Exposure to Nanoparticles - Environmental and Human Health Impacts of Nanotechnology - page 304

materials is often dependent on their specifi c surface area rather than their com-
position (Tran et al. , 2000). Epidemiological evidence from industrial processes,
such as the manufacture of carbon black, where workers may potentially be exposed
to nanoparticles, also indicates potential respiratory health issues (Gardiner et al. ,
1992 ). The large specifi c surface area, crystalline structure, reactivity and exotic
properties of some nanoparticles, coupled with what appears to be an imminent
shift away from laboratory based development to industrial manufacture, strongly
indicates a need for a clearer understanding of the risks associated with these
materials.
Since the publication of the UK Royal Society/Royal Academy of Engineering
report in 2004 (RS/RAEng, 2004), there has been a signifi cant increase in research
activity relating to the potential risks to health and the environment from nano-
materials. Much of this work has been concerned with the hazardous nature of these
materials and this is discussed in detail in other chapters in this topic. Up to this
point, very little of this activity has addressed the question of exposure. What is
meant by exposure in this context? Exposure is generally considered in terms of
contact between a potential stressor, in this case nanoparticles, and an individual
population or environment. Exposure is usually measured in terms of its intensity
and duration (or frequency). As is well known, an understanding of exposure is
critical in risk assessment and management, along with an understanding of hazard,
which is considered elsewhere in this topic. Knowledge of plausible exposure levels
and duration enables realistic interpretation of those response relationships. Control
of exposure (to zero) effectively removes the risks from nanomaterials. Without
exposure there is no risk.
Given the importance of exposure in understanding and controlling risk, it is
both surprising and disappointing that until now such little attention has been given
to understanding, quantifi cation and assessment of exposure to nanoparticles.
Reviewed in this chapter is the potential for exposure to aerosols from processes
involving the deliberate development and manufacture of nanoparticle products.
In particular the following have been considered:

• terminology and characteristics of nanoparticles;
• potential routes for human exposure;
• industrial sources of occupational exposure;
• levels of exposure;
• means of, and effectiveness of, control measures;
• potential numbers of people exposed.

8.2 Physical Characteristics and Properties of Nanoparticles

8.2.1 Terminology and Defi nitions

In occupational health the importance of particle size has been well understood for
some time. In relation to the transport of aerosols in a workplace, the probability
that the aerosol will be inhaled, the region of the respiratory tract that they will
reach and whether or not they will deposit, all depend on particle size. This has led