ASTM E729-23e1

5.1?An acute toxicity test is conducted to obtain information concerning the immediate effects on test organisms of a short-term exposure to a test material under specific experimental conditions. An acute toxicity test does not provide information about whether delayed effects will occur, although a post-exposure observation period, with appropriate feeding, if necessary, might provide such information. Bioavailability of the test substance may also differ between real-world exposures and laboratory exposures due to site-specific water quality conditions (see Guides E1192, E1563, and E2455).

5.2?Results of acute toxicity tests might be used to predict acute effects likely to occur on aquatic organisms in field situations as a result of exposure under comparable conditions, except that (1) motile organisms might avoid exposure when possible, and (2) toxicity to benthic organisms might be dependent on sorption or settling of the test material onto the substrate.

5.3?Results of acute tests might be used to compare the acute sensitivities of different species and the acute toxicities of different test materials, and to study the effects of various environmental factors on results of such tests.

5.4?Results of acute toxicity tests might be an important consideration when assessing the hazards of materials to aquatic organisms (see Guide E1023) or when deriving water quality criteria for aquatic organisms 5.5?Results of acute toxicity tests might be useful for studying the biological availability of, and structure-activity relationships between, test materials.

5.6?Results of acute toxicity tests will depend on the temperature, composition of the dilution water, condition of the test organisms, exposure technique, and other factors.

1.1?This guide 1.2?Other modifications of these procedures might be justified by special needs or circumstances such as meeting specific study goals, regulatory needs, or to accommodate specific test organism life stages. Although using appropriate procedures is more important than following prescribed procedures, results of tests conducted using unusual or novel procedures are not likely to be comparable to results of many other tests. Comparison of results obtained using modified and unmodified versions of these procedures might provide useful information concerning new concepts and procedures for conducting acute tests.

1.3?This guide describes tests using three basic exposure techniques: static, renewal, and flow-through. Selection of the technique to use in a specific situation will depend on the needs of the investigator and on available resources. Tests using the static technique provide the most easily obtained measure of acute toxicity, but conditions often change substantially during static tests; therefore, static tests should not last longer than 96 h, and test organisms should not be fed during such tests unless the test organisms are severely stressed without feeding over 48 h. Static tests should probably not be conducted on materials that have a high oxygen demand, are highly volatile, are rapidly transformed biologically or chemically in aqueous solution, or are removed from test solutions in substantial quantities by the test chambers or organisms during the test. Because the pH and concentrations of dissolved oxygen and test material are maintained at desired levels and degradation and metabolic products are removed, tests using renewal and flow-through methods are preferable; test organisms may be fed during renewal and flow-through tests. Although renewal tests might be more cost-effective, flow-through tests are generally preferable.

1.4?Acute tests may be performed to meet regulatory data requirements or to obtain time-independent estimates of toxicity.