Environmental Engineering Reference
In-Depth Information
8.1 Growing Concerns About Indoor Air Pollution
As a result of the ongoing urbanisation of the Western world, around 80 % of
people now live in urban areas, where around 90 % of time is spent indoors
(Newton 2001 ; Environment Australia 2003 ). The quest for sustainable urban
communities must therefore include the achievement and maintenance of a healthy
'building ecology'. Thus urban air pollution (UAP) has become a worldwide
health concern. Ninety per cent of UAP comes from fossil fuel emissions, com-
prising a mixture of carbon dioxide (CO 2 ) and monoxide (CO), nitrogen oxides
(NO x ), sulfur oxides (SO x ), volatile organic compounds (VOCs), ozone and fine to
very fine particulate matter (PM10 and PM2.5).
Global healthcare and associated costs due to outdoor air pollution have been
estimated at US$828 trillion for developed countries, while indoor air pollution costs
for these countries is likely to be just under US$90 trillion (Hutton 2013 ). Health
costs associated with indoor air pollution may be as high as US$9.4 billion in the USA
alone, leading to as many as 150,000 mortalities per year (Guieysse et al. 2008 ).
The air quality of indoor spaces has now become a dominant heath concern
(Brown 1997 ;WHO 2000 ; Environment Australia 2003 ). Indoor air quality (IAQ)
has been designated as a significant health concern in both the USA and Europe
(Morey et al. 2001 ; Bernstein et al. 2008a ). Although not generally recognised,
indoor air pollution is almost always higher than outdoors. This is because as
outdoor-sourced contaminated air enters through natural or mechanical ventilation
systems, it mixes with indoor-sourced pollutants, in particular VOCs outgassing
from synthetic furnishings, finishes, paints, solvents and other materials derived
from petrochemicals (Environment Australia 2003 ; Sakai et al. 2004 ; Barro et al.
2009 ; Chan et al. 2009 ), and higher CO 2 concentrations produced by human
respiration and gas appliances (Norbäck and Nordström 2008 ). The tendency of
buildings constructed since the worldwide oil crisis in the 1970s to be sealed
against the outside environment and rely wholly on mechanical ventilation for air
replenishment has exacerbated problems associated with pollutant concentration in
indoor air. This issue is discussed further in Sect. 8.2 . Unless or until such time as
a return to primarily natural ventilation becomes the norm, there is a critical need
to develop means of maintaining a habitable indoor environment, whilst simul-
taneously improving building energy use and lowering greenhouse gas emissions
in an increasingly energy aware world. Hence it would appear that biological,
botanical and biotechnological approaches to solving this growing problem are the
most promising avenues to follow.
8.2 Current Practice
Replacing contaminated indoor air with outdoor air by increasing building ven-
tilation rates is the simplest and probably most effective means of improving IAQ.
A key reason that IAQ is increasingly becoming a major concern is the increasing
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