Laboratory toxicity tests

Baughman, D.S., D.W. Moore, and G.I. Scott. 1989. A comparison and evaluation of field and laboratory toxicity tests with fenvalerate on an estuarine crustacean. Environ. Toxicol. Chem. 8 417-429. 

Similarly, the reductions in toxicity observed in laboratory toxicity tests where exposure is modified (either through the addition of sediment or by removal to clean water) are also apparent in the field. Field effect concentrations are generally observed to occur at concentrations around three to ten times above those based on standard laboratory data. Dissipation and degradation are therefore clearly the critical factors in mitigating effects of pyrethroids under field conditions. This provides reassurance that preliminary ecological risk assessments based on... 

Persoone, G. Janssen, C.R. Field validation of predictions based on laboratory toxicity tests. In Freshwater Field Tests for Hazard Assessment of Chemicals Hill, I.A., Helmbach, F., Leeuwangh, P., Matthiessen, P., Eds. CRC Press, Inc. Boca Raton, EL, 1994 379-397. 

Laboratory toxicity tests have been developed and conducted over the past decades to demonstrate adverse effects that chemicals can have on biological systems. Along with other complementary tools of ecotoxicology available to measure (potential or real) effects on aquatic biota (e.g., microcosm, mesocosm and field study approaches with assessment of a variety of structural and/or functional parameters), they have been, and continue to be, useful to indicate exposure-effect relationships of toxicants under defined, controlled and reproducible conditions (Adams, 2003). 

Our scrutiny of publications identified in the literature search has enabled us to uncover the various ways in which laboratory toxicity tests have been applied, many of which are small-scale in nature. We have assembled papers based on their application affinities and classified them into specific sections, as shown in Figure 1. This classification scheme essentially comprises the structure of this chapter and each section is subsequently commented hereafter. 

Rossi, D. and Beltrami, M. (1998) Sediment ecological risk assessment in situ and laboratory toxicity testing of Lake Orta sediments, Chemosphere 37 (14-15), 2885-2894. 

The use of laboratory toxicity tests to monitor industrial effluent discharges has become a common approach to estimating the potential for environmental effects in North America and Europe. Numerous schemes have been developed to characterize and assess potential toxic effects in aquatic receiving environments. The first regulatory application of Environmental Effects Monitoring (EEM) in Canada was within the 1992 Pulp and Paper Liquid Effluent Regulations, promulgated under the Fisheries Act. A second application of EEM in Canada was within the 2002 Metal... 

Sublethal toxicity tests that use species of relatively low sensitivity (z. e., fathead minnow) reduce the usefulness of both EEM Hazard Assessment Schemes to estimate potential effects observed in the field. Insensitive laboratory measurements can lead to an underestimation of potential field effects and reduce the strength of laboratory toxicity tests as good estimators of effects. 

Another noteworthy limitation of the SED-TOX index, which is actually a limitation of toxicity bioassays, relates to the fact that results measured in toxicity tests only provide a measure of what is occurring under very specific laboratory test conditions, and an indication of what is or could occur in the field. To maximize the ecological relevance of the laboratory toxicity tests, there is a need to relate the SED-TOX scores with a series of benthic community matrices. 

Use of several laboratory toxicity tests (at least two), usually representative of different levels of biological organization (e.g., a battery composed of a bacterial, algal, microinvertebrate and fish test) to attempt to circumscribe the full toxicity potential of a liquid or solid matrix sample. Volume 2(1,8). 

Adequate extrapolation of results from standard laboratory toxicity tests to other time scales of exposure and response requires observations on the time course of toxic effects. These observations can then be used to construct time-to-event models, such as the DEBtox model mentioned above. These models explicitly address both intensity and duration of exposure to hazardous chemicals, and better use is made of the data gathered from toxicity experiments. Diverse endpoints in time can be addressed, and individual organism characteristics and/or environmental circumstances (e.g., temperature) can be incorporated as covariables. An overview of time-to-event models and approaches and their use in the risk assessment of chemicals is provided by Crane et al. (2002). 

Life history models may be useful for considering age- or stage-specific variability in sensitivity in the extrapolation of response however, it should not be assumed that smaller or younger stages are always the most sensitive. The few studies that have addressed the impact of time of year on responses of aquatic communities to a stressor indicate that, in freshwater communities, threshold concentrations for direct toxic effects vary within a factor of 2 among seasons — well within the normal range of variation observed in laboratory toxicity tests. However, at greater exposures, the intensity and duration of direct and indirect responses may vary considerably between different periods of the year because of the influence of climatic and seasonal factors on recovery. 

Risk is generally considered as a product of the probability of an adverse effect and the magnitude of that effect. In ecotoxicology, risk depends on the probability and intensity of exposure and the sensitivity of the exposed organisms, whereby the interpretation of risk can involve aspects of space and time and value judgments (e.g., believing that 1 species is more important than another). The sensitivity is often determined in laboratory toxicity tests, in which dose- or concentration-effect curves are established. Extrapolation methods exist for both components of risk and the additional aspects. 

Ecological risk assessment of chemical mixtures may be conducted using the same types of data sources and approaches as in human risk assessment of mixtures. Available data and approaches are, however, different in kind and numbers. The vast majority of data are from laboratory toxicity tests with mostly binary mixtures... 

Contaminated media that are collected for laboratory toxicity tests may include contaminated water, soil, or sediment (the mud at the bottom of lakes, rivers, streams, bays, etc.), or extracts of these media. Organisms used for conducting soil toxicity tests... 

Sources of data that might be used in the construction of stressor-response functions include the results of toxicity tests (lethal, chronic) performed under controlled laboratory conditions, direct measures of exposure and response in controlled field experiments, and the application of statistical relationships that estimate the biological effects of chemicals based on physical or chemical properties of specific toxicants. The order of preference among these sources of data lists field observations as the most valuable, followed by laboratory toxicity tests, and finally by the use of empirical relationships. In the absence of directly relevant data, the development of stressor-response functions may require the use of extrapolations among similar stressors or ecological effects for which data are available. For example, effects might have to be extrapolated from the available test species to an untested species of concern in an ERA. Similarly, toxicity data might be available only for a chemical similar to the specific chemical stressor of concern in an ERA, and thereby require an extrapolation from one chemical to another to perform the assessment. 

The results of the traditional acute single-species toxicity tests conducted in the laboratory cannot be used alone to predict effects on natural populations, communities, and ecosystems. The cultural species in laboratory tests are different from those in most ecosystems. Conditions such as the size of the test species, its life stage, and nutritional state can have an effect on toxicity. Furthermore, the experimental conditions in laboratory tests cannot duplicate the complex interacting physical and chemical conditions of ecosystems, such as seasonal changes in water temperature, dissolved oxygen, and suspended solids. In addition to these environmental modifying factors, aquatic life is usually exposed simultaneously to numerous potential toxicants (mixtures). Although the toxicities of binary and ternary mixtures have been evaluated for some chemicals in laboratory toxicity tests, the resultant information has predictive limitations. 

Cairns Jr., J. (1986) What is meant by validation of predictions based on laboratory toxicity tests Hydrobiologia, 137, 271-278. 

Direct measurement of effects on biota, rather than inferring these from comparisons of residue data and the results of laboratory toxicity tests. 

Lloyd (1973) carried out laboratory toxicity tests using a selection of candidate pyrethroids on T. ctistaneum and susceptible anti resistant S. grants riusm. The results were bioresmethrin > resmethrin > bioallethrin > allethrin > tetra-methrin, When synergized with PBO the same pattern emerged. The results are shown in Table 16.4. 

This book focuses on the development, application, and analysis of a methodology for forecasting probable effects of toxic chemicals in the production dynamics of aquatic ecosystems. Topics include extrapolation of laboratory toxicity tests, effects of toxins, forecasting toxic effects, laboratory and outdoor pond experiments, and modeling. 

In ecological effects assessment, there are many problems involved, eg, it is often observed that laboratory test data over estimate more commonly than underestimate toxicity, because laboratory toxicity tests are conducted in filtered water of low suspended solids eg, soil particles) and low organic matter content, which play an important role in natural environments. Therefore, test methods including multi-species and simulating environmental conditions, ie, more sophisticated ecosystems or field test methods should be developed for determination of more reliable assessment factors (AFs), in spite of its difficulties. It will be necessary to develop both aquatic toxicology methods and terrestrial or sediment ecotoxicology. 

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