Acceptable daily intake, also known simply as ADI, refers to the maximum amount of a substance such as a pesticide or food additive that a healthy person can ingest from food or drinking water on a long-term, daily basis without any harmful effects. ADI is measured as the mass (in milligrams) of a substance per kilogram of body weight per day and comes from extensive research. Substances in food include not only additives, but any substance that might come into contact with the food during packaging and handling, like coatings, adhesives, and sealants.
Determination of ADI was first suggested in 1957 by the Council of Europe and supported by the U.N. Joint Food and Agriculture Organization/World Health Organization Expert Committee on Food Additives. The purpose was to establish uniform worldwide safety standards. Many government food safety regulating bodies, including the U.S. Food and Drug Administration, currently recognize ADI standards.
Acceptable daily intake is established after toxicology tests on animals at several doses. To determine ADI, a substance is assigned a concern level of I, II, or III. Level I is the lowest estimated risk, while Level III substances are highest estimable risk. Tests are administered based on the concern level of the substance. Level III substances require more extensive testing than Level I substances.
A no observable effect level is determined from the results of the testing. If multiple results are determined from several studies, the lowest NOEL is used. A factor of 100 is used to account for differences between humans and animals, and to account for differing sensitivity levels between individuals.
The resulting acceptable daily intake indicates the maximum safe level of ingestion for a healthy adult who weighs 132 pounds (60 kilograms). Adjustments should be considered for people who do not fit this category, like the elderly, the sick, infants and children. The factor of 100 can partially account for these differences, as well as differences in sensitivity. It should be noted that ADI only determines safety, not a level of toxicity, and can be exceeded safely for short periods. The ADI should not be taken as an absolute number, but as a recommendation subject to change if new information becomes available.
Some food substances are considered contaminants. For these substances, a separate measure of tolerable daily intake is determined. Contaminants are considered substances that have no reason to be in food, unlike food additives, pesticides, or veterinary drugs.