Environmental Engineering Reference
In-Depth Information
Despite its importance, there has been little systematic consideration of problem
formulation for manufactured nanomaterials, either generically within risk assess-
ment methodologies or, more specifi cally, for one substance or a mixture of sub-
stances (Owen and Handy, 2007).
Risk assessments may be requested by regulators as the basis for coordinating
dispersed or incomplete evidence on risks. In these situations, whilst a risk assess-
ment framework may provide a valuable ' route map ' for decision makers, risk
assessors still have to assemble and structure the evidence to support the safe use
of a chemical. This includes identifying individual lines and strength of evidence
and presenting the overall weight so as to inform the characterisation of risks and
its management to acceptable levels of residual risk. The triggers for initiating a
risk assessment are likely to include:
• situations where signifi cant consequences are suspected following exposure;
• where evidence on the adverse consequences of exposure is emerging;
• the presence of contradictory or incomplete evidence on hazards;
• situations where the mechanisms and priorities for risk management are unclear;
or
• where there are opportunities to act in a precautionary fashion to prevent future
exposures.
Even for complex hazards that give rise to a wide range of endpoints
within occupational, consumer, public health and environmental settings, an
analysis of the sensitivities of the risk estimates to specifi c aspects of exposure
(e.g., release rates, distance to exposure points, exposure factors, critical receptor
groups) can provide the basis for preventative interventions that dramatically
reduce risk.
As a prerequisite to a discussion of nanomaterials, it is useful to set out some of
the key themes for regulatory risk assessment, illustrated here by reference to
industrial chemicals and occupational exposure. This sets the scene for a discussion
below on scoping out needs for risk assessment for nanomaterials.
The majority of regulatory risk assessment guidelines have ' triggers ' that deter-
mine whether a risk assessment is required by a manufacturer or operator and the
quantity and type of information required within it. One important initial trigger
for risk assessment is the mass of chemical manufactured or imported per year (i.e.
12 calendar months), as shown in Table 10.1.
The initial risk assessment trigger in the majority of countries shown in Table
10.1 is 1 tonne/year (except New Zealand where the act of importing or manufac-
turing the chemical is the trigger). The amount of information required at that point
differs. Indeed, within the European Union, substances manufactured or imported
at levels exceeding 1 tonne/year must undergo registration with further information
required at sequential triggers. The chemical categories excluded from the risk
assessment frameworks for industrial chemicals include polymers, radioactive
materials, medicinal products and food stuffs, which are considered under other
legislation. Non-isolated intermediates, by-products and chemicals produced inci-
dentally during production are not considered as separate compounds but will be
included in the assessment of the initial compound. Naturally occurring biological
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