Chemistry Reference
In-Depth Information
ENPs are emerging class of airborne nanoparticles having a main impact on the air
quality of indoor environments; these are unintentionally released into the ambient
environment during the manufacture (commercial or research), handling, use or
disposal of nanomaterials integrated products. Their physical and chemical
characteristics differ from other nanoparticles produced through traffic [
4
]. The
health consequences of their inhalation are not yet well known. A number of studies
have reported their number concentrations and size distributions in workplaces but
their concentrations in ambient urban environments are largely unknown and
warrant further research. Adequate methods have yet to be developed to quantify
them in the presence of nanoparticles from other sources.
Closer inspection of the PNC studies at various European locations indicates a
factor of ~2.4 differences between the overall average PNCs at roadside and
urban background locations. As expected, roadside PNCs exhibit higher
concentrations and up to a factor of 14 differences between the PNCs observed
at different roadside locations. Such a difference is nearly one-third (i.e. ~5 times)
of roadside PNCs for urban background sites. Sites in Birmingham and
Zurich appear to show highest PNCs among all the
roadside
sites in Europe
while Antwerp site seems to be the cleanest one among all other sites (Fig.
3
).
However, changes in concentrations over time complicate such cross-sectional
inter-comparisons. Among the reviewed European locations, Zurich and Prague
seem to show the most and the least polluted
urban background
sites, respectively
(Fig.
4
).
Deposition doses in the human respiratory system were estimated based on the
roadside PNCs in various locations. These showed the similar trend to the
roadside PNCs since the dose estimates did not take into account the size
distributions of particles at each site. Average deposition doses over all
the
10
10
h
1
for male subjects,
considered locations were found to be 3.61
0.17
10
11
h
1
) for site at Birmingham
where the study was carried out along the roadside about 15 years ago (i.e. in
1996-1997).
Nanoparticle emissions are progressively being controlled at source in Euro-
pean countries through the Euro-5 and Euro-6 emission standards. However, there
are currently no air quality regulations for airborne nanoparticles available in any
part of the world for controlling exposure at the receptor. As discussed in various
sections of this review chapter, there are still a number of practical and technical
constraints to overcome before any regulatory framework for atmospheric
nanoparticles can be put in practice. Some of the key additional challenges with
respect to emerging novel pollutants such as ENPs may include: (1) quantification
of the mass and number concentrations of ENPs in the presence of nanoparticles
from other sources such as traffic and (2) establishing exposure-response
functions for human health effects of different
with exceptionally high values (1.61
0.08
types of nanomaterials upon
inhalation.
Acknowledgements Prashant Kumar thanks the volume editor, Dr. Mar Viana, for inviting him
to write this chapter.
