified to develop more reliable data, if there is a valid need for this information. Toxicity test methods for algae should be modified to develop exact EC50 values, taking into consideration that closing the algal test system to prevent evaporation of the test chemical can limit CO2 availability. An insufficient number of chemicals with Henry's Law Constant a ⩾10−2 atm mVmole were tested to determine if the methods for aquatic vertebrate and fish can produce exact LC50, values. However, based on this limited testing, exact aquatic invertebrate and fish LC50 values can be produced for chemicals with Henry's Law Constants a ⩾10−3 atm m3/mole.
Methods for testing chemicals with water solubilities ⩽1mg/L should be modified. Bio-concentration test methods should be modified so that the lengths of the uptake and depuration phases are inversely proportional to water solubility. Toxicity test methods for algae, aquatic invertebrates and fish should be modified to include the use of carrier solvents, solvent controls and extended exposure periods, if exact EC50 or LC50values are needed. Preliminary flow-through tests using one concentration of chemical-saturated test water should be conducted to determine if any adverse effects are produced. If adverse effects are produced, then definitive test should be conducted.
Bioconcentration test methods should be modified to include multiple chemical concentrations and toxicity measurements to establish any correlations between body burdens and toxicity (Walker, 1990c). Algal bioassays should include measurements of photosynthesis/respiration ratios. Methods for measuring the acute toxicity of chemicals to oysters should be modified to improve growth of control oysters.
Efforts should be made to harmonize bioconcentration or ecological test methods between organizations, states or countries. These efforts should not compromise the integrity or sacrifice the quality of an individual method, but should strive to identify common parts of different methods that can be cost-effectively harmonized and should acknowledge that some methods may not be totally harmonious. Harmonization efforts should recognize that the ability of some methods to produce reliable data is limited by the physical and chemical properties of the test substance. These limitations should be carefully articulated or used as the basis for modifying methods to eliminate these limitations.
Interagency Testing Committee, ecological effects, bioconcentration, Toxic Substances Control Act
Executive Director, TSCA Interagency Testing Committee (TS-792), U.S. Environmental Protection Agency, Washington, DC,
Paper ID: STP19236S