Dependence of dietary intake estimates on the time frame of assessment

Food chemical risk management needs, among other things, assessment of expo sure. For dietary intake food consumption surveys are the data source to be used. One complicating factor in the usage of these data is the dependence of dietary intake estimates on the time frame of assessment. Central to th is time dependence is the within-subject variation regarding the usage of f ood products and, as a consequence, the intake of chemicals. Within-subject variation is mostly as large as or larger than between-subject variation. Expressed per kilogram body weight, average (total) variation in intake var iables depends on the age group, with variation usually being greater at yo unger age, most likely as a result of the higher intake levels at that age. Combination of age groups results in an increase in between-subject variat ion, and correction based on the figures for the total population will be t oo small. Ideally, exposure data for all days of one's life should be avail able to assess lifetime exposure. Since information on all these days is no t an attainable and. practical option, and not an option to strive for eith er, the most recent available data should be used that can be extended with simulation studies to anticipate future developments, The present food con sumption surveys available in European countries are based on data that var y from 1 day (24-h recall and dietary record) to habitual intake (dietary h istory and food frequency). The data of a survey based on I day refer to 0. 004% of an average lifetime of 70 years. Based on the demographic picture o f the population, a reasonable approximation of lifetime intake can be obta ined. The proportion of users and the consumption level. among users depend on the time frame of assessment, especially for irregularly consumed produ cts. Usage of the concept of "users only" overestimates lifetime exposure o f the population, the extent of overestimation depending on the duration of the survey. The likelihood that all consumers have been exposed to a chemi cal once during a lifetime period is realistic in the sense of the best app roximation of reality. As a result of this assumption all exposure assessme nts will have a similar point of departure and the dependence of the result s on the food consumption method will be reduced.