Civil Engineering Reference
In-Depth Information
outdoor ones, so WHO guidelines for Air Quality (WHO
2005
) recommendations
are applicable. There is little evidence to establish a safe threshold value below
which there is no adverse health effect derived from the exposure to PM. The
report of the US EPA on PM Health Effects (Lippmann et al.
2003
) suggests that
effects are different depending on the particle size and chemical composition. The
values set by the WHO guidelines were shown in Table
2
, for long-term effects as
annual means and short-term effects as 24-h mean values. Concentrations in Fig.
4
correspond to average values of the overall sampling period, but it may be stated
that guideline values for PM
2.5
(annual average of 10 lg/m
3
and daily mean
average of 25 lg/m
3
) are frequently exceed indoors. Otherwise, in developing
countries, PM concentrations are approximately 10-20 times higher than the
values quoted in WHO IAQ guidelines, as a result of the use of open fires for
cooking and heating purposes (WHO
2005
).
2.6 Polycyclic Aromatic Hydrocarbons
Polycyclic aromatic hydrocarbons (PAHs) are a group of over 100 chemicals
containing two or more fused aromatic rings. Lighter PAHs, with two and three
rings, occur in the air predominantly in vapour phase, whereas heavier PAHs, with
five rings or more, are mainly bound to particles (WHO
2010
). The majority of
particle-bound PAHs are found on small particles (PM
2.5
). Benzo[a]pyrene
(B[a]P), classified as carcinogenic to humans by the IARC, is used as a marker for
total exposure to PAHs.
Different health effects of each PAH complicate the estimation of the total
exposure risk, which is measured in terms of contribution of B[a]P to the car-
cinogenic potential of the mixture. PAHs are not limited in indoor air, and in
Europe, benzo[a]pyrene is the only PAH regulated in ambient air under Directive
2004
/107/EC. Table
5
shows the IARC classification of some PAH, selected from
European and US EPA lists and their IARC classification. In addition to individual
PAHs, IARC has also classified some activities emitting PAHs as carcinogenic to
humans, such as emissions from household combustion of coal (IARC
2013
).
PAHs are formed during incomplete combustion of carbon-containing matter at
high temperature (Nikolau et al.
1984
). ETS (Liu et al.
2001
) and fireplaces using
wood (Delgado-Saborit et al.
2011
) have been reported to be the main contributor
to PAHs indoors. Other indoor sources of PAHs are cooking, and incense and
candle emissions (Levy et al.
2002
; Ott and Siegmann
2006
). Indoor activities are
the main factor affecting indoor concentrations of PAHs, but sorption on building
materials and re-emission have been reported, and outdoor contribution may also
be considered (Li et al.
2005
). Main outdoor sources of PAHs are related to motor
vehicle emissions, domestic heating and industrial emissions such as power
generation plants, waste incinerators and open burning (Ravindra et al.
2008
).
Fluoranthene, pyrene and phenanthrene, all of them not classifiable as carcin-
ogenic to human, are the most abundant PAHs in ambient air, but the one
