Report of Workshop on the Significance of Excursions of Intake above the ADI

Abstract

The acceptable daily intake (ADI) for humans was originally developed by the Joint FAO/WHO Expert Committee on Food Additives (JECFA) and defined as "an estimate of the amount of a food additive, expressed on a body weight basis, that can be ingested daily over a lifetime without appreciable health risk." JECFA has not provided any firm guidance on how to evaluate excursions of intake above the ADI, but WHO in 1987 stated that "because in most cases, data are extrapolated from life-time animal studies, the ADI relates to life-time use and provides a margin of safety large enough for toxicologists not to be particularly concerned about short-term use at exposure levels exceeding the ADI, providing the average intake over longer periods of time does not exceed it." In discussing short-term intakes in excess of recommended limits, JECFA in 1989 concluded that short-term exposures to levels exceeding the provisional tolerable weekly intake (PTWI) for a contaminant is not a cause of concern, provided the individual's intake averaged over longer periods of time does not exceed the level set. JECFA also stated that it was impossible to make a generalization concerning the length of time during which intakes in excess of the PTWI would be toxicologically detrimental. Any detrimental effect would depend upon the nature of the toxicity and the biological half-life of the chemical concerned. JECFA considered intakes of food additives in excess of the ADI less likely to occur and easier to control than in the case of contaminants which are allocated either a PTWI or a tolerable daily intake (TDI). The ILSI Europe Acceptable Daily Intake Task Force together with the Food Chemical Intake Task Force initiated a workshop which took place April 21-23, 1998, in Milan, Italy, in order to help identify what information would be needed, with what precision, and what is already available to evaluate the significance of excursions of intake above the ADI. The specific aims of the workshop were to address the following questions: By how much can the ADI be exceeded? For how long can excursions above the ADI be tolerated with respect to chronic toxicity, accumulation, and mechanisms of toxicity? What methods should be used to estimate intakes so that the estimates are relevant to the ADI? Do the same principles apply to contaminants that have TDI or PTWI values?