Test organisms

One of the most crucial aspects of a toxicity test is the suitability and health of the test organisms or, in the case of multispecies toxicity tests, the introduced community. It is also important to define clearly the goals of the toxicity test. If the protection of a particular economic resource such as a salmon fishery is of overriding importance, it may be important to use a salmonid and its food sources as test species. Toxicity tests are performed to gain an overall picture of the toxicity of a compound to a variety of species. Therefore the laboratory test species is taken only as representative of a particular class or, in many cases, phyla. 

Some of the criteria for choosing a test species for use in a toxicity test are listed and discussed below. 

The test organism should be widely available through laboratory culture, procurement from a hatchery or other culture facility, or collection from the field. In many cases marine organisms are difficult to culture successfully in the laboratory environment requiring field collection. 

The organism should be successfully maintained in the laboratory environment and available in sufficient quantities. Many species do not fare well in the laboratory our lack of knowledge of the exact nutritional requirements, overcrowding, and stress induced by the mere presence of laboratory personnel often make certain species unsuitable for toxicity testing. 

The relative sensitivities to various classes of toxicants of the test species should be known relative to the endpoints to be measured. This criterion is not often realized in environmental toxicology. The invertebrate Daphnia magna is one of the most commonly used organisms in aquatic toxicology, yet only the results for approximately 500 compounds are listed in the published literature. The fathead minnow has been the subject of a concerted test program at the U.S. EPA Environmental Research Laboratory—Duluth, conducted by G. Vieth, yet fewer than a thousand compounds have been examined. In contrast the acute toxicity of over 2000 compounds has been examined using the Norway rat as the test species. 

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Value is LD q = lethal dose low, ie, lowest dose of a substance iatroduced by any route other than inhalation, adrninistered over any given period of time ia a single or divided dosage that has been reported to have caused death in the test organism. 

Fire and Wind Hazards. Weather resistance of roof covetings is not necessarily correlated to fire and wiad resistance. Underwriters Laboratory and the Factory Mutual System test and rate fire and wiad hazard resistance, and some durabiUty tests. Organic felt or fiber glass mat base shingles are commonly manufactured to meet minimum UL requirements, which, ia addition to minimum mass, require wiad and fire resistance properties. 

Hospital sterilizer loads vary in composition, thus the challenge presented to the test organism can vary considerably, depending on the type and contents of packages in which they are placed. The benefits of a standardized test-pack constmction and test protocol are obvious, and such recommendation is made by AAMI for steam and ethylene oxide sterilizers (11). More recentiy in European (CEN) and International (ISO) standards, biological indicators are considered as additional information supplemental to the measurement of physical parameters. Indeed, for sterilization using moist heat (steam), the biological indicator information is not considered to be relevant. 

As with many of the vitamins, biological assays have an important historical role and are widely used. For example, microbiological assays use l ctobacillusplantarum ATCC No. 8014 (57,59) or l ctobacillus arabinosus (60). These methods are appropriate for both nicotinamide and nicotinic acid. Selective detection of nictonic acid is possible if l euconostoc mesenteroides ATCC No. 9135 is used as the test organism (61). The use of microbiological assays have been reviewed (62). 

For most assays, the incorporated pantothenic acid has to be Hberated en2ymatically. Usually, a combination of pantotheinase and alkaline phosphatase is used to hberate the bound pantothenic acid. The official method for pantothenic acid of the Association of Official Analytical Chemists (AOAC) is the microbiological assay that uses U. Plantarium (A.TCC 8014) as the test organism (71). Samples are extracted at 121°C at pH 5.6—5.7, proteins are precipitated at pH 4.5, and the resulting clear extracts are adjusted to pH 6.8 prior to assay. This procedure is only suitable to determine calcium pantothenate or other free forms of pantothenic acid. 

Aquatic toxicity is becoming (ca 1997) a permit requirement on all discharges. Aquatic toxicity is generally reported as an LC q (the percentage of wastewater which causes the death of 50% of the test organisms in a specified period ie, 48 or 96 h, or as a no observed effect level (NOEL), in which the NOEL is the highest effluent concentration at which no unacceptable effect will occur, even at continuous exposure. 

A relatively small number of studies have reported on the effects of cumene on plants, fish, and other organisms. Studies of the effects of cumene on fresh and saltwater fish indicate the lowest reported toxic concentration (LC q) for fishes was 20 to 30 mg/L (18). The solubiUty of cumene is about 50 mg/L (19). Among invertebrates, the lowest reported concentration that was toxic to test organisms was 0.012 mg/L after 18 hours (20). The only available data on the effect of cumene on aquatic plants indicate that the photosynthesis of several species was inhibited at concentrations from 9 to 21 mg/L (19). 

Disinfection tests can be classified according to the test organism, ie, whether the test employs certain species of bacteria, fungi, or vimses classified as to whether it is a static test or a cidal test, as in a bactericidal vs bacteriostatic test or sporicidal vs sporistatic test or classified as to whether it is a microbial reduction test or an end-point test where all the organisms in the test are apparently killed. Procedures may be distinguished by in vitro or in vivo testing. Another way to consider tests is whether they are screening tests, practical type laboratory tests, or field tests. 

Some tests of the AO AC (309,310) are Hsted in Table 10. The phenol coefficient test employs three test organisms and a standard concentration of... 

Name Type Test organisms Resistance standard... 

Further it is planned to use tests - organisms of various trophie levels to eaiTy out systematie reseai ehes on eompaiison of results of an estimation of quality of natural waters to the help of the different generalized pai ameters. 

LD5f (median lethal dose) A standard measure of toxicity indicating the dose of a substance that will kill 50% of a group of test organisms. 

All wiring and electrical equipment in chemical plants should be installed in accordance with the National Electrical Code. Electrical equipment for use in hazardous locations should be recognized by Underwriters Laboratories (or other testing organizations recognized by the authority having jurisdiction) for the conditions to be encountered. 

F. Feigl, Spot Tests, Organic Applications. Vol. II, p. 296. Elsevier, Amsterdam, 1954. 

The mysid shrimp, Mysidopsis bahia, is the test organism for the liquid and suspended particulate phases. This species has been shown to be exceptionally sensitive to toxic substances and is considered to be a representative marine organism for bioassay testing by EPA. An LCj, is determined the suspended particulate phase (SPP) bioassay tests. 

Toxicity Bioassay. Ninety-six hour acute toxicity tests were conducted on the effluent streams of major industries. A static renewal procedure was used in which waste waters of various dilutions were renewed at 24 hour intervals over a 96 hour period. Rainbow trout was used as the test organism. Tests were conducted at 13°C in 20 liter aquaria according to standard procedures (22), Results are summarized in Table 8. Chemical and toxicity test results indicate that the trace element quantities identified in Table 8 are not acutely toxic under the prevailing conditions and unlikely to pose an acute threat to aquatic life. In this case a chronic toxicity assessment would require additional research. 

They may be subdivided into phenol coefficient-type tests, of which there are many, quantitative suspension tests (which measure the rate at which test organisms are killed) and tests carried out at use-dilutions. 

The test organism may be placed on the skin, e.g. on the back of the hand, and the preparation to be evaluated placed on the same area. After a given time interval the area is swabbed with sterile cotton wool and the swab incubated in a suitable medium or washed in a suitable fluid, and viable counts are subsequently made. 

Graded doses ofthe test substance are incorporated into broth dispensed in McCartney boules and the bottles inoculated with the test organism and incubated. The point at which no growth occurs is taken as the bacteriostatic concentration (minimum inhibitory concentration, MIC). It is essential when performing these tests to determine the size of the inoculum as the position of the end-point varies considerably with inoculum size, which should always be defined in any description of result. 

The solution is placed in contaet with agar, which is already inoculated with the test organism and after ineubation zones of inhibition observed. The solution may be placed in a small eup sealed to the agar surfaee (a method used widely in anhbiotic assays) in a well cut from the agar with a sterile cork-borer, or applied in the form of an inpregnated disc of filter paper (Fig. 11.5 A). 

A number of tests have been deseribed which imitate, at least in part, the principle of the phenol eoeffieient test for liquid disinfectants. A culture of the test organism is mixed intimately with the semi-sohd preparation, and the mixture subcultuied by means of a loop into a suitable broth designed to disperse the base and neutrahze the antibacterial activity of the medicament. 

It is possible to also test semi-solid antibacterial preparations on the skin itself, as described for liquid disinfectants (section 3.5.1). A portion of the skin— the backs of the fingers between the joints is a useful spot— is treated with the test organism, the preparation is then applied and after a suitable interval the area is swabbed and the swab incubated in a suitable medium. Alternatively, the method employing pig skin, described in section 3.5.1, may well be adapted to the problem of testing semi-solid skin disinfectants. 

Solid disinfectants may be evaluated in vitro by applying them to suitable test organisms growing on solid medium. Discs may be cut from the agar and subcultured, observing the usual precautions. 

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