Analysis and Characterization of Manufactured Nanoparticles in Aquatic Environments - Environmental and Human Health Impacts of Nanotechnology - page 250

experiments. In a recent review (Foss Hansen et al. , 2007) it was shown that although
size determinations are becoming more common (17-96% of exposure and effects
studies) other relevant properties are rarely characterized (e.g. surface area in
6-33% of studies).
Assuming that all relevant physico-chemical characteristics are available from
tier 1 studies (material characterization), and that colloidal stability/agglomeration
rates, deposition rates and dissolution rates are determined in the fate studies (tier
2) in the same test media as in effects studies, then the following additional confi r-
mation analysis are recommended as a minimum set:

• Determination of total concentration, fi lterable (0.22 µ m fi lter nominal pore size)

100 nm) concentration of the major
composition of the NPs after an appropriate digestion method, during the course
of experiments.
• Tracking of changes in size distribution or size average in the aquatic experi-
ments, in order to trace agglomeration kinetics.
• C o n fi rmation of enhanced depositition onto organisms or test system induced
by mucus or excudates.

and centrifugable (equivalent diameter ∼

The recommendation of methods for the above analyses based on minimum
perturbation, general availability, ease of use, cost, analysis time are:

• Chemical composition by standard methods (e.g. AAS, ICPMS) after appropriate
digestions/separations.
• Dynamic light scattering (bearing in mind its limitations).
• Nanoparticle tracking analysis is very promising but needs validation and is
rarely available yet.
• Turbidity is a simple, inexpensive but crude method to follow agglomeration.
• Samples for electron microscopy can be prepared in any laboratory for subse-
quent analysis in specialized lab.

6.3.4 Monitoring Nanopollution

The emissions of manufactured NPs will most likely follow the trends of the devel-
opment of nanotechnology (Roco, 2005), and the increasing incorporation of
nanomaterials in consumer products (http://www.nanotechproject.org/inventories/
consumer/), medicine and industrial catalysts, and so on. There are very few studies
on the prediction of environmental concentrations of manufactured NPs, but one
attempt predicted

g l − 1 of titanium dioxide, when assuming most current products
would be shifted to nano-sized titanium dioxide(Boxall et al. , 2007 ). Another study
based on usage patterns in Switzerland used a life-cycle perspective (substance fl ow
analysis) to derive predicted environmental concentrations for nano-sized titanium
dioxide as 0.7- 16

µ

g l − 1 (Mueller and Nowack, 2008). There are still many unknown
parameters in these models that could be improved by systematic studies on leach-
ing patterns in various product life stages, and results from a few such studies are
becoming available. One paper simulating regular wash procedures of nano-sized
silver coated socks studied leaching of nano-sized silver and silver ions using total
digestions, electron microscopy, and a silver ion selective electrode (Benn and

µ