Lethality bioassay

Requiring low-sample volume micro-scale tests for its cost-effective application, the PEEP index has thus far employed bioassays with bacteria, algae and microinvertebrates. While well-standardized toxicity tests using freshwater fish existed at the time of the PEEP s conception in the early 1990 s (e.g., the Environment Canada fingerling rainbow trout 96-h lethality test to assess industrial wastewaters), they were excluded because of their large sample volume needs (e.g., close to 400 L of effluent sample required to undertake a multiple dilution 96-h LC50 bioassay in the case of the trout test). In addition to effluent sample volume, the cost of carrying out salmonid fish acute lethality bioassays for the 50 priority industrial effluents identified under SLAP I (the first 1988-93 Saint-Lawrence River Action Plan) was prohibitive. 

Padmaja, R., P.C. Arun, D. Prashanth, et al. 2002. Brine shrimp lethality bioassay of selected Indian medicinal plants. Fitoterapia 73 508-510. 

Janackovic, R, V. Tesevic, P.D. Marin, et al. 2008. Brine shrimp lethality bioassay of selected Centaurea L. species (Asteraceae). Arch. Biol. Sci. 60(4) 681-685. 

The impact that a silver compound has in water is a function of the free or weaMy complexed silver ion concentration generated by that compound, not the total silver concentration (3—5,27,40—42). In a standardized, acute aquatic bioassay, fathead minnows were exposed to various concentrations of silver compounds for a 96-h period and the concentration of total silver lethal to half of the exposed population (96-h LC q) deterrnined. For silver nitrate, the value obtained was 16 )-lg/L. For silver sulfide and silver thiosulfate complexes, the values were >240 and >280 mg/L, respectively, the highest concentrations tested (27). 

A bioassay is a test designed to measure the effect of a chemical on a test population of organisms. The effect may be a physiological or biochemical parameter, such as growth rate, respiration, or enzyme activity. In the case of drilling fluids, bioassays lethality is the measured effect. 

A word of caution should be made with respect to estimating tenability for human exposures. Experimental LC values are determined using rat lethality as the bioassay. Judgement should be exercised for human tenability, with limits set considerably lower than FED summation at unity. An FED limit of, perhaps, 0.3 may be more appropriate for assessment of the potential escape of humans. 

Mitchell, D.G., J.D. Morgan, J.C. Cronin, D.A. Cobb, G.A. Vigers, and P.M. Chapman. 1986. Acute Lethal Marine Bioassay Studies for the U.S. Borax Quartz Hill Project. Canad. Tech. Rep. Fish. Aquat. Sci. No. 1480 48-49. 

The toxic effects of pesticides can be diverse and depend on the sensitivity of organisms to these toxicants, and the pesticide concentration or bioavailability. Typically, the short- and long-term effects of pesticides have been evaluated through acute or chronic toxicity bioassays, respectively, using lethality endpoints and sublethal endpoints (e.g., growth and reproduction), particularly these last in chronic bioassays. 

Some sophisticated guessing goes into dose selection. Knowledge of the minimum acutely toxic dose helps the toxicologist pick the highest dose to be used it will be somewhere below the minimum lethal dose. There is usually little basis for deciding the lowest dose it is often set at some small fraction of the high dose. Whether it turns out to be a NOAEL will not be known until the experiment is completed. Sometimes bioassays have to be repeated to identify the NOAEL. 

The more classical approach to assess the presence of marine biotoxins in seafood is the in vivo mouse bioassay. It is based on the administration of suspicious extracted shellfish samples to mice, the evaluation of the lethal dose and the toxicity calculation according to reference dose response curves, established with reference material. It provides an indication about the overall toxicity of the sample, as it is not able to differentiate among individual toxins. This is a laborious and time-consuming procedure the accuracy is poor, it is nonspecific and generally not acceptably robust. Moreover, the mouse bioassay suffers from ethical implications and it is in conflict with the EU Directive 86/609 on the Protection of Laboratory Animals. Despite the drawbacks, this bioassay is still the method of reference for almost all types of marine toxins, and is the official method for PSP toxins. 

The freshwater cnidarian Hydra attenuata was only recently exploited to assess the acute lethal toxicity of wastewaters [37,104]. The advantages of using Hydra for bioassay include its wide... 

The lethal activity of the isobutylamides on C. pipiens is shown in Table II. The amides were dissolved in 0.1% acetone in distilled water to give concentrations of 1-20 ppm. Third-instar C. pipiens were transferred (5 larvae/10 ml test solution) into 1 oz. plastic cups using a 1 x 1-inch circle of ordinary window screen. Each treatment was replicated 4 times and the minimum concentration of each compound which caused 100% mortality (LDioo) within 48 h at 25 C and 16L/8D photoperiod was determined. In a result similar to that found with the artificial diet bioassay with lepidopterous larvae, pellitorine proved to be the most toxic of the assayed amides (LDjqq = 5 ppm). 

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