Risk Assessment of Manufactured Nanomaterials - Environmental and Human Health Impacts of Nanotechnology - page 399

Human or
environmental
exposure likely?

N

Reassess if use,
manufacture or
disposal changes

Nanomaterial

Y

Y

Particles less than
100nm

Toxicity
of substance
known?

Full risk
assessment
required

N

N

Y

Y

Existing data may
be sufficient

Do
particles need
to be assessed
separately

N

Homogeneous
particles?

Y

Do particles
rapidly agglomerate
or coalesce?

Existing exposure
data may be
sufficient

Y

N

Are
other chemicals
absorbed into the
particle?

Y

High priority for
study

N

Existing exposure
data may be
sufficient

Significantly
increased
reactivity?

Y

Figure 10.4 Decision fl ow chart for the risk assessment of nanomaterials and

nanoparticles.

occupational, consumer, public health and environmental settings (Linkov et al. ,
2007 ).
Criteria already exist for evaluating the plausibility of associations in disease
causation. For instance, Bradford Hill's criteria (Hill, 1965) attempted to separate
causal from non-causal explanations of observed associations by reference to a
number of criteria (defi ned by Hofl er, 2005 ) including:

• strength of association (a strong association is likely to have a causal
component)
• consistency (reproducibility)