Environmental Health Criteria 214

HUMAN EXPOSURE ASSESSMENT
Standardized methods are not available for collecting information
on hand-mouth contact. Several researchers (Charney et al., 1980;
Brunekreef et al., 1983; Bellinger et al., 1986) have administered
questionnaires to parents of toddler-age participants in order to
qualitatively characterize the frequency with which children suck
their fingers (i.e., usually, sometimes, never). Direct observation
may be better suited to capturing micro-level activities, but such
approaches have rarely been used in large-scale field studies owing to
the expense of following more than a few participants and because of
concerns that the observation process will lead to bias or alterations
in typical patterns. Video techniques have now made it possible to
record participant activities with less interference. Davies et al.
(1990), for instance, used video methods to obtain data on the number
of times 2 year olds put their hands and objects in their mouth while
in standardized play situations. Zartarian et al. (1995) used
videotape data to collect micro-level data on four young farm children
at play inside their homes to quantify dermal and ingestion exposure
to pesticides. As Zartarian et al. point out, however, researcher
presence may still have influenced the participants' behaviour.
Observation of children's hand-mouth contact also has been performed
in clinical settings (e.g., Madden et al., 1980). All of these
methods, however, share the limitation that they cannot quantify the
full variability in factors that influence hand-mouth contact. Indeed,
capturing this variability may not even be possible, as is discussed
in a subsequent section of this chapter. In the absence of information
on hand-mouth contact, several researchers have measured mineral
levels in children's faeces to estimate typical soil ingestion rates
(Binder et al., 1986; Calabrese et al., 1989, 1990). Such estimated
ingestion rates can then be used to model exposure in areas with
measured soil contamination levels.
For dermal exposure, questionnaires are most appropriate for
collecting categorical-type information, such as whether a person
performed a certain activity during a designated activity. The US
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