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Posted: August 5, 2010
Safe Work Australia publishes reports on methods to reduce the risk of exposure to nanomaterials
(Nanowerk News) Safe Work Australia commissioned RMIT to undertake a survey of the current substitution/modification practices used in Australian nanotechnology-related activities and a literature review in order to determine the potential substitution/modification options that may reduce the toxicity of engineered nanomaterials used in Australia.
a) There were 38 respondents to the survey, who reported working on a range of different
types of nanomaterials. The respondents' organisations were primarily universities,
commercial/industry and government research groups. The most common nanomaterials
handled are metal oxides, metals and carbon nanotubes and the most common areas of
application are into energy, medical, surface coating and textile uses.
b) Many organisations (27/35), and notably universities (20/21), manufacture their own
engineered nanomaterials, and a significant number also purchase them from overseas or
from within Australia.
c) A number of respondents obtained work health and safety information about the
nanomaterials that they are using from an MSDS. The main work health and safety issues
examined for engineered nanomaterials are handling and storage, physical and chemical
properties, toxicological data and exposure controls/personal protective equipment (PPE). The available information on these topics is limited.
d) Most respondents indicated that substitution/modification is used to change the functional
properties of the product. A work sector analysis indicates that
substitution/modification occurs more in university research and less in commercial/industry
research which is as expected in product development.
e) The five properties that are manipulated by modifying or substituting engineered
nanomaterials by the highest number of organisations are particle size, physical properties,
agglomeration properties, chemical properties and conductive properties. A small number of
respondents indicated that they use substitution/modification to change the health or
f) Adding functional groups (17 responses) and modifying surface characteristics (16
responses) are the two most popular methods for the substitution/modification of engineered
nanomaterials. Others include changing the form of the material, the particle size and
shape, and the crystalline structure.
g) Australia's nanotechnology activities are generally at the early stage of nanomaterial
development, i.e. more focussed on de novo research than later stages of product
development/production. However substitution/modification methodologies are well known
and used in Australia and thus there is an existing capability that might be applied more
broadly to work health and safety related purposes.
Summary of the literature review
a) The mechanisms by which nanoparticles enter biological systems and subsequently
cause toxicity are dependent on factors such as nanoparticle or aggregate size,
physicochemical characteristics of particle surfaces (e.g. surface charge), biocompatibility
and cell-specific effects on nanoparticle uptake. Various substitution and modification
strategies for a range of nanomaterials have been described in the scientific literature.
b) Carbon nanotubes (CNTs) can be functionalised and surface-modified to increase their
solubility and biocompatibility. It is also possible to reduce their chronic toxicity potential by
using short CNTs and keeping their length to less than 5µm. Further investigation of the
toxicity of these modified CNTs needs to be made to assess the extent of the reduction in
potential workplace hazard.
c) When formulating a new product or use, the toxicity of fullerenes can be controlled by
attaching functional groups to the fullerene moiety. Specifically, attaching water solubilising
groups such as carboxyl or alcohol groups, will increase the solubility and lead to reduced
toxicity of the prepared fullerene. This modification will also alter particle aggregation
behaviour in water and its potential bioavailability and reactivity in aquatic systems, and this
area requires further investigation.
d) It can be concluded that when formulating a new nano titanium dioxide (TiO2) product or
use, its potential toxicity can be controlled by varying the crystalline form used, i.e. use the
less reactive rutile form rather than the more reactive and photocatalyitc anatase form where
e) It can be ascertained that nano ceria under specific conditions exhibits antioxidant and
biocompatible properties. However, outside this range of conditions antioxidant behaviour is
not exhibited, and its redox cycling ability may be pro-oxidant. In an aquatic system, nano
ceria has been found to be more toxic than the micron sized particles. It is not possible at
this stage to suggest modifications that can be made to nano ceria until more data are
f) It can be concluded that nano zinc oxide (ZnO) used in sunscreen type products and for
other similar applications exhibits a low level of toxicity and dermal penetration into the
human body. There are surface modification options available for ZnO which have the
potential to reduce toxicity further, in addition to structural modifications that help retain
functionality, such as doping the ZnO crystalline lattice.
g) Nano gold particles can be surface-coated, e.g. with phosphatidylcholine, or
encapsulated with biocompatible biopolymers, e.g. chitosan or polyethylene glycol, to
reduce toxicity, whilst retaining functionality and useability. Alkanethiol-capping may be used
to increase biocompatibility and also functionalise the nano gold for a range of biomedical
h) Nano silver can be surface modified with hydrophilic groups, such as phosphorylcholine
or phosphorylethanolamine, to increase biocompatibility. Such modifications would also
decrease its antibacterial activity and potential usefulness in many current applications.
However, further functionalisation of biocompatible forms of nano silver may provide
potential new applications, such as in biomedical diagnostics and biosensors.
i) It is possible to modify the surface of nano silica with alkylsilylation, polymers or proteins to
increase its hydrophobic character, causing increased particle aggregation and reduced
direct membrane effects, and thereby improving its biocompatibility. Due to potential toxicity
of silica nanomaterials with high aspect ratios, consideration should also be made as to
whether nanowires may be substituted with nanospheres, while retaining functionality for a
j) It is possible to encapsulate quantum dot cores with stable shell coatings made from
biocompatible polymers, e.g. chitosan or polyethylene glycol, to significantly reduce their
cellular uptake and degradation, and consequently their cytotoxicity, whilst retaining
functionality and useability.
Implications for work health and safety
There are known methods that can be used to substitute/modify engineered nanomaterials
that are used, or researched, in Australia. The methods of surface modification,
encapsulation, particle size control, functional group addition and crystalline phase type
control can each be employed for different engineered nanomaterials to decrease their
potential toxicity. However in some cases, such modifications may affect the functionality of
nanomaterials in relation to intended end-uses.
If the researchers, developers and manufacturers of engineered nanomaterials adopt these
methods then it is possible to re-engineer nanomaterials in the early stages of development
to reduce the potential toxicity of manufactured nanomaterials. The downstream effect of
this will be to reduce the risk posed by the use of these nanomaterials not only in the
workplace but also in the general community.
Source: Safe Work Australia
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