Environmental Engineering Reference
In-Depth Information
generic models. Oomen and Lijzen (
2004
) reviewed studies carried out with per-
sonal sampling devices, and concluded that a dust concentration of 60
g/m
3
is
probably representative of moderately crowded places such as homes, whereas a
value of 100
μ
g/m
3
is probably more representative of crowded places such as class-
rooms. In a study by Janssen et al. (
1998
), outdoor concentrations (mean PM10 of
41.5
μ
g/m
3
), but these
levels underestimated adult exposure measured with personal devices (mean PM10
of 61.7
g/m
3
) exceeded indoor concentrations (mean PM10 of 35.0
μ
μ
g/m
3
). For children, mean indoor PM10 levels in classrooms (81-157
μ
g/m
3
). The personal samples showed
the same levels as the classrooms (mean value 105
g/m
3
) were higher than outdoor levels (30
μ
μ
g/m
3
). The studies reviewed
by Oomen and Lijzen (
2004
) showed that indoor dust levels are dependent on the
number of people in a room and on the activity levels, therefore dust levels are likely
to be higher when children are present. Dust levels were also dependent on height
above floor level (Beamer et al.
2002
), and children are exposed to higher amounts
of PM10 than adults in the same room.
μ
11.6.3.2 Fraction of Dust from the Contaminated Site
The fraction of material with mineralogic origin in dust is between 6 and 25%
(Putaud et al.
2003
) of the total amount of dust. Resuspended particles can account
for about half of the total weight (Hedberg et al.
2001
), though a large fraction of
these particles may be resuspended from road surfaces.
In the Swedish model for generic Soil Quality Standards, the annual average
value for dust concentration from a contaminated area in outdoor air is estimated
to be 5
g/m
3
,
by assuming that up to half of the PM10 concentration has a mineralogic origin,
and that 50% of the material of mineralogic origin is derived from the contaminated
area. The resulting concentration is assumed to be reasonably conservative. This
assumption is supported by model calculations of PM10 emissions from soil at three
places in Sweden (RIVM-VITO
2006
).
g/m
3
based on an urban background PM10 concentration of 20
μ
μ
11.6.3.3 Concentration of Dust in Indoor Air
The concentration of dust in indoor air is assumed to be 75% of the outdoor concen-
tration, based on the fact that the PM2.5 fraction (which is about 75% of the PM10
size fraction) is the fine fraction which is transported to indoor air.
Oomen and Lijzen (
2004
) reviewed estimates of the relative contribution of exte-
rior soil to house dust. Estimates from different articles ranged from > 80% to 8%,
depending on a wide variety of site-specific factors and methodological approaches.
The US EPA (
2002b
) uses a default value for the contribution of soil to indoor dust
of 70% in the IEUBK (Integrated Exposure Uptake BioKinetic) model which is
used to predict the risk of elevated blood lead levels in children who are exposed
to environmental lead from many sources. The value of 70% is based on empirical
relationships between soil and dust lead concentrations. Oomen and Lijzen (
2004
)
suggest that house dust can contain between 30 and 70% soil, and that estimates in
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