Toxicity classification

Toxicity classification is based on recommended exposure limits provided by chemical suppliers. This rating is provisional and will be reviewed when toxicological testing is completed. 

TABLE 5.2. Comparison of Toxicity Classification Based on LD50 versus Fixed Dose Procedure... 

Toxicity Classification Based on LD5o Fixed-dose Number of Laboratories Classifying Chemical ... 

NH Air Res. Div. 1998. Toxic air pollutants With toxicity classifications and ambient air limits. New Hampshre Air Resources Division, State Department of Environmental Services. NH Code Admin. R. Ann. Env-A 1300,1400. 

Strorrkhorst J, Bowner C., Guchte van de C., Hurk van den P, Schipper C. and Vonck W., Toxicity classification of marine harbour sediment. SETAC Europe annual meeting 1996, Taormina, Italy. 

All of the top nine cotton pesticides in California are labeled by the U.S. Environmental Protection Agency as Category I or Category II materials, the most toxic classifications. 

Persoone, G., Marsalek, B., Blinova, I., Tordkne, A., Zarina, D., Manusadzianas, L., Nalecz-Jawecki, G., Tofan, L., Stepanova, N., Tothova, L. and Kolar, B. (2003) A practical and user-friendly toxicity classification system with microbiotests for natural waters and wastewaters, Environmental Toxicology 18 (6), 395-402. 

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). 

A toxicity classification system for wastes discharged into the aquatic environment... 

Toxicity Classification System for Effluents Discharged into the Aquatic Environment According to Persoone101... 

Persoone, G., B. Marsalek, I. Blinova, et al. 2003. A practical and user-friendly toxicity classification system with microbiotests for natural waters and wastewaters. Environ. Toxicol. 18 395-402. 

Holmes E, Nicholls AW, Lindon JC, Connor SC, Connelly JC, Haselden JN, Damment SJP, Spraul M, Neidig P, Nicholson JK. Chemometric models for toxicity classification based on NMR spectra of biofluids. Chem Res Toxicol 2000 13 471 178. 

Table 7.2 presents a toxicity classification system based upon an LD50 single oral dose in rats. In applying this system to the drugs listed in Table 7.1 we can see that these drugs would be classified from almost nontoxic to highly toxic. However, it must be emphasized that caution should be exercised when using such classification systems to communicate risk information. 

The cut-off values for classification of mixtures are normally specified by concentrations expressed as % of the component substance. In some cases, for example acute toxicity (human health), the cut-off values are expressed as acute toxicity values (ATE). The classification of a mixture is determined by additivity calculation based on acute toxicity values (see Chapter 3.1) and concentrations of component substances. Similarly acute aquatic toxicity classification may be calculated on the basis of acute aquatic toxicity values (see Chapter 4.10) and where appropriate, corrosion/irritation by adding up concentrations of individual substances (see Chapters 3.2 and 3.3). Component substances are taken into consideration for application of the formula when the concentration is equal to or greater than 1 %. Some competent authorities (CA) may use this cut-off as a basis of obligation to compile an SDS. 

If a mixture is diluted with a substance that has an equivalent or lower toxicity classification than the least toxic original ingredient, and which is not expected to affect the toxicity of other ingredients, then the new mixture may be classified as equivalent to the original mixture. Alternatively, the formula explained in paragraph 3.1.3.6.1 could be applied. 

Captafol is a general use pesticide with a toxicity classification of IV (relatively nontoxic). It is classified a as restricted use pesticide in the United States. It is no longer sold in the United States. The Occupational Safety and Health Administration threshold limit value for captafol is reported to be 0.1 mgm . ... 

The prediction of activity, agonism versus antagonism, adds an additional layer of complexity to the problem of toxicity classification of compounds. 

The principle of the toxicity classification system for wastes discharged into the aquatic environment is a two-step determination and quantification of the acute toxicity of the liquid wastes or leachates with the battery of bioassays. In the first step the toxicity is determined on non-diluted samples, and in the second step the toxicity tests are performed on a dilution series of the samples with all bioassays for which more than 50% effect has been found in the non-diluted sample. 

Judson, R. R, Elloumi, F., Setzer, R. W., Li, Z., and Shah, I. A. (2008). A comparison of machine learning algorithms for chemical toxicity classification using a simulated multi-scale data model. BMC Bioinform 9, 241—256. 

However, it is obvious that the FDA approach is a generalized toxicity classification and cannot supply the answers to questions such as, what are the metabolites and which compounds will be teratogens, mutagens or oncogens. Although the FDA approach has built its foundation on a broad data base, it does not narrow its spectrum to a precise toxicological response or mode of action. 

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