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Approaches

Acute or Chronic? Direct or indirect effects?

Nanomaterials have the capacity to affect the biological and physical compartments (ground, surface and ground water, atmosphere, sediment) of the environment. Most of the studies have been performed in the aquatic environment, mainly in fresh water. Because of  the difficulty of characterizing nanomaterials in the ground or in the sediments, little data are available.

Several studies concern the acute toxicity (response to an occasional and massive aggression) rather than the chronic toxicity (response to a regular but minor aggression).

A direct effect is observed by cellular assimilation of nanoparticles: intrinsic toxicity. In the sludge's from  water treatment plant, the soils or the surface waters, nanoparticles are in interaction with others polluting's (oxides, silicates, phosphates). Due to this adsorption, indirect effects may be observed.

Is laboratory experimentation realistic?

441_toxicites

Methodology principles.

The properties of nanoparticles which can evolve according to experimental conditions, and the effects observed in laboratory on certain organisms could be different from real effects in a natural environment.

For a large majority, the ecotoxicity studies have been realized with a model specie (algae, bacteria,…) exposed to a nanomaterial in a single medium (water, ground or sediments) on short periods (not exceeding 3 weeks). It is thus possible to assess  the toxicity and the toxic mechanisms of the effects of nanomaterials concerning a specie. But, this kind of studies doesn’t allow to evaluate the impacts of single or mixing nanomaterials and of their residue at the ecosystem level as a whole.