Environmental Engineering Reference
In-Depth Information
exposure to nanomaterials in the work place whilst using approved safety proce-
dures. However, the long term risk and the effectiveness of these measures will only
be shown by long term monitoring of the workplace.
Waste disposal of nanomaterials is also an area with many knowledge gaps.
Knowledge on the suitability of incineration as a disposal method for carbon-based
and other non-metallic nanomaterials is lacking. It is unclear whether nanomaterials
would be completely destroyed during incineration or whether they will contribute
to air pollution. Some aspects are well known, such as the combustion chemistry
of soot particles (Elmquist et al. , 2004), but it is unclear as to how much of this
existing knowledge could be directly transferred to C 60 or other carbon-based
nanomaterials. Household products containing nanomaterials are likely to be dis-
posed of at landfi ll. The chemical fate and behaviour of nanomaterials in landfi ll
is unknown and there are concerns that nanoscale materials may penetrate the clay
lining materials of the landfi ll, releasing nanomaterial leachate into the water table.
Managing uncertainty in the risk assessment of manufactured nanomaterials is
likely to be critical because the relationship between environmentally relevant
doses and the potential toxicological responses in human and environmental recep-
tors is not well characterised (Nel et al. , 2006; Renn and Roco, 2006; Balbus et al. ,
2007a). Practitioners can expect to have to assemble and weigh the evidence (dis-
cussed further in Mayo and Hollander, 1991; Forbes and Calow, 2002; Hrudey and
Leiss, 2003 ; Weed, 2005 ; Balbus et al. , 2007b) from various research studies and
apply precaution (discussed in ILGRA, 2001; Harrison and Holmes, 2006), espe-
cially where irresolvable uncertainties in the assessment suggest that signifi cant
consequences might occur.
10.7
Summary
The current consensus is that existing risk assessment frameworks and their com-
ponents are, in principle, appropriate for the risk assessment of nanoparticles and
nanomaterials, but that implementation may be associated with signifi cant new
issues. These issues relate in part to two features of nanomaterials, their diversity
and the complexity of their behaviour in natural systems and the uncertainty this
may introduce to risk assessments, notably in the quantifi cation of hazard and
quantitative predictions of exposure. Many aspects of diversity and complexity are
covered in other chapters of this topic.
Reducing uncertainty in hazard and exposure assessment will require signifi cant
and potentially lengthy research into behaviour, interaction and bioavailability in
natural systems for any one nanomaterial, let alone any variants of those materials
associated with the addition of active chemical groups onto the surface of the mate-
rial. This must be considered alongside the ever growing diversity of nanomaterials
and their functionalities associated with rapid technological development.
Commitment to reduce uncertainty in hazard, exposure and risk assessment must
be justifi ed by robust problem formulation, underpinning what risk assessors call
'justifying the intent' to undertake a risk assessment. To date, while considerations
of the technical aspects of exposure and hazard continue, far less consideration has
been given to this critical phase of risk assessment.
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