Aquatic toxicity test methods

Small-scale toxicity tests are numerous and their relative merits (and limitations) for undertaking environmental assessment have been amply documented (Wells et ah, 1998 Persoone et ah, 2000). The small-scale toxicity tests methods described in this book and the hazard assessment schemes into which they can be incorporated are certainly representative of the field of small-scale aquatic toxicology and of tests and approaches being applied actively in today s world. 

Test method standardization (TMS) calls for several actions that involve 1) preparation of a formal draft test method document for each bioassay intended for standardization, 2) a critical review by an expert subcommittee, 3) the preparation of a final draft test method, 4) an international peer review of each test method, 5) an inter-calibration exercise of the final draft test method, 6) finalization of each test method and 7) the formal publication of the toxicity test method document. Environment Canada (EC) has been particularly active in biological test method standardization and has thus far contributed 18 standardized aquatic and sediment... 

CANMET (1997a) Review of methods for sublethal aquatic toxicity tests relevant to the Canadian metalmining industry, Aquatic Effects Technology Evaluation (AETE) Program, Project 1.2.1, Canada Centre for Mineral and Energy Technology (CANMET), Mining Association of Canada (MAC), Ottawa, Ontario, pp. 1-132. 

Rue, W.J., Fava, J.A. and Grothe, D.R. (1988) A review of inter- and intralaboratory effluent toxicity test method variability, in M.S. Adams, G.A. Chapman and W.G. Landis (eds.), Aquatic Toxicology and Hazard Assessment l(fh Volume, ASTM STP 971, American Society for Testing and Materials,... 

Toxic effects of all classes of contaminants including metals, pesticides, and organic substances can be captured with the pT-method, as long as the test battery employed reflects a sufficiently wide spectrum of sensitivity. Furthermore, test organisms in a battery should be representative of aquatic biota. The composition of test batteries can be varied according to different aquatic environments and country-specific issues. Clearly, application of the pT-method is suitable for several experimental designs which are linked to toxicity testing (methods, test species, endpoints). 

The pT-method can also be applied to assess liquids (untreated and treated wastewater, surface waters and groundwater). All data from aquatic toxicity tests used to detect pollutants can be integrated into this method. A general description of the pT-method is given in Chapter 3 of this volume. The present chapter specifically addresses the application of the pT-method to sediments and dredged material in order to classify and categorize the hazard associated with the degree of contamination of these matrices. 

The relationship being found between endocrine system, the nervous system, and immune system will make these endpoints prime areas for further development of chronic toxicity test methods for aquatic organisms and should be considered for ecological and hazard risk assessments of chemicals [7,386]. 

Many test methods are available for aquatic toxicity testing (Table 1). They differ in cost, precision, complexity, and the skill needed to conduct them. Nevertheless, their objectives are similar. They are conducted to determine the relative potency among chemicals and the relative susceptibility among different species and life stages and to identify other variables that influence the overall outcome of exposure. Toxicity tests are usually conducted to meet regulatory guidelines for the use and discharge of... 

We have seen that variability in toxicity testing can arise from repeat measurements made within a laboratory and also between laboratories. In reality, the variability seen between laboratories is a consequence of both within- and be-tween-laboratory sources of variability, and both are also subject to the within-test variability referred to earlier, as evident from differences between test replicates. Research based on a series of acute aquatic toxicity tests (Whitehouse el al., 1996) shows that variation between laboratories is higher than that between repeat tests in the same laboratory. This, in turn, accounts for more variability than that seen between replicates within a test. Similar findings are evident from the work of others in connection with the introduction of whole-effluent toxicity tests in the USA (e.g. Warren-Hicks and Parkhurst, 1992 Fulk, 1995). Over the years, a number of authors have examined variability in aquatic toxicity testing. Typically these describe variability in terms of the coefficient of variation (standard deviation divided by the mean) in EC50 or LC50 values that is achieved when the same toxicant is tested several times (or by several laboratories) using the same method. Table 2.3 summarises the results of a review of published data. 

The OECD Daphnia spp acute immobilisation and reproduction tests. A mainstay in aquatic toxicity testing, Daphnia tests have been used also to evaluate the toxicity of contaminated groundwaters and leachates (Kross and Cherryholmes, 1992). As with any of the aquatic tests, the principal problem with the Daphnia test is the need to extract a suitable aqueous sample. This problem is illustrated by Kross and Cherryholmes (1992), who compared D. magna and Microtox assay results in leachates but found a poor correlation between the two methods. 

Van der Kooij, L.A., Van de Meent, D., VanLeeuwen, C.J., Bruggeman, W.A., 1991. Deriving quality criteria for water and sediment from the results of aquatic toxicity tests and product standards application of the equilibrium partitioning method. Water Res. 25, 697-705. 

Results from this extensive effects testing demonstrates that PDMS has a relatively low toxicity to freshwater, marine and terrestrial organisms. As a result, in most cases no dose/response relationships or toxicity differences between species exist. The toxicity test methods that most realistically simulate PDMS exposure in the environment produce the most reliable measure of potential PDMS environmental effects. For example, sediment-bound PDMS will be the primary route of exposure in the aquatic environment, because PDMS has not been measured in overlying water (due to its negligible water solubility and potential for sorption onto sediments). Therefore, studies in which PDMS was dosed as a component of sediment are the most realistic exposure... 

There is a discrepancy between the cyanide criteria for both aquatic and drinking water standards and the current analytical technology. The criteria are stated for free cyanide (which Includes hydrocyanic acid and the cyanide ion), but the EPA approved analytical methodology for total cyanide measures the free and combined forms (11). This test probably overestimates the potential toxicity. An alternative method (cyanides amenable to chlorination) measures those cyanide complexes which are readily dissociated, but does not measure the iron cyanide complexes which dissociate in sunlight. This method probably tends to underestimate the potential toxicity. Other methods have been proposed, but similar problems exist (12). The Department of Ecology used the EPA-approved APHA procedure which includes a distillation step for the quantification of total cyanide (13,14). A modification of the procedure which omits the distillation step was used for estimation of free cyanide. Later in the study, the Company used a microdiffusion method for free cyanide (15). 

Phipps, G.L. and G.W. Holcombe. 1985. A method for aquatic multiple species toxicant testing acute toxicity of 10 chemicals to 5 vertebrates and 2 invertebrates. Environ. Pollut. 38A 1,41-157. 

Since the publication of the third edition, additional data have been critically reviewed. New or additional data included in this edition are bioconcentration factors, aquatic mammalian toxicity values, degradation rates, corresponding half-lives in various environmental compartments, ionization potentials, aqueous solubility of miscellaneous compounds, Henry s law constants, biological, chemical, and theoretical oxygen demand values for various organic compounds. Five additional tables have been added Test Method Number Index, Dielectric Values of Earth Materials and Fluids, Lowest Odor Threshold Concentrations of Organic Compoimds in Water, and Lowest Threshold Concentrations of Organic Compounds in Water. 

As protozoa and nematodes live in pore water in the soil, most of the methods are adapted from toxicity tests designed for aquatic samples. Among the protozoa the tests with cihates Tetrahymena pyriformis, Tetrahymena thermophiia, Colpoda cucullus, Colpoda inflata, Colpoda steinii, Paramecium caudatum, and Paramecium aurelia have been developed [ 102,112-117]. It is the opinion of some authors that the sensitivity of infusorians is higher than that of microorganisms [115,116]. 

Interpretation of the biological significance of residue levels fonnd in wildhfe Adoption of improved uniform methods of quantitation so that residne levels can be compared, and so that a time estimate of their environmental significance can be made (NRCC 1975 USEPA 1988) Reexamination of aquatic toxicity data wherein concentrations tested exceeded the solubihty of chlordane in water of 6 to 9 pg/L (WHO 1984)... 

U.S. Environmental Protection Agency, Committee on Methods for Toxicity Tests with Aquatic Organisms. 1975. Methods for acute toxicity tests with fish, macroinvertebrates, and amphibians. 

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