Environmental Health Criteria 214

HUMAN EXPOSURE ASSESSMENT
basket survey based on heavy metal and pesticide data measured in
samples of 234 different ready-to-eat food products selected to be
representative of over 4000 foods common in the diet of residents in
the USA, and the results of national food consumption surveys
(Pennington, 1992). However, more commonly total diet (market basket)
studies consider smaller food groups rather than individual foods (UK
MAFF, 1985). The main advantage of the total diet (market basket)
approach for estimating exposure is the ability to monitor trends
without burdening study participants. The total diet approach allows
data from separate studies of food consumption and contaminant
residues to be combined (e.g., Tomerlin et al., 1996). Moreover, this
approach allows analytical chemistry resources to be directed to the
foods that are most likely to yield the greatest exposure (e.g., the
foods consumed in greatest amounts and foods that are likely to
contain the highest residue concentrations). Such foods may be
indicated by information available from existing data such as the
GEMS/Food (WHO, 1978, 1997c) and the US TDS (Pennington & Gunderson,
1987).
However, this method cannot be used for all contaminants. This is
because the analysis of food groups may be too expensive for some
contaminants and may not be feasible for others. Analytical methods
may not be sufficiently reliable, the limit of detection may be too
high or the grouping of the foods (compositing) may decrease the
likelihood of finding the source of the contaminant. Analysis of
individual food products affords a detailed examination of contaminant
levels in specific commodities -- either raw, processed or prepared.
Sampling may be designed to characterize geographic and temporal
variability of contaminant levels that may be a result of varying
application rates of pesticides, natural levels of elements (e.g.,
heavy metals), climate and other factors. In addition, samples can be
collected at all steps in the process from field to consumer thereby
providing insight into the sources and fate of contaminants in food.
Further information on the strengthens and limitations of each of
the approaches described above have been published in the
comprehensive Guidelines for the Study of Dietary Intake of
Chemical Contaminants (WHO, 1985a).
7.4.3 Food consumption
The FAO/WHO Consultation on Food Consumption and Exposure
Assessment of Chemicals (called Exposure Consultation) reviewed
current methodology for food additives, contaminants, pesticides,
veterinary drugs and nutrients. The Exposure Consultation agreed to
expand and revise the regional diets presently used by the GEMS/Food
for pesticides and recommended that this consumption data can be used
for estimate dietary exposure to certain other chemicals. The regional
diets will be based on 1990-1994 FAO Food Balance Sheets which reflect
a country's amount of raw commodities for consumption, and may not
necessarily refer to foods in the forms people consume them. Waste at
the household or individual level is not usually considered.
Major methods for determining food consumption at the national
levels were identified as population-based, household-based and
individual-based. The report from a FAO/WHO consultation on the
preparation and use of food-based guidelines (FAO/WHO, 1996) gives
more information on food consumption study designs. The Exposure
Consultation supported the concept that an improvement in dietary
http://www.inchem.org/documents/ehc/ehc/ehc214.htm
Page 133 of 284
6/1/2007