Organ lethality, species differences

Toxicity tests are very useful tools to identify the possible impacts of the PAHs on aquatic organisms. Lethality tests are considered good indicators of the toxicity of different chemicals and for different species, while the sub-lethality tests are interesting since they consider the impacts on the population by evaluating the effects on the organisms reproduction and growth (Wake, 2005). 

When tests are performed on terrestrial animals, it is common to apply single (measured) doses orally, topically (i.e., applied to the skin or cuticle), or by injection into tissues or body fluids. There can be very large differences among groups of organisms and among species in their susceptibility to the toxic action of chemicals. The selective toxicity ratio (SER) is expressed in terms of the median lethal dose, and is important for the differentiation between beneficial organisms and pests ... 

Except for H. azteca, lethality was observed at remarkably similar ETNT concentrations for a variety of experimental species and sediment organic carbon content. However, accurate comparisons of the toxicity of TNT-spiked sediments using different sediments and species should take into account the variable relative concentration of parent and transformation products in the different exposure sediments because of potential toxicity differences among compounds and nonadditive mixture interactions. 

Acute toxicity and short-term bioaccumulation. Studies of acute toxicity measure the lethal response after 24 or 96 h of exposure in various bodies of water. Test species should be chosen from amongst most commonly used organisms and standardized procedures should be applied. The test should include at least three different trophic levels, namely primary producers, primary consumers and secondary consumers. Normally, organisms such as green algae, daphnids and fish are utilized. 

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