Standard Test Method for Measuring the Toxicity of Sediment-Associated Contaminants with Estuarine and Marine Invertebrates

Importancia y uso:

5.1 General: 

5.1.1 Sediment provides habitat for many aquatic organisms and is a major repository for many of the more persistent chemicals that are introduced into surface waters. In the aquatic environment, most anthropogenic chemicals and waste materials including toxic organic and inorganic chemicals eventually accumulate in sediment. Mounting evidences exists of environmental degradation in areas where USEPA Water Quality Criteria (WQC; Stephan et al.(66)) are not exceeded, yet organisms in or near sediments are adversely affected Chapman, 1989 (67). The WQC were developed to protect organisms in the water column and were not directed toward protecting organisms in sediment. Concentrations of contaminants in sediment may be several orders of magnitude higher than in the overlying water; however, whole sediment concentrations have not been strongly correlated to bioavailability Burton, 1991 (68). Partitioning or sorption of a compound between water and sediment may depend on many factors including: aqueous solubility, pH, redox, affinity for sediment organic carbon and dissolved organic carbon, grain size of the sediment, sediment mineral constituents (oxides of iron, manganese, and aluminum), and the quantity of acid volatile sulfides in sediment Di Toro et al. 1991(69) Giesy et al. 1988 (70). Although certain chemicals are highly sorbed to sediment, these compounds may still be available to the biota. Chemicals in sediments may be directly toxic to aquatic life or can be a source of chemicals for bioaccumulation in the food chain.

5.1.2 The objective of a sediment test is to determine whether chemicals in sediment are harmful to or are bioaccumulated by benthic organisms. The tests can be used to measure interactive toxic effects of complex chemical mixtures in sediment. Furthermore, knowledge of specific pathways of interactions among sediments and test organisms is not necessary to conduct the tests Kemp et al. 1988, (71). Sediment tests can be used to: (1) determine the relationship between toxic effects and bioavailability, (2) investigate interactions among chemicals, (3) compare the sensitivities of different organisms, (4) determine spatial and temporal distribution of contamination, (5) evaluate hazards of dredged material, (6) measure toxicity as part of product licensing or safety testing, (7) rank areas for clean up, and (8) estimate the effectiveness of remediation or management practices.

5.1.3 A variety of methods have been developed for assessing the toxicity of chemicals in sediments using amphipods, midges, polychaetes, oligochaetes, mayflies, or cladocerans (Test Method E1706, Guide E1525, Guide E1850; Annex A1, Annex A2; USEPA, 2000 (72), EPA 1994b, (73), Environment Canada 1997a, (74), Enviroment Canada 1997b,(75)). Several endpoints are suggested in these methods to measure potential effects of contaminants in sediment including survival, growth, behavior, or reproduction; however, survival of test organisms in 10-day exposures is the endpoint most commonly reported. These short-term exposures that only measure effects on survival can be used to identify high levels of contamination in sediments, but may not be able to identify moderate levels of contamination in sediments (USEPA USEPA, 2000 (72); Sibley et al.1996, (76); Sibley et al.1997a, (77); Sibley et al.1997b, (78); Benoit et al.1997, (79); Ingersoll et al.1998, (80)). Sublethal endpoints in sediment tests might also prove to be better estimates of responses of benthic communities to contaminants in the field, Kembel et al. 1994 (81). Insufficient information is available to determine if the long-term test conducted with Leptocheirus plumulosus (Annex A2) is more sensitive than 10-d toxicity tests conducted with this or other species.

5.1.3.1 The decision to conduct short-term or long-term toxicity tests depends on the goal of the assessment. In some instances, sufficient information may be gained by measuring sublethal endpoints in 10-day tests. In other instances, the 10-day tests could be used to screen samples for toxicity before long-term tests are conducted. While the long-term tests are needed to determine direct effects on reproduction, measurement of growth in these toxicity tests may serve as an indirect estimate of reproductive effects of contaminants associated with sediments (Annex A1).

5.1.3.2 Use of sublethal endpoints for assessment of contaminant risk is not unique to toxicity testing with sediments. Numerous regulatory programs require the use of sublethal endpoints in the decision-making process (Pittinger and Adams, 1997, (82)) including: (1) Water Quality Criteria (and State Standards); (2) National Pollution Discharge Elimination System (NPDES) effluent monitoring (including chemical-specific limits and sublethal endpoints in toxicity tests); (3) Federal Insecticide, Rodenticide and Fungicide Act (FIFRA) and the Toxic Substances Control Act (TSCA, tiered assessment includes several sublethal endpoints with fish and aquatic invertebrates); (4) Superfund (Comprehensive Environmental Responses, Compensation and Liability Act; CERCLA); (5) Organization of Economic Cooperation and Development (OECD, sublethal toxicity testing with fish and invertebrates); (6) European Economic Community (EC, sublethal toxicity testing with fish and invertebrates); and (7) the Paris Commission (behavioral endpoints).

5.1.4 Results of toxicity tests on sediments spiked at different concentrations of chemicals can be used to establish cause and effect relationships between chemicals and biological responses. Results of toxicity tests with test materials spiked into sediments at different concentrations may be reported in terms of an LC50 (median lethal concentration), an EC50 (median effect concentration), an IC50 (inhibition concentration), or as a NOEC (no observed effect concentration) or LOEC (lowest observed effect concentration). However, spiked sediment may not be representative of chemicals associated with sediment in the field. Mixing time Stemmer et al. 1990b, (83), aging ( Landrum et al. 1989, (84), Word et al. 1987, (85), Landrum et al., 1992,(86)), and the chemical form of the material can affect responses of test organisms in spiked sediment tests.

5.1.5 Evaluating effect concentrations for chemicals in sediment requires knowledge of factors controlling their bioavailability. Similar concentrations of a chemical in units of mass of chemical per mass of sediment dry weight often exhibit a range in toxicity in different sediments Di Toro et al. 1990, (87) Di Toro et al. 1991,(69). Effect concentrations of chemicals in sediment have been correlated to interstitial water concentrations, and effect concentrations in interstitial water are often similar to effect concentrations in water-only exposures. The bioavailability of nonionic organic compounds in sediment is often inversely correlated with the organic carbon concentration. Whatever the route of exposure, these correlations of effect concentrations to interstitial water concentrations indicate that predicted or measured concentrations in interstitial water can be used to quantify the exposure concentration to an organism. Therefore, information on partitioning of chemicals between solid and liquid phases of sediment is useful for establishing effect concentrations Di Toro et al. 1991, (69).

5.1.6 Field surveys can be designed to provide either a qualitative reconnaissance of the distribution of sediment contamination or a quantitative statistical comparison of contamination among sites.

5.1.7 Surveys of sediment toxicity are usually part of more comprehensive analyses of biological, chemical, geological, and hydrographic data. Statistical correlations may be improved and sampling costs may be reduced if subsamples are taken simultaneously for sediment tests, chemical analyses, and benthic community structure.

5.1.8 Table 2 lists several approaches the USEPA has considered for the assessment of sediment quality USEPA, 1992, (88). These approaches include: (1) equilibrium partitioning, (2) tissue residues, (3) interstitial water toxicity, (4) whole-sediment toxicity and sediment-spiking tests, (5) benthic community structure, (6) effect ranges (for example, effect range median, ERM), and (7) sediment quality triad (see USEPA, 1989a, 1990a, 1990b and 1992b, (89, 90, 91, 92 and Wenning and Ingersoll (2002 (93)) for a critique of these methods). The sediment assessment approaches listed in Table 2 can be classified as numeric (for example, equilibrium partitioning), descriptive (for example, whole-sediment toxicity tests), or a combination of numeric and descriptive approaches (for example, ERM, USEPA, 1992c, (94). Numeric methods can be used to derive chemical-specific sediment quality guidelines (SQGs). Descriptive methods such as toxicity tests with field-collected sediment cannot be used alone to develop numerical SQGs for individual chemicals. Although each approach can be used to make site-specific decisions, no one single approach can adequately address sediment quality. Overall, an integration of several methods using the weight of evidence is the most desirable approach for assessing the effects of contaminants associated with sediment, (Long et al. 1991(95) MacDonald et al. 1996 (96) Ingersoll et al. 1996 (97) Ingersoll et al. 1997 (98), Wenning and Ingersoll 2002 (93)). Hazard evaluations integrating data from laboratory exposures, chemical analyses, and benthic community assessments (the sediment quality triad) provide strong complementary evidence of the degree of pollution-induced degradation in aquatic communities (Burton, 1991 (68), Chapman 1992, 1997 (99, 100).)

5.2 Regulatory Applications—Test Method E1706 provides information on the regulatory applications of sediment toxicity tests.

5.3 Performance-based Criteria: 

5.3.1 The USEPA Environmental Monitoring Management Council (EMMC) recommended the use of performance-based methods in developing standards, (Williams, 1993 (101). Performance-based methods were defined by EMMC as a monitoring approach which permits the use of appropriate methods that meet preestablished demonstrated performance standards (11.2).

5.3.2 The USEPA Office of Water, Office of Science and Technology, and Office of Research and Development held a workshop to provide an opportunity for experts in the field of sediment toxicology and staff from the USEPA Regional and Headquarters Program offices to discuss the development of standard freshwater, estuarine, and marine sediment testing procedures (USEPA, 1992a, 1994a (88, 102)). Workgroup participants arrived at a consensus on several culturing and testing methods. In developing guidance for culturing test organisms to be included in the USEPA methods manual for sediment tests, it was agreed that no one method should be required to culture organisms. However, the consensus at the workshop was that success of a test depends on the health of the cultures. Therefore, having healthy test organisms of known quality and age for testing was determined to be the key consideration relative to culturing methods. A performance-based criteria approach was selected in USEPA, 2000 (72) as the preferred method through which individual laboratories could use unique culturing methods rather than requiring use of one culturing method.

5.3.3 This standard recommends the use of performance-based criteria to allow each laboratory to optimize culture methods and minimize effects of test organism health on the reliability and comparability of test results. See Annex A1 and Annex A2 for a listing of performance criteria for culturing or testing.

Subcomité:

E50.47

Referida por:

E0724-21, E1391-03R23, E2122-22, E2591-22, E2455-25, E1850-04R19, E1688-19, E1611-21, E1706-25, E1525-02R23, E1563-21A, E3163-24, E1562-22

Volúmen:

11.09

Número ICS:

07.060 (Geology. Meteorology. Hydrology)

Palabras clave:

Ampelisca abdita; amphipod; bioavailability; chronic; Eohaustorius estuarius; estuarine; invertebrates; Leptocheirus plumulosus; marine; Rhepoxynius abronius; sediment; toxicity;