Environmental Health Criteria 214

HUMAN EXPOSURE ASSESSMENT
There are a number of methods for measuring estimating food
consumption and contamination. The method chosen will depend on the
information available, the population group of concern, whether acute
or chronic effects of the chemical are being expressed, the intended
use of the results and available resources. The reader is strongly
advised to refer to more comprehensive documents on dietary survey
methodology and dietary exposure assessment approaches.
8. MEASURING HUMAN EXPOSURE TO CHEMICAL CONTAMINANTS IN SOIL AND
SETTLED DUST
8.1 Introduction
This chapter is intended to provide the reader with important
concepts and a basic understanding of soil and settled dust sampling
so that effective sampling strategies can be designed to meet specific
research needs. Choices in sampling methods, sampling locations,
sampling areas and the sampling time of the sample collection may be
particularly important when the results are used for exposure
assessment purposes. For these methods to be used successfully, it is
important that the investigators understand the basic concepts behind
collecting soil and settled dust and the limitations of different
methods and strategies. Because this field of research is currently
evolving rapidly, it is recommended that researchers consult the
literature for new and complete information before designing a study
to measure toxic metals, pesticides, PAHs, other products of
incomplete combustion, fibres and biological matter. The most
appropriate method for sampling soil and settled dust depends on the
living conditions of the study population and the target contaminants.
The information in this chapter is therefore intended to provide
general guidance on approaches that might be taken.
Soil is a mixture of air, water, mineral and organic components
(Horne, 1978). The relative mix of these components determines to a
large extent the capacity of a soil for containing chemical
contaminants and the potential for it to be an important source of
exposure. Settled dust, which may be found outdoors or indoors, is
often a complex mixture of material from several sources. Outdoor
settled dust is material deposited on roadways, streets and other
paved surfaces. Indoor settled dust (house dust) is material deposited
on indoor surfaces such as floors, carpets and furniture. Chemical
contaminants present in indoor dust can originate from activities in
the home or can be tracked into the home from road dust, soil or work
sites (US EPA, 1991). Material present in soil, outdoor dust and
indoor dust may include clay, sand, bacteria, viruses, allergens,
products of incomplete combustion, environmental tobacco smoke, heavy
metals, pesticides, asbestos fibres, paint fragments, solvents, flame
retardants, cleaners, and residues from synthetic fibres, building
products and many other materials and pollutants (Robert & Dickey,
1995).
Unintentional ingestion of house dust, particularly for children,
may be a significant contributor to the total human exposure to many
potentially toxic substances, depending on personal living conditions
and frequency of contact with this media. Because children spend more
time in contact with soil and indoor surfaces than adults and have a
greater dose given the same exposure, these exposure pathways are
particularly relevant to children. For example, it is likely that
children's lead exposure from settled dust is an important
contribution to total lead exposure because of the past and present
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