csefh - Kinder-Umwelt-Gesundheit

corresponded to the 24 hour period from noon on
Monday to noon on Tuesday. Based on these
definitions, the food soil equivalent was subtracted
from the fecal soil equivalent to obtain an estimate of
soil ingestion for a trace element. A daily overall
ingestion estimate was constructed for each child as the
median of trace element values remaining after tracers
falling outside of a defined range around the overall
median were excluded.
Table 5-17 presents adjusted estimates,
modified according to the input/output misalignment
correction, of mean daily soil ingestion per child
(mg/day) for the 64 study participants. The approach
adopted in this paper led to changes in ingestion
estimates from those presented in Calabrese et al.
(1989).
Estimates of children’s soil ingestion projected
over a period of 365 days were derived by fitting lognormal
distributions to the overall daily soil ingestion
estimates using estimates modified according to the
input/output misalignment correction (Table 5-18). The
estimated median value of the 64 respondents' daily soil
ingestion averaged over a year was 75 mg/day, while
the 95 th percentile was 1,751 mg/day. In developing the
365-day soil ingestion estimates, data that were
obtained over a short period of time (as is the case with
all available soil ingestion studies) were extrapolated
over a year. The 2-week study period may not reflect
variability in tracer element ingestion over a year.
While Stanek and Calabrese (1995a) attempted to
address this through modeling of the long term
ingestion, new uncertainties were introduced through
the parametric modeling of the limited subject day data.
5.3.5.4 Calabrese and Stanek, 1992b - What
Proportion of Household Dust is Derived
from Outdoor Soil?
Calabrese and Stanek (1992b) estimated the
amount of outdoor soil in indoor dust using statistical
modeling. The model used soil and dust data from the
60 households that participated in the Calabrese et al.
(1989) study, by preparing scatter plots of each tracer’s
concentration in soil versus dust. Correlation analysis
of the scatter plots was performed. The scatter plots
showed little evidence of a consistent relationship
between outdoor soil and indoor dust concentrations.
The model estimated the proportion of outdoor soil in
indoor dust using the simplifying assumption that the
following variables were constants in all houses: the
amount of dust produced every day from both indoor
Child-Specific Exposure Factors Handbook
Chapter 5 - Ingestion of Soil and Dust
and outdoor sources; the proportion of indoor dust due
to outdoor soil; and the concentration of the tracer
element in dust produced from indoor sources. Using
these assumptions, the model predicted that 31.3
percent by weight of indoor dust came from outdoor
soil. This model was then used to adjust the soil
ingestion estimates from Calabrese et al. (1989). Using
an assumption that 50 percent of excess fecal tracers
were from indoor origin and 50 percent were from
outdoor origin, and multiplying the 50 percent indoororigin
excess fecal tracer by the model prediction that
31.3 percent of indoor dust came from outdoor soil,
results in an estimate that 15 percent of excess fecal
tracers were from soil materials that were present in
indoor dust. Adding this 15 percent to the 50 percent
assumed outdoor (soil) origin excess fecal tracer
quantity results in an estimate that approximately 65
percent of the total residual excess fecal tracer was of
soil origin (Calabrese and Stanek, 1992b).
5.3.5.5 Calabrese et al., 1996 - Methodology to
Estimate the Amount and Particle Size of
Soil Ingested by Children: Implications for
Exposure Assessment at Waste Sites
Calabrese et al., 1996 examined the hypothesis
that one cause of the variation between tracers seen in
soil ingestion studies could be related to differences in
soil tracer concentrations by particle size. This study,
published prior to the Calabrese et al. (1997a) primary
analysis study results, used laboratory analytical results
for the Anaconda, Montana soil’s tracer concentration
after it had been sieved to a particle size of