Field and Laboratory Measurements Related to Occupational and Consumer Exposures - Safety of Nanomaterials along Their Lifecycle - page 306

(20 nm-5 µm) 8 size classes, and (c) a sampler for aerosol fraction deposited by
diffusion in the anterior nasal region 5-400 nm (Cena et al. 2011) have been devel-
oped. From another angle the combination of near-real time size-resolved measure-
ment results with deposition models will also result in dose estimates. This has been
applied for consumer exposure scenarios, for example, Chen et al. (2010), Lorenz
et al. (2011), Quadros and Marr (2011), and has recently been introduced for worker
exposure scenarios (Koivisto et al. 2011, 2012b).
Studies conducted to assess exposure in source domains 1 and 2, that is, during
the production of nanomaterials, which include the synthesis and activities related
to harvesting, milling/grinding, packaging, and the downstream use of these materi-
als (usually in powder form) present a lot of data mostly from DRIs. This limits the
quantification of the exposure to the NOAA since no clear quantification is possible.
Survey-type of studies, for example, those conducted by NIOSH (Curwin and Bertke
2011; Dahm et al. 2012), tend to focus on risk assessment and risk management
(comparison with recommended reference value), and provide shift-based (mass)
concentrations. Most studies demonstrate potential for exposure to NOAA, however,
the amount of data is still limited to get a clear picture of the range of exposure and
its within (day-to-day) or between worker variation.
With a few exceptions, studies conducted to assess exposure in source domains
3 and 4, that is, scenarios with nano-enabled products such as sprays, or potential
for release during the use phase of products, are workplace (or consumer) scenario
simulated studies, which provide good information on relevant processes and deter-
minants of release. This type of data is important for exposure modeling.
Laboratory release measurements are here considered as complementary to field
exposure measurements since laboratory release studies indicate possible workplace
and production processes which may lead to exposure and flag the need for sys-
tematic assessments which should be linked to appropriate safety measures. The
conceptual model as developed by Schneider et al. (2011) is considered useful for
a systematic evaluation of the various emission and release processes over the life-
cycle of a manufactured nanomaterial. The first two source domains cover more or
less the potential for release during processes and activities related to the production
and downstream use of nanomaterials, whereas the last two source domains reflect
actual application of nano-enabled products and use scenarios (and partly end-of-
life scenarios), so they also include consumer exposure scenarios. Field studies have
focused on the first two source domains, whereas the vast majority of data for the last
two source domains are generated in experimental studies.
Despite the increased number of data it is still difficult to draw general conclusions
from individual (and sometimes small scaled) studies whether there is significant
workplace exposure to NOAA. Larger surveys, for example, the NIOSH studies by
Curwin and Betke (2011) and Dahm et al. (2012, 2013), however, enable more robust
conclusions, as in these studies the exposure levels were evaluated with respect to a
(health-based) recommended exposure level (REL). These studies show that for TiO 2
the shift averages did not exceed the REL, whereas they did (for some job titles) for
CNT/CNFs. The recently published NANOSH study, which included 19 enterprises
in Europe, evaluated the results of activity-based measurements using a decision
logic, where the results of all types of measurements were combined (Brouwer et al.