Environmental Engineering Reference
In-Depth Information
Nearly all tracer element studies were conducted in the summer period, a time
when soil contact probably will be more frequent than in other periods of the year.
The majority of the soil and dust ingestion studies are of USA origin and assessment
of their applicability outside the USA is limited.
In addition to inter-individual differences in behaviour, a number of regional fac-
tors can influence soil and dust ingestion rates, thus leading to significant variation
within regions and even countries. Climate influences the time spent outside and the
possibility for soil contact (e.g., snow cover). The difference between urban areas
with almost no gardens and little green areas compared to rural areas where children
have free access to uncovered areas will influence ingestion. Also, the “dustiness” of
the playing environment will have a role in the potential for soil and dust ingestion.
Often, contaminated regions are more dusty because of emission sources, therefore
resulting in potentially higher ingestion rates.
The Biokinetic validation studies show that a certain set of soil/dust ingestion
rates predicts intake well for one contaminated site, but not for another. This can be
related to absolute ingestion rates, but also to differences in the contribution from
the various soil and dust compartments (garden soil, community soil, house dust,
school dust).
Although we can define both child-specific and regional factors that influence
soil and dust ingestion rates, the quantification of their influence still is difficult. The
results of the assessment of the scientific data constitute the basis for deriving default
values or distributions, whereas consideration of region- or site-specific information
could be used to modify default values.
6.3 Conclusions
Different methodologies for the derivation of soil and dust ingestion rates for use
in Human Health Risk Assessment are available, but all have their advantages and
disadvantages. Moreover, the collection of the information is time-consuming and
requires active involvement of experimental participants. Therefore, the number of
studies is limited and the number of participants per study is low, so that a decent
statistical analysis is difficult.
A first requirement for analysis of the studies is a clear definition of what is meant
by soil and dust. Then, the studies can be analyzed in the light of these definitions.
Human Health Risk Assessment for contaminated sites requires at least the con-
sideration of ingestion from outdoor soil and from soil-derived indoor dust. Tracer
methodology studies probably provide the most adequate estimates of soil inges-
tion rates, but are limited to short-term estimates and do not allow us to distinguish
between soil and dust. Hand-loading studies can be designed such that informa-
tion is collected for the relevant micro-environments, but the interpretation requires
assumptions about transfer parameters, as such, introducing substantial uncertainty.
At the moment, Biokinetic modelling studies can only provide estimates of ranges,
but are nevertheless useful as a complementary line of evidence.
Search WWH ::




Custom Search