Environmental Risks of Nanomaterials - Nanotechnologies for Water Environment Applications - page 604

When performing exposure assessments on NMs for which there are no experimental
data, complex structured models and computer simulation can provide vital tools to
provide a predictive capability and estimated data for risk management and making
correct decisions (Allen and McVeigh, 2004). Generally, such model designs and
developments require information on particle surface properties, size and
biodegradability so that simulation can provide an effective tool for hazard identification
and risk management of NMs (Gatti and Rivasi, 2002). The choice of models depends
on the NMs at hand and may be, to some extent, dependent on which model the decision
maker is most familiar with. Before the environmental fate, transport and multimedia
partitioning of NMs can be modeled, reliable experimental data must be acquired for a
variety of NMs.
Multi-Criteria Decision Analysis (MCDA), or Multi Criteria Decision Making
(MCDM), is a useful tool to support decision makers in risk management. MCDA or
MCDM is a discipline aimed at supporting decision makers making numerous and
conflicting evaluations. MCDA or MCDM allows the decision maker to link
performance information with decision criteria and weightings from experts, and thus
allows visualization and quantification of the trade-offs for the decision-makers. It is
therefore becoming a powerful and scientifically sound decision-making tool for NM
risk assessment and management (Linkov et al., 2007). This approach will aid our
understanding of the nano-bio interactions, which in turn will facilitate the development
of improved simulation tools to predict the environmental risk and impact of NMs.
Models focusing on the fate and distribution of particulate matter (air models) and/or
colloidal materials (soil, water, landfill leachates, ground water) will also be useful for
risk assessment of NMs.
17.4.2 Health Risk Evaluations
According to the USEPA (2008), the terms 'hazard' can be defined as the
inherent toxicity of a compound; the term 'risk' can be defined as a measure of the
probability that damage to life, health, property, and/or the environment will occur as a
result of a given hazard. In general, if the probability of an event occurring is high and
the consequences are significant, the risk is considered to be high. However, human
health risks are considered to be higher, if the hazard or consequence is adverse health
effects, even though the probability of occurrence is low.
For the assessment of health risks of NMs, evaluation of both a potential for
exposure and a hazard that results after exposure is necessary. Exposure depends on
many factors such as the manner for handing NMs, the magnitude of the sources, the
partition of NMs to various phases (or compartments) and their mobility in these phases
(or compartments), and their persistence in the environment. Subsequently, risk
evaluations for NMs can be performed.