Standard methods in nano-ecotoxicology has been applied to screen particles for biological effects, but the appropriateness of these test methods, with respect to nanoparticles and especially with respect to exposure conditions, still remains to be systematically evaluated. The goal in TP2 is to identify limitations to existing ecotoxicological test methods and develop alternative test methods and/or exposure procedures for nanoparticles.
The test organisms will be unicellular green algae, filter-feeding crustaceans, and sediment worms in short- and long-term (chronic) tests. Specific areas of focus include the influence of particle aggregation behaviour on exposure concentrations as evaluated by toxicity test results, particle interference on measuring methods, mode of exposure, expression of dose, influence of media and mode of effect.
Links between toxicity of nanoparticles and material properties will be studied by comparing available physical and chemical characteristics of nanoparticles with results of toxicity tests in different exposure scenarios (media composition, pH, presence of natural organic matter). In all experiments the kinetics of the processes will be at the centre of attention. As mentioned above the initial focus will be on gold nanoparticles since they offer a unique opportunity of studying the influence of particle size, shape, and coatings/stabilizers on the toxicity. Thus, a statistical test design covering three different sizes (10, 30, and 50 nm), two different sizes (spherical, rods), and three different coatings/stabilizers (starch, mercapto-dodecylcarboxylate, citrate) will be studied in short-term algal, daphnia, and worm tests. The most interesting combinations will subsequently be studied in long-term reproduction tests with daphnia and studies with TiO2 and Ag will be designed based on the experiences gained with AuNPs.
All of these activities are interacting with TP1 and TP3 through common methodologies for analysis and exposure conditions. While direct exposure of organisms via the water may not be the major exposure route, and since the toxicity of a substance is closely related to its bioavailability, results of uptake and bioaccumulation studies generated in TP3 will be taken into account for evaluation of the test systems and the potential effects of nanoparticles. As described above, data from TP2 will assist the test design in TP3 and as shown in Figure 1 direct input will be delivered to TP4.