Toxicity tests, biological

Biological toxicity tests are widely used for evaluating the toxicants contained in the waste. Most toxicity bioassays have been developed for liquid waste. Applications of bioassays in wastewater treatment plants fall into four categories [19]. The first category involves the use of bioassays to monitor the toxicity of wastewaters at various points in the collection system, the major goal being the protection of biological treatment processes from toxicant action. 

Ahtiainen, J., Nakari, T. and Silvonen, J. (1996) Toxicity of TCF and ECF pulp bleaching effluents assessed by biological toxicity tests, in M.R. Servos, K.R. Munkittrick, J.Ef. Carey and G.J. Van Der Kraak (eds.), Environmental Fate and Effects of Pulp and Paper Mill Effluents, St-Lucie Press, FL, pp. 33-40. 

EinaHy, the ecotoxicological studies, designed to assess the impact of the substance on the environment, embrace acute toxicity tests to fish and Daphnia, and a battery of tests for the biodegradabiUty of the substance and its biological oxygen demand characteristics. 

Biological sui veys should be used together with whole-effluent and ambient toxicity testing, and chemical-specific analyses to assess the attainment/nonattainment of designated aquatic hfe uses in state water-quahty standards. ... 

Porewater Toxicity Testing Biological, Chemical, and Ecological Considerations Carr and Nipper, editors 2003... 

Toxicology and environmental health studies often lack a firm foundation of baseline data, and the NASGLP is a perfect starting point for a baseline data survey. During the field component of the survey, the crews collected two composite samples. One represented the top 5 cm of the soil directly below the litter layer (which will include a lot of the airborne components if they are present), and a second came from the 0-30-cm interval, independent of which soil horizon this may represent. Within this interval (the active layer), most of the interactions between biota and the non-living soil components take place, and thus is the important interval for this type if study. Environment Canada s Biological Methods Division selected one of the northern New Brunswick sites to collect a bulk sample in an attempt to create reference sites across Canada for standardized toxicity test methods. 

Toxicity tests are necessary tools to evaluate the concentration and duration of exposure of a chemical required to produce certain adverse effects. Molecular processes directly affected by the exposure to the chemical agent are the most liable criterions. Nevertheless, these effects are difficult to detect in aquatic toxicology because the processes are generally not well understood [72], Alternatively, other end points which fulfil the necessary requirements, namely the need to be unequivocal, relevant, easy to observe, describe and measure, biologically significant and repeatable, are used. These include measures of mortality, which is frequently employed in the early evaluation of the toxicity of a pollutant in acute toxicity tests. This criterion allows comparison of toxicity exerted by chemical agents with very different mechanisms of action. 

Before this topic is left behind, it should be noted that statistical significance is by no means the only consideration in interpretation of toxicity test results. If, in our particular case, the pathologist were to inform us that the brain lesion observed was extremely unusual or rare, we should certainly hesitate to dismiss our concerns because of lack of statistical significance. The toxicologist needs equally to understand biological significance, and, in this case, would almost certainly pursue other lines of investigation (perhaps an ADME study to determine if the pesticide reaches the brain, or a toxicity test in other species) to determine whether the effect was truly caused by the chemical. 

The biological approach (whole effluent) to toxics control for the protection of aquatic life involves the use of acute and chronic toxicity tests to measure the toxicity of wastewaters. Whole effluent tests (WET) employ the use of standardized, surrogate freshwater or marine (depending on the mixture of effluent and receiving water) plants (algae), invertebrates, and vertebrates. 

Preference is obviously for a simple chemical assay for PSP. Unfortunately the more specific the chemical test, the narrower is the window of compounds it can assay. The Paralytic Shellfish Poison is not just Saxitoxin (STX) as originally believed, but is a mixture of compounds closely related to STX Q) and the mix varies widely with location and with time ( ). It would seem, therefore that a chemical assay should determine at least the ratios of the several compounds, and that the relative toxicity of each of the compounds must be known. An effective assay must evaluate the actual biological toxicity of the shellfish being tested. For the chemical assay this requires the summated toxicity of all the... 

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