Environmental Health Criteria 214

HUMAN EXPOSURE ASSESSMENT
the most comprehensive information on time allocation, sequencing, and
frequency. Real-time diaries are particularly useful when it is
important to know the time of day during which each activity was
performed (e.g., the amount and location of exercise in the morning
versus the afternoon when ozone levels tend to be higher).
Two diary formats are common for collecting time-activity data:
the open-ended style requires participants to describe their exact
activity (see, for example, the instruments described in Akland et al.
(1985), Johnson (1989), and Jenkins et al. (1992)), whereas the
close-ended format (Fig. 18) involves simply checking the appropriate
microenvironment for the given time of day (see, for example, the
instruments used in EXPOLIS (Fig. 18) (Jantunen et al., 1998) or those
described by Schwab et al. (1990) and Samet et al. (1992). Several
researchers are developing electronic monitors to supplement diaries
by detecting whether a participant is indoors or outdoors, a key
parameter for assessing exposure to air pollutants (e.g., Hinton,
1990; Moschandreas & Relwani, 1991; Waldman et al., 1991b).
Interviewer-administered questionnaires that ask participants to
recall frequency and duration of time spent in specific activities
during either the previous or typical day, month, year or age-period
(i.e., usual activity patterns) also have been used to collect time
allocation measures, microenvironmental parameters and exposure
surrogates. Juster et al. (1985a) points out that data collected in
this fashion are most accurate when the survey focuses on activities
that are done frequently or on a routine basis (e.g., the daily
commute to work). Questionnaires that take the form of checklists are
also particularly useful when the researcher is only interested in
certain well-defined activities. Questions to recall activity patterns
over a long period may refer to defined age groups and/or to each
residential location lived in (see Fig. 19). In environmental exposure
studies, information on the proximity of the study participant to
http://www.inchem.org/documents/ehc/ehc/ehc214.htm
Page 86 of 284
6/1/2007