Environmental Health Criteria 214

HUMAN EXPOSURE ASSESSMENT
exposure assessments can be achieved by refining any combination of
the contributing elements: food consumption data, food chemical
concentration data or the method used to combine the two. This allows
the risk assessor a greater flexibility in selecting cost-effective
approaches to refine dietary exposure assessments using the resources
available (WHO, 1997c).
The five basic approaches discussed by the Exposure consultation
for describing the diet of individual people are:
* food record/diary survey
* 24-h recall
* food frequency questionnaire
* meal-based diet history
* food habit questionnaire (WHO, 1997c).
The 24-h recall is a widely used dietary assessment method and is
utilized in many exposure-related studies including the National
Health and Nutrition Examination Survey conducted by the US Centers
for Disease Control and Prevention (Witschi, 1990).
7.4.3.1 Food diaries
Food diaries are detailed descriptions of types and amounts of
foods and beverages consumed, meal by meal, over a prescribed period,
usually 3-7 days. Food diaries and recalls may be presented in
numerous formats or combined with food models and weighing procedures
to characterize serving size more accurately; however, regardless of
the specific details, dietary recording places a substantial burden on
the subject (Witschi, 1990).
7.4.3.2 24-h recall
The short-term nature of the 24-h recall and the facility to
consider meal occasions or daily consumption from diary surveys make
this method ideal for assessing exposure to substances that can give
rise to acute health effects, such as the cholinesterase-inhibiting
organophosphate and carbamate pesticides. Diary methods may be used
for assessment of long-term exposure but the underlying assumption is
that the food consumption is representative of usual habits.
Probabilistic approaches can be useful to predict consumption and
resulting exposure over longer periods of time.
7.4.3.3 Food frequency questionnaires
Food frequency questionnaires (FFQs) are a standard tool for
characterizing food intake over extended periods of time. A food
frequency questionnaire consists of two basic components: a list of
foods and a frequency response section for respondents to indicate how
often a specific serving size of each food is consumed (Table 28). The
underlying principle of the food frequency approach is that average
long-term diet, for example, intake over weeks, months or years, is
important rather than intake on a few specific days. This may not be
true for all contaminant-health effect combinations (e.g., acute and
reversible effects such as cholinesterase inhibition); however, it is
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