Field and Laboratory Measurements Related to Occupational and Consumer Exposures - Safety of Nanomaterials along Their Lifecycle - page 277

Exposure modeling has been paid much attention in the last few years. The con-
ceptual model for inhalation exposure to nanoparticles was proposed by Schneider
et al. (2011), built on previously proposed models, for example, by Maynard and
Zimmer (2003), who already addressed specific issues related to size distribution
evolution through coagulation, settling, and diffusion. Several other research groups
have addressed the specific aerosol dynamics for nano aerosols especially with
regard to the evaluation of size distribution over time by coagulation in indoor air,
for example, Seipenbusch et al. (2008), Rim et al. (2011), Anand et al. (2012), and
Asbach et al. (2014). Walser et al. (2012) used a one-box model to predict temporal
fluctuations of particle number concentration due to accidental events.
A number of pragmatic tools for risk management or risk prioritization, for exam-
ple, control banding tools, have been developed (Brouwer 2012a) and a few use the
conceptual model as the basis for the exposure assessment band of the tool. However,
actual exposure data will still be needed to provide solid estimates for exposure and
concomitant risk assessment. These, the real or simulated exposure studies are the
focus of this chapter. Recent developments with respect to measurement devices and
methods will be discussed here only briefly.
13.2 MEASUREMENT DEVICES
In general, devices used to assess exposure to nanomaterial or nano-size aerosols
can be subdivided into devices that monitor (on-line) a chemical substance or aerosol
by “near or quasi” real-time detection and devices that sample (time-aggregated)
chemical substances or aerosols on a substrate, followed by off-line analysis.
A suite of real-time devices are already available (Kuhlbusch et al. 2011), and
quite recently Asbach et al. (2012a) compared the performance of five different
real-time portable and battery-operated nanoparticle monitors measuring particle
number and surface area concentrations. Furthermore, Kaminski et al. (2013) inves-
tigated the comparability of mobility particle sizers and diffusion chargers. These
investigations are needed to allow the assessment of exposure related measurements
and assessments. Also, new devices have been developed and are likely to become
available on the market in the near future. For example, additionally to the estab-
lished real-time handheld devices, a device has become commercially available that
provides estimates of the surface area of the aerosol fraction deposited in the gas-
exchange region (Fierz et al. 2011). Another example of new developments is the
extension of the usability domain of existing devices. In addition to the currently
available stationary monitors using a DMA with a radioactive source as a bipolar
charger for size-resolved measurement of nanoscale particles, a number of devices
came up with a nonradioactive charger, Naneum Nano-ID NPS500 a proprietary
Corona unipolar charger, whereas TSI model 3087 uses bipolar diffusion charging
using soft X-ray. Within the recently concluded NANODEVICE project * interesting
near-market prototype real-time devices have been developed that (a) reduce size
and weight of existing device concepts that afford portability (and could be used
in a position closer to the receptor) and (b) increase the size ranges for both the
* www.nano-device.eu.