Environmental Risk Assessment Reports - Chapter 14

CHAPTER 14 Ecotoxicity Testing in Risk Assessment Guy L. Gilron and Ruth N. Hull CONTENTS I. Introduction.................................................................................................325 II. Ecotoxicity Testing: A Technical Review..................................................326 A. Basic Concepts .............................................................................326 B. Important Tools for Implementation............................................331 C. Current Issues and Uncertainties..................................................331 III. Consultant Selection........................................................................................333 A. Qualifications of Consultant.........................................................333 B. Quality System .............................................................................333 C. Accreditation and Certification ....................................................335 IV. Conclusion..................................................................................................335 References...................................................................................................337 I. INTRODUCTION* Toxicity tests are controlled laboratory experiments in which organisms are exposed to a contaminant (or contaminant mixture) for a specified duration, in order to evaluate potential toxic effects. The type of toxic effect measured depends upon the test organism exposed, the contaminant concentration, and the mechanism(s) of action. Acute lethality in test organisms is a commonly-measured response, since it is relatively straightforward to measure and is biologically meaningful. Examples * The authors wish to acknowledge Ms. E. Jonczyk (BEAK International, Inc.), and Mr. R. Scroggins (Method Development and Applications Section, Environment Canada) for their constructive and useful comments and suggestions on an earlier draft of this chapter. 325 © 2001 by CRC Press LLC 326 A PRACTICAL GUIDE TO ENVIRONMENTAL RISK ASSESSMENT REPORTS of acute tests are fathead minnow acute lethality (aquatic) and earthworm survival (terrestrial). Measurement of sublethal test responses are becoming more widely used and generally provide a more sensitive response. Sublethal test responses include changes in growth, reproduction, and behavior. Examples of sublethal tests are daphnid reproduction (aquatic) and radish seedling germination (terrestrial). Toxicity tests are used in both human health and ecological risk assessment, but in very different ways. In HHRA, data from mammalian toxicity tests are typically used to develop the RfDs and SFs that are used in the risk characterization phase to calculate risk. In ERA, ecotoxicity tests (nonmammalian) are conducted during the hazard/effects assessment phase, and become one of the lines of evidence for the risk characterization. Therefore, ecotoxicity tests are conducted during an ERA, but not during an HHRA. This primer will describe the use of toxicity tests for ERA only, since the HHRA RfDs and SFs are generally developed by the U.S. EPA; they are rarely generated on a site-specific basis. Toxicity test results are used in ERA to provide an indication of whether the contaminated media are toxic. The other lines of evidence (i.e., biological field surveys and chemical measurements of ambient media) provide information regarding the actual state of the environment (e.g., whether a fish community is typical of unim-pacted conditions) and which contaminants are likely to be responsible for observed toxic responses. However, only toxicity tests can directly evaluate whether the con-taminated media are toxic to biota. An impact observed in the field may be the result of natural conditions, rather than contaminants. Similarly, chemical concentrations in environmental media often provide little information regarding the bioavailability of contaminants to ecological receptors. Exposing test organisms to environmental media, under controlled laboratory conditions, provides this information. II. ECOTOXICITY TESTING: A TECHNICAL REVIEW Figure 1 illustrates a conceptual diagram which represents the framework of an ERA. The shaded box indicates where toxicity testing provides information in a risk assessment. A. Basic Concepts 1. Purpose of Conducting Ecotoxicity Tests Ecotoxicity tests are used to measure the combined biological effects of substances present in environmental samples on terrestrial and aquatic plants, animals, and microorganisms. Test organisms used in these tests have become standard because they are: · Generally representative of biota in soils, sediments, and water bodies · Are indicators of specific trophic levels in the ecosystem food web · Are easily maintained or cultured under laboratory conditions · Are generally sensitive to environmental contaminants © 2001 by CRC Press LLC ECOTOXICITY TESTING IN RISK ASSESSMENT 327 Figure 1 A conceptual diagram of the framework of an ecological risk assessment. Since different organisms (or trophic levels) vary in their sensitivities to toxi-cants, it is common practice, especially in the hazard assessment phases of an ERA, to apply a battery (i.e., three or more) of tests to provide an estimation of potential toxic effect(s) for contaminants or substances being assessed. 2. Procedures for Implementing Ecotoxicity Tests For a given test method, a predetermined number of organisms (e.g., 10) are exposed to each concentration in a dilution series (e.g., for effluent: 100%, 50%, 25%, 12.5%, 6.25%, etc.) of an environmental sample. The sample dilutions are prepared using “clean” dilution material (i.e., for terrestrial — silica sand; for aquatic — control/ dilution water). Alternately, test organisms can be exposed to both 100% of an “impacted” site medium and 100% of a “reference” site medium; in this case, no dilutions would be required. At the end of the exposure period, the measured biological response of the test organisms is determined and usually expressed quan-titatively as a statistically-derived toxicity endpoint (e.g., lethality, decreased repro-duction, growth inhibition). 3. Exposure Duration There are generally two major categories of toxicity tests with regard to exposure duration. Tests are either acute or chronic. Acute tests cause an effect within a short period in relation to the life span of the test organisms, while chronic tests cause effects which occur during a relatively long-term period of exposure, usually a significant portion of the life span of the organism (e.g., > 10% of its life cycle). © 2001 by CRC Press LLC 328 A PRACTICAL GUIDE TO ENVIRONMENTAL RISK ASSESSMENT REPORTS Acute tests (usually measuring lethality) are the most common type of toxicity test, and are used predominantly in regulatory testing. Chronic tests (those measuring sublethal responses, such as growth and reproduction inhibition) are becoming more common in environmental impact and risk assessments, and yield more information regarding the variety of biological effects of contaminant materials. 4. Test Endpoints Determined from Ecotoxicity Tests The response of test organisms exposed to each concentration of sample is graph-ically plotted or statistically analyzed in order to estimate the concentration of the sample that produces a level or degree of response. For example, the most widely-used endpoint (in acute tests) is the LC50, which is the concentration of the sample that would cause lethality in 50% of the test organisms during the exposure duration. Other endpoints, such as the no-observed-effect-concentration (NOEC), the lowest-observed-effect-concentration (LOEC), and the inhibition concentration (e.g., IC50) are typical sublethal/chronic endpoints. The endpoints appropriate to the test method utilized are usually calculated using various computer programs (e.g., TOXSTAT). 5. Quality Assurance/Quality Control Program In consideration of the high priority of ecotoxicity information in environmental risk decision-making, it is crucial that ecotoxicity data be of the highest possible quality. Therefore, a rigorous and comprehensive QA/QC program should be established in the laboratory conducting the tests. This program should comprise a number of important components, which include the following: a. Standard Operating Procedures (SOPs) Recognizing the necessity of standardized procedures for all aspects of laboratory operations, a full range of SOPs should be established; these SOPs are dated and an ongoing schedule of review (at least semiannually) is implemented with these SOPs. SOPs should be written for all laboratory-related procedures including: test methods; equipment calibration and maintenance; test organism care and culturing; procedures for handling, treatment, and storage of samples and reagents; and clean-ing procedures for test chambers. All SOPs are updated whenever a significant deviation from conventional practice has been implemented to improve the perfor-mance or efficiency of the methods. b. Testing Procedures Specified methods for each ecotoxicity test should be on hand for reference in the testing lab. Recognized, published international, federal, provincial, state, and other agency test methods are used as appropriate (e.g., ASTM, U.S. EPA, Environment Canada, ISO, OECD). A list of examples of ecotoxicity test methods used in ERA is provided in Table 1. © 2001 by CRC Press LLC ECOTOXICITY TESTING IN RISK ASSESSMENT 329 Table 1 Examples of Ecotoxicity Test Methods Used in Ecological Risk Assessment Taxon Freshwater Fish Invertebrates Algae Marine Fish Invertebrates Algae Freshwater Sediment Invertebrates Soil Test Species Rainbow trout Fathead minnow Daphnia magna Ceriodaphnia dubia Selenastrum capricornutum Duckweed Inland silverside Sheepshead minnow Threespine stickleback Sea urchin/Sand dollar Amphipod Mussel Skeletonema costatum Champia parvula Hyalella sp. _Chironomus sp. Earthworm Eisenia sp. Test Methods* OECD, ASTM, US EPA, EC OECD, ASTM, US EPA, EC OECD, ASTM, US EPA, EC OECD, ASTM, US EPA, EC ASTM, US EPA, EC APHA US EPA US EPA EC US EPA, EC US EPA, EC ASTM US EPA US EPA ASTM, US EPA, EC ASTM, US EPA, EC OECD, US EPA OECD, US EPA Note: APHA = American Public Health Association ASTM = American Society for Testing Materials EC = Environment Canada OECD = Organization for Economic Cooperation and Development US EPA= U.S. Environmental Protection Agency Individual bench sheets for recording chemical and biological data should be provided for each test, and originals should be stored in a central file. Bench sheets document date of sample receipt, date of test initiation, chemical and physical exposure conditions, name of test technician(s) monitoring tests, test observations, and comments identifying unusual observations or deviations from the SOP. © 2001 by CRC Press LLC ... - tailieumienphi.vn