Chemistry Reference
In-Depth Information
The ensemble approach should also be further investigated as a way to
improve PM estimates. The Air Quality Model Evaluation International Initiative
(AQMEII—
http://aqmeii.jrc.ec.europa.eu/aqmeii2.html
)
is developing and testing
innovative model evaluation methodologies, focusing on ensemble, to improve
knowledge about relevant processes and to increase confidence in model perfor-
mance for better support of policy development.
Exposure modelling is a promising approach to exposure assessment, using
ambient air concentration modelling and the respective spatial and temporal distri-
bution, combined with population statistics, to get a statistical assessment. Aiming
at personal exposure information may become more accurate, using traffic models'
information on optimised daily trips (work, school, shopping) or even tracking
individuals mobile phone positions. Technology for exposure assessment is avail-
able; it is a matter of costs, data handling and data privacy regulations to access
such information. Anyway, a statistical assessment may prove sufficient for many
purposes.
Indoor environments are (in the absence of indoor sources) assumed to be
much less exposed to PM than outdoor air, due to the filtering effect of the
building. Nevertheless, some studies indicate that high indoor values are also
found [
28
]. Still, data show that ambient concentration levels reflect also the
temporal variation that is seen indoors, at least for PM. In this sense, the use of
ambient data as a proxy for the overall exposure has to be further analysed, since
it can introduce high inaccuracy in exposure calculations. How can the exposure
to indoor sources (cooking, cleaning, candle lights, smoking) be assessed and
what are the health implications of those sources are still questions to investigate,
taking into consideration PM outdoor-indoor penetration and the dependency
between lifetime indoor and the particles size, composition, physical properties
(e.g. volatility, hygroscopicity) and removal processes (absorption/adsorption
onto indoor surfaces). Moreover, it is clear that the fraction of time people
spend indoors changes between seasons and between places (especially northern
vs. southern Europe) and also depends on work habits that may change with time
(mechanisation of outdoor labour, but also leisure activities). Finally, influence of
the outdoor environment to indoor air quality or the indoor particle formation will
strongly depend on age and cultural habits, partly again triggered by environmen-
tal conditions. Together with the need to look into other metrics than PM alone,
this indicates the importance of better understanding the extent people are
exposed to particulate matter - with exposure as the potential to inhale and retain
a certain dose of material.
6 Final Comments
Air quality numerical models are useful tools for the mapping of PM, once the
monitoring networks are able to assess the air quality in single stations, and not a
whole area of interest. Mathematical models which simulate the evolution of both
