Environmental Engineering Reference
In-Depth Information
Fig. 2
Spatial distribution of total intake fraction for benzene from mobile sources in 2005.
Helsinki city centre is marked with the
black ellipse
Table 1
Intake fraction by inhalation in Hämeentie Street (2000)
Breathing rate
(m
3
/day)
Time of
exposure (days)
Groups
No. of people
iFi
Inhabitants
1
176
0.56
1.6 E−05
Working and costumers
1
113
0.37
2.0 E−05
In traffic
1
20,380
1.04 E−04
1.1 E−06
Total iF
3.7 E−05
with a total intake fraction for these 129 people of 1.0 × 10
−8
. If we extrapolate from
the 129 EXPOLIS people to the working-age population (i.e., by multiplying this iF
with the ratio of the total working-age population within the area to the EXPOLIS
population,
[3]
), we estimate a population intake fraction of 3.9 × 10
−5
. The intake
fraction values computed using the EXPAND model and based on EXPOLIS data are
not directly comparable, as the location of the populations and the years considered
are different, and due to methodological differences. However, they both provide
useful information about the patterns of exposures across space and individuals, and
the results obtained by the two methods are fairly similar.
In a densely trafficked street canyon, such as the segment of Hämeentie considered
in this study, about 40 mg/g of benzene emitted on that road is inhaled by the people
living, working, and passing through that road segment. It can be seen that due to the
longer amount of time spent in the area, the intake fraction for residents is largest
and the in-traffic intake fraction is smallest (Table
1
).
