Environmental Engineering Reference
In-Depth Information
Table 6.6
The age-specific
default soil/dust ingestion
rates recommended for use in
the Integrated Exposure
Uptake Biokinetic (IEUBK)
model for lead in children
Age groups (years)
IEUBK-model defaults (mg/d)
0-1
85
1-2
135
2-3
135
3-4
135
4-5
100
5-6
90
6-7
85
US EPA (
1999
)
Ingestion values from tracer studies using soil concentrations were interpreted
as ingestion of soil outdoors, soil used indoors to support plant growth and from
soil particles that have been tracked into the indoor environment. This is a different
interpretation than in US EPA (
2008
). Results based on Calabrese et al. (
1989
)were
left out, because Calabrese claimed in 2003 that these data overstate the soil inges-
tion rate. The result of the re-analysis of literature data was a set of selected soil
ingestion values that met the above-mentioned criteria. Mean values (
standard
deviation) were calculated, and these data were subsequently used for bootstrap-
ping. Parametric bootstrapping was performed on the lognormal distribution fitted
through the arithmetic mean from these studies. The distribution results in a mean
soil (combined outdoors and tracked indoors) ingestion rates of 63 mg/d (95%
±
=
81 mg/d) and a 95th percentile of 97 mg/d (95%
124 mg/d; Table
6.7
). The
authors applied a model developed by Bierkens and Cornelis (
2006
) that derives
ingestion rates for soil indoor and outdoor and dust from tracer study data, using
information on the fraction of soil in indoor dust and the ratio of ingestion indoors
compared to ingestion outdoors. This model results in a daily soil and dust ingestion
rate of 87 mg/d for children, which is slightly lower than the 100 mg/d proposed in
US EPA
2008
.
Van Holderbeke et al. (
2008
) estimated the mean soil ingestion for adults based
on the available tracer studies. The arithmetic mean daily soil (outdoors/tracked-
in) ingestion rates for adults range between 5 and 92 mg/d, taking into account the
background exposure. The arithmetic mean of all these values is 46 mg/d. When
=
Table 6.7
Statistical descriptors of the distributions for soil and dust ingestion by children from
1 to 7 years obtained using bootstrapping (mg/d)
Soil (outdoor and tracked-in)
Soil (outdoor) Dust (indoor) Soil and dust
Distribution of
arithmetic
mean
Distribution
of 95th
percentile
Arithmetic mean
63
97
39
45
87
Standard
deviation
11
16
95th percentile
81
124
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