Risk Assessment of Manufactured Nanomaterials - Environmental and Human Health Impacts of Nanotechnology - page 387

Regulatory approaches to risk assessment have been developed internationally
for assessing existing and new high volume production chemicals (NRC, 1983; IPCS,
1999; REACH technical guidance documents, accessed at http://echa.europa.eu/
reach_en.asp; EC JRC, 2003).
Notwithstanding the value of these approaches and their systematic processes,
much of the fundamental science on which risk assessments are based have a
degree of uncertainty attached. Given this, it is essential to recall the purpose of
the assessment - to judge the signifi cance of the risk and inform decisions on how
best risks should be preventatively managed. It is essential to ensure that risk esti-
mates do not infer a level of precision that the underpinning evidence base cannot
support. In practice, risk assessments incorporate both qualitative and quantitative
elements (Harrison and Holmes, 2006) and are applied using tiered approaches
that allow for early screening and prioritisation with the defensible and judicious
use of quantitative techniques for key features of the problem under study (DETR
et al. , 2000 ; Figure 10.1 ).
Risk assessors have learnt, given the complexity and data needs involved, that
maintaining a focus on the essential questions of 'what/who is at risk?' , and ' what
is it/are they at risk from?' is critical for sound decisions on managing risk. Good
problem formulation, conducted in a consultative and participative fashion with
inputs from a range of stakeholders, guides the assessment towards the key expo-
sure routes and biological effects of concern (Pollard, 2006; Owen and Handy, 2007).

Problem formulation

Stages within each tier

Tiered Risk Assessment

Risk
prioritisation

Hazard identification

Hazard assessment

Tier 1 Qualitative

Risk estimation

Tier 2 Generic quantitative

Risk evaluation

Tier 3 Detailed quantitative

Options Appraisal

Economics Technology

Social issues Management

Risk management

Continuing data collection, monitoring and process iteration

Figure 10.1 Design of risk assessment and risk management framework showing qualitative
and quantitative risk assessment and the stages required for each tier (after DETR, et al.,
2000).