Environmental Engineering Reference
In-Depth Information
also been shown to generate ROS (Stone et al. , 1998), it was hypothesised that the
two might interact. Mixing 14 nm carbon black with FeCl 3 , FeSO 4 or CuSO 4 in a
cell free environment, resulted in potentiation of ROS production, as assessed by
the DCFH assay. Wilson et al. (2002) also investigated the interaction in vivo by
instilling a mixture of the 14 nm carbon black and FeCl 3 solution into the rat lung.
The iron salt was found to potentiate the carbon black induced lung infl ammation,
showing that the particles and metal salts clearly interact, both in vitro and in vivo .
At the time of this publication, the discussion of these results was limited to the
relevance to air pollution research, but with many nanoparticles, including soluble
metal ions, such fi ndings are also useful to inform the potential mechanism of toxic-
ity of manufactured nanoparticles.
Wilson et al. (2007) also investigated the interaction between zinc chloride and
carbon black. In this study, the authors found that zinc could not potentiate ROS
production by the carbon black particles, but that it did induce a large synergistic
activation of macrophages in vitro , as indicated by production of the pro-
infl ammatory cytokine TNF
. Again, this data is highly relevant to manufactured
nanoparticles, some of which (e.g. quantum dots) are coated in zinc sulphide.
There have also been suggestions that diesel exhaust air pollution particles
(DEP), which contain substantial amounts of combustion derived nanoparticles can
interact with airborne allergens, inducing an adjuvant effect. This means that when
inhaled in the presence of pollen, or dust mite allergens, the resultant allergic
response is enhanced (Takano et al. , 1998). The adjuvant effects of nanoparticles
are actually being exploited in nanomedicine in the development of vaccines (Peek
et al. , 2008 ).
α
9.3
Engineered Nanoparticles
As mentioned previously there is a vast array of engineered nanoparticles,
many of which are described in previous chapters, which need to be considered in
terms of their toxicology. While inhalation is still important as a route of exposure,
especially in an occupational environment where powders are employed, other
routes of exposure, such as ingestion, dermal adsorption and injection/implantation,
also need to be considered. Therefore, if every new nanoparticle was to be tested
for toxicity using a protocol relevant to multiple doses, and multiple routes of
exposure, thousands of tests would be required. Add to this, variations in formula-
tions, interactions with other toxins and variability in susceptibility between indi-
viduals, and the number of experiments required is almost beyond comprehension,
and certainly beyond budget. Instead of testing every nanoparticle for every rele-
vant scenario, in the near future it will be necessary to try to generate some general
rules regarding the physicochemical factors which drive the mechanism by which
particles interact with biological systems, and therefore their toxicity. For this
reason, the following section is broken down by nanoparticle type. While it is still
unclear which factors are most important in determining toxicity, classifi cation of
nanoparticle by material is a fi rst useful step in the absence of more useful
information.
Search WWH ::




Custom Search