Challenges of Regulation and Risk Assessment of Nanomaterials

Comparing the reproductive toxicity of ZnO nanoparticles, bulk ZnO, and
ZnCl2 to the earthworm Eisenia Andrei
Svendsen C. 1 , Spurgeon D. 1
1 Centre for Ecology and Hydrology, Maclean Building, Benson Lane, Crowmarsh Gifford, Wallingford,
Oxfordshire OX10 8BB, UK
The field of nanotechnology is evolving rapidly and the development is largely driven by the great
possibilities for industries to improve the properties of their consumer products using nanoparticles
(NPs). Fate modelling studies conducted for TiO2, that have considered NPs release from sunscreens,
has highlighted that the majority of NP releases to wastewater are likely to end up closely associated
with the activated sludge during sewage treatment. Since much of this sludge is directly deposited to
land in many countries, it is likely that a large volume of post production NPs will end up in soil.
With NP increasingly likely to be reaching the soil compartment, there is a potential for toxic effects
on the soil and soil surface fauna and primary producers. To date studies of metal oxide nanoparticles
in soil systems have focussed almost exclusively of first generation materials produced for use in
consumer production. From the studies conducted with metal and metal oxide NPs, it has so far
largely been seen that observed effects are likely to be associated with metal ion release during
dissolution. Indeed our own studies conducted using a range of ZnO NP have confirmed that the
prevalence of free ion, rather than NP associated, toxicity as the principal determinant of toxic effect.
While initial evidence points to the importance of ionic effects, studies with soil organisms have to
date been conducted only using standard artificial media rather than natural soils. This means there
is uncertainty about how effect observed in standard tests relate to toxicity expected in natural soils
in which key soil properties (pH, cation status, organic carbon content) can vary greatly. Studies to
investigate such effect are a focus for current research.
While toxicity may be driven by free metal toxicity, studies conducted with soils species have shown
the direct uptake of gold, copper and ZnO NPs. To understand the potential toxicity associated with
metal effects, using both classic model species such as the soil dwelling nematode Caenorhabditis
elegans and other ecological relevant taxa, analysis of expression change for pathways with a
potential role in toxicosis (e.g. metal binding proteins, ROS defence) as well as identification of new
pathways associated with toxicity are already proving informative.
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