Toxicity tests classification

The importance of hydrolysis potential, ie, whether moisture or water is present, is illustrated by the following example. In the normal dermal toxicity test, namely dry product on dry animal skin, sodium borohydride was found to be nontoxic under the classification of the Federal Hazardous Substances Act. Furthermore, it was not a skin sensitizer. But on moist skin, severe irritation and bums resulted. 

Rousseeuw [4]. Massart and Kaufman [5] and Bratchell [6] wrote specifically for chemometricians. Massart and Kaufman s book contains many examples, relevant to chemometrics, including the meteorite example [7]. More recent examples concern classification, for instance according to structural descriptions for toxicity testing [8] or in connection with combinatorial chemistry [9], according to chemical... 

Figure 1 Classification of toxicity tests in environmental toxicology.

A Guidance Document on Acute Inhalation Toxicity Testing is being developed and presently exists as a draft (OECD 2004b). The document recommends the Acute Toxic Class (ATC) Method with a group size of three animals per sex, if the objective of the test is solely related to hazard classification. Limits for particle-size distribution of aerosolized test substances are suggested. The preferred mode of exposure is the nose-only, head-only, or head/nose-only exposure technique, because this mode of exposure minimizes exposure or uptake by noninhalation routes. 

Due to the specificity of toxicogenomic signatures, compounds may be classified based on common genes (or pathways) disrupted. In developmental toxicity testing, approaches may be used for classification between (1) toxic and nontoxic exposures and/or (2) classes of chemical compounds. To date, most classification studies have been conducted in alternative developmental systems (i.e. stem cells, zebrafish, whole embryo culture) due to the size of material and experimental groups needed. In a series of studies by... 

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. 

Table 6. Point allocation scheme for sample ranking and hazard classification based on a toxicity test core battery [HAS 1].

Hazard potential for each effluent was calculated using a mathematical formula (the PEEP index) proposed by Costan et al. (1993). This formula integrates the ecotoxic responses of the battery of tests before and after a biodegradation step. Toxicity test endpoint responses are first transformed to toxic units. The product of effluent toxicity and effluent flow (m3/h) gives the toxic loading value. The log 10 value of an effluent s toxic loading corresponds to its PEEP index. In order to rank the effluents a toxicity classification scale is generated (Tab. 11). 

Lamberson, J.O. and Swartz, R.C. (1992) Spiked-sediment toxicity test approach, in Sediment Classification Compendium, EPA 823-R-92-006, U.S. EPA, Office ofWater, Washington, DC. 

The general objective, principle, and scope of application of the pT-method are succinctly described in Section 1 and also reported elsewhere in this book (see Chapter 3 of this volume, Section 5.1), where readers will appreciate that this hazard assessment scheme is adaptable to both liquid and solid media. Briefly recalled here in the context of solid-media samples such as dredged material, the pT-value, which relates to a single bioassay, and the pT-index, derived from the most sensitive organism in a test battery, permit a numerical classification of environmental samples on the basis of ecotoxicological principles. Sediment from any aquatic ecosystem (freshwater, brackish, marine) and from any of its phases (whole sediment, porewaters, elutriates or organic extracts) can be appraised provided that the proper standardized toxicity tests are available. There are whole-sediment test protocols standardized for many agencies (e.g., Environment Canada, ASTM). 

Classification of mixtures where acute toxicity test data are available for the complete mixture... 

Aquatic toxicity testing, by its nature, involves the dissolution of the substance under test in the water media used and the maintenance of a stable bioavailable exposure concentration over the course of the test. Some substances are difficult to test under standard procedures and thus special guidance will be developed on data interpretation for these substances and how the data should be used when applying the classification criteria. 

When there is acute toxicity test data (LC50 or EC50) available for the mixture as a whole, this data as well as information with respect to the classification of components for chronic toxicity should be used to complete the classification for tested mixtures as follows. When chronic (long-term) toxicity data (NOEC) is also available, this should be used as well. 

This section addresses the use of acute and chronic toxicity data in classification, and special considerations for exposure regimes, algal toxicity testing, and use of QSARs. For a more detailed discussion of aquatic toxicity concepts, one can refer to Rand (1996). 

However where classification is applied solely due to the acute toxicity (L(E)C5o) observed in single algae/aquatic plant tests, but there is evidence from a range of other algae tests that the chronic toxicity (NOECs) for this taxonomic group is above lmg/1, this evidence could be used to consider declassification. At present this approach cannot be applied to aquatic plants since no standardized chronic toxicity tests have been developed. 

Hydrolytically unstable Maintaining exposure concentrations. Toxicity of breakdown products. Comparison of degradation half-lives to the exposure regimen used in testing. Classification requires expert judgement, should be based on measured concentrations, and needs to address the toxicity of significant breakdown products. 

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