Toxicity evaluation testing procedures

Also, the test procedure (protocol) is fundamental because it allows comparing results from different laboratories and from different experimental sets. Moreover, selected test protocol could affect the interpretation of the results, the information content and its application in the safety evaluation process, as stated by Frazer if the biological system is exposed to a test chemical for 24 h and the endpoint assay is immediately conducted, the data produced would be most relevant to the acute toxicity of the test material. If, on the other hand, the system is exposed to material for 24 h and the system is cultured in the absence of the test material for additional 48 h before the endpoint assay is conducted, the data would be more relevant to recovery from toxicity rather than acute toxicity [7]. 

Toxicity. The fourth characteristic that could make a waste a hazardous waste is toxicity (40 CFR 261.24). To determine if a waste is a toxic hazardous waste, a representative sample of the material must be subjected to a test conducted in a certified laboratory using a test procedure [toxicity characteristic leaching procedure, (TCLP)]. Under federal rules (40 CFR 261), all generators are required to use the toxicity characteristic leaching procedure test when evaluating wastes. 

Kwan, K.K. Dutka, B.J. Evaluation of the Toxi-Chromotest direct sediment toxicity testing procedure and Microtox sohd-phase testing procedure. B. Environ. Contam. Tox. 1992, 49, 656 662. 

The third health effect bioassay employed utilizes acute toxicity in whole animals (rats). Since the major objective of the Level 1 biological testing procedure is to identify toxicology problems at minimal cost, a two-step approach is taken to the initial acute in vivo toxicology evaluation of unknown compounds. The first is based on a... 

The solidified SSM sample at the optimum reagent ratio was tested for metal leachability by the Toxic Characteristic Leaching Procedure as per 51 FR 21685-21693.(7) The target metals were analyzed by atomic absorption spectrometer using USEPA SW-846 "Test Methods for Evaluating Solid Wastes," 1986(8) as required by 40 CFR Part 261.( ... 

The enormous cost of multiple-species, multiple-dose, lifetime evaluations of chronic effects has already made the task of carrying out hazard assessments of all chemicals in commercial use impossible. At the same time, quantitative structure activity relationship (QSAR) studies are not yet predictive enough to indicate which chemicals should be so tested and which chemicals need not be tested. In exposure assessment, continued development of analytical methods will permit ever more sensitive and selective determinations of toxicants in food and the environment, as well as the effects of chemical mixtures and the potential for interactions that affect the ultimate expression of toxicity. Developments in QSARs, in short-term tests based on the expected mechanism of toxic action and simplification of chronic testing procedures, will all be necessary if the chemicals to which the public and the environment are exposed are to be assessed adequately for their potential to cause harm. 

Guzzella, L. (1998) Comparison of test procedures for sediment toxicity evaluation with Vibrio fischeri bacteria, Chemosphere 37 (14-15), 2895-2909. 

Evaluation of a series of effluents using different acute and chronic toxicity test procedures. 

KW Brown and KC Donnelly Texas A M University Develop a comprehensive laboratory testing procedure for evaluating the acute and chronic toxicity of complex environmental mixtures ... 

The test report must include all information necessary to provide a complete and accurate description of the test procedures and an evaluation of the results. It should contain a summary of the data, an analysis of the data, and the conclusions drawn from the analysis. The summary must highlight data or observations and any deviations from control data which are indicative of toxic effects. 

Computers are now used in the design and development of new chemicals, and their employment in toxicity prediction could lead to improved products that present a reduced hazard to humans. Although computers are useful for performing routine calculations, they do not usually possess insight or rationalization. Therefore, they should represent only one of a number of test procedures used to formulate a full safety evaluation in a given chemical. Where they are used, their results should be interpreted by a panel of expert toxicologists capable of providing an overall view of the likely toxic risk in the human environment. 

These metals are considered hazardous under the Resource Recovery and Conservation Act of 1987 (RCRA) [4]. The RCRA metals occur in chemical forms that are soluble or insoluble in groundwater. The soluble species are of concern from the dispersibility viewpoint. Hence, the test criterion to evaluate whether a given waste stream needs stabilization prior to disposal is based on how much a given hazardous metal dissolves in water in a standardized test. This EPA test, called the Toxicity Characteristic Leaching Procedure (TCLP) [5], is used not only to identify which waste streams need treatment, but also to assess whether the treated waste form is suitable for disposal. This test also sets limits on how little of a hazardous metal is permitted to leach out from a given waste to pass the waste for disposal. If the test determines that the waste is not suitable for safe... 

Toxicity test procedure in higher animals (e.g., rats, mice, rabbits, dogs, and monkeys) is different from that in lower animals because the number of available animals usually is limited. As mentioned earlier, it is not economical or practical to use a few hundred mammals for the evaluation of a single toxicity test. The limitation in number has necessitated several adjustments to assure the validity of toxicity determinations in higher animals. Typically, in the pesticide industry, three types of tests are required acute, subacute, and chronic. 

Environmental contaminants are present as complex mixtures, so that if toxicity is found, procedures known as toxicity identification evaluation may be carried out. This procedure identifies toxic components by systematically treating the effluent, elutrate, or pore water to remove various fractions - hydro-phobic ( fat soluble ) chemicals, metals, acids, volatile compounds, etc. - and retesting the toxicity after each extraction. Loss of toxicity after an extraction implicates the chemical that was extracted. This is confirmed by chemical analysis and toxicity tests on... 

Third, many times the toxicity tests are selected on the basis of cost, and this is a valid parameter. A FIFRA mesocosm may cost as much as 750,000 compared to as little as 500 for a D. magna acute toxicity test. The danger is from both ends of the spectrum. The more expensive multispecies test is not necessarily better unless it answers specific questions left unanswered by the simpler tests. In fact, the large multispecies tests are performed only after a thorough review and evaluation of simpler testing procedures. Likewise, the simpler and less costly toxicity tests may not adequately address the fate and effects of a xenobiotic, leaving a great deal of uncertainty in the prediction of environmental effects. 

U.S. EPA (1992). Toxicity characteristic leaching procedure (Method 1311). In Test Methods for Evaluating Solid Waste, Physical/Chemical Methods, Office of Solid Waste, U.S. Enviromnental Protection Agency, Washington, DC. 

This Is a compilation of articles from WEFJournals and 1992 conference. The 20 articles cover testing methods, toxicity reduction evaluations, policy, industrial effluent tests, test procedures, and false positives. 

The philosophical approach of Japanese chemical control seems to be somewhat different to the rest of the developed world. For example, the fundamental aim of the MITI/MHW notification scheme [14] is to evaluate the potential human hazard from exposure to new chemicals through the environment. Therefore a stepwise testing procedure is adopted, and the ecotoxicity and toxicity studies may have to be conducted... 

For applications in the rain trap system, the results of the EPA s toxicity characterization leaching procedure (TCLP) indicate that none of the tire products tested exceeds proposed TCLP regulatory levels. Most compounds detected are found at trace levels, (near method detection limits), from 10 to 100 times less than TCLP regulatory limits and U.S. EPA drinking water standard maximum contaminant level (MCL) values. The Florida Department of Environmental Regulation released its final report on tire teachability in potential usage environments. The study, which evaluates the leachability of shredded tires in different aquatic environments, finds that scrap tires pose no harmful effects when used in applications that are above the water table [14]. 

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