The acceptable daily intake (ADI) for humans was originally developed by th
e 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 ba
sis, that can be ingested daily over a lifetime without appreciable health
risk." JECFA has not provided any firm guidance on how to evaluate excursio
ns of intake above the ADI, but WHO in 1987 stated that "because in most ca
ses, data are extrapolated from life-time animal studies, the ADI relates t
o life-time use and provides a margin of safety large enough for toxicologi
sts not to be particularly concerned about shortterm use at exposure levels
exceeding the ADI, providing the average intake over longer periods of tim
e does not exceed it." In discussing short-term intakes in excess of recomm
ended limits, JECFA in 1989 concluded that short-term exposures to levels e
xceeding the provisional tolerable weekly intake (PTWI) for a contaminant i
s not a cause of concern, provided the individual's intake averaged over lo
nger 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. d
uring which intakes in excess of the PTWI would be toxicologically detrimen
tal, Any detrimental effect would depend upon the nature of the toxicity an
d the biological half-life of the chemical concerned. JECFA considered inta
kes 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 PT
WI or a tolerable daily intake (TDI). The ILSI Europe Acceptable Daily Inta
ke 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 wh
at is already available to evaluate the significance of excursions of intak
e above the ADI, The specific aims of the workshop were to address the foll
owing questions:
By how much can the ADI be exceeded?
For how long can excursions above the ADI be tolerated with respect to chro
nic toxicity, accumulation, and mechanisms of toxicity?
What method should be used to estimate intakes so that the estimates are re
levant to the ADI?
Do the same principles apply to contaminants that have TDI or PTWI values?