Estimating acute dietary intakes of chemicals.

In some cases a single dose above an acceptable daily intake could elicit an adverse effect. In other cases a cumulative dose over several days may be necessary before an effect is expressed. Estimates of acute intake must relate to what is known about the toxicokinetics of the substance, in relation to the toxicological studies associated with the relevant end point. This is because estimates of intake can vary considerably over even a few days in some circumstances. Acute reference doses should therefore be qualified by an exposure interval. Default values can introduce considerable conservatism into intake estimates. Techniques for estimating acute intakes are very varied. They can range in complexity from conservative screening methods to sophisticated techniques designed to simulate real situations. Monte Carlo models allow for the distributions of chemical concentrations and food consumption patterns to be taken into account. For acute dietary risk assessments very high upper percentile cutoffs are sometimes applied, even as high as 99.9%. However, assumptions applied in such methods can lead to misleading results. Great care must also be used when interpreting such statistics because uncertainty and inaccuracy in the data increase considerably in the upper "tail" of the distribution.