Exposure to Nanoparticles - Environmental and Human Health Impacts of Nanotechnology - page 325

In conclusion, scientifi c evidence, so far, has demonstrated that particle specifi c
surface area and surface reactivity is likely to be the metric of choice to describe
the infl ammatory reaction to deposited particles in the proximal alveolar region of
the lung. For nanoparticles, their potential dispersal to other organs as well as the
possibility of exposure by other routes such as dermal or ingestion mean that pos-
sible health risks beyond the lung can not be ruled out. Further research to generate
vital data on the possible mode action of nanoparticles in the extra-pulmonary
system is needed in order to assess realistically the health risks to nanoparticle
exposure.

8.3.3 Methods of Measuring and Characterising Exposure to Nanoparticles

8.3.3.1 Rationale for Measurement

Good information about levels of exposure in the workplace or other scenarios
requires measurements to be made. The types of measurements which are appropri-
ate depend on the purpose of the measurement programme. In PD 6699-2:2007,
' Guide to safe handling and disposal of manufactured nanomaterials ' (BSI, 2007b ),
the following are identifi ed as typical activities which a sampling programme may
support:

• identifi cation of sources of nanoparticle emissions;
• assessment of the effectiveness of any control measure implemented;
• ensuring compliance with any workplace exposure limit or self-imposed (in-
house) exposure standard;
• identifying any failures or deterioration of the control measures which could
result in a serious health effect.

In practice, each of these tasks will require specifi c and often different types of
instrumentation, and an appropriate study design and strategy. A range of instru-
mentation is available; this is discussed in Section 8.3.3.2. Possible strategies are
discussed in Section 8.3.3.3 .

8.3.3.2 Measurement Methods

Current best practice to measure the exposure of an individual to a chemical or
other material present as an aerosol is to use a personal sampling device to collect
a sample biologically relevant fraction of the aerosol (HSE, 2000). In occupational
hygiene, it is common practice to use samplers conforming to the inhalable or
respirable convention. Samples collected in this way, usually over a full working
shift, are then subsequently assessed either gravimetrically or via chemical analysis
to determine the mass and, hence, average concentration over the defi ned period.
These samplers provide an estimate of mass concentration, from which personal
exposure may be derived.
A range of sampling instruments is available to collect samples for analysis.
Usually these are small devices, comprising a selection stage, a fi lter (the combina-
tion often referred to as the sampling head) and a sampling pump mounted on the