20th Australian Total Diet Survey
Appendix 5 Definitions and glossary of terms
In the process of estimating safe intakes and regulatory limits for pesticide residues and contaminants, the following terms are most commonly used.
Acceptable Daily Intake (ADI)
The Acceptable Daily Intake (ADI) for humans is defined as an estimate of the amount of a chemical that can be ingested daily over a lifetime without appreciable risk to health (WHO 2001c).
ADIs are set using information obtained from toxicological studies, including data from studies on various laboratory animals. From these studies, a No Observable Effect Level (NOEL) is established. The NOEL is the highest dose level that produces no observable toxic effect in the most sensitive test species and is expressed in milligrams per kilogram of body weight per day (mg/kg bw/day).
The ADI is derived by applying a safety factor to the NOEL. The safety factor takes into consideration the nature of the effect, differences between laboratory test animals and humans, and genetic variation in the human population. If any information on exposure in humans is available, usually from short to mid-term, this will be used to set the ADI. The unit for the ADI is milligrams per kilogram of body weight per day.
The ADIs for pesticides, as recommended by the Therapeutic Goods Administration (TGA), were used in this survey. These ADIs can also be found on the TGA website at www.health.gov.au/tga/chem/chem.htm . The ADIs used in this report are listed in Table 6 in Part 1 of the supplementary section. The body masses used for each age–gender category to compare the ADIs with the estimated daily intakes are listed in Table 4 in Part 1 of the supplementary section.
Limit of Detection (LOD)
The LOD is the lowest concentration of a chemical that can be qualitatively detected using a specified laboratory method and/or item of laboratory equipment (i.e. its presence can be detected but not quantified).
Limit of Reporting (LOR)
The LOR is the lowest concentration of a chemical that can be detected and quantified, with an acceptable degree of certainty, using a specified laboratory method and/or item of laboratory equipment.
Maximum Permitted Concentration (MPC) or Maximum Level (ML)
The Maximum Level (ML) (previously referred to as Maximum Permitted Concentration (MPC)), expressed as milligram per kilogram, is the limit placed on the level of a contaminant, such as a heavy metal, in food. An ML is set at the lowest level that is achievable with good practices, while taking into account likely intakes of the contaminant in comparison to the PTDI or PTWI.
MPCs are listed in Volume 1 of theFood Standards Codeand MLs are listed in Volume 2 of the Food Standards Code.
Maximum Residue Limit (MRL)
The Maximum Residue Limit (MRL) is the highest concentration of a chemical residue that is legally permitted or accepted in a food or animal feed. The MRL does not indicate the amount of chemical that is always present in a treated food but it does indicate the highest residue that could result from the registered conditions of use. The concentration is expressed in milligrams per kilogram (mg/kg) of the food or animal feed. If the MRL is exceeded then this indicates a likely misuse of the chemical. MRLs are not direct public health and safety limits but are indicators of whether an agricultural or veterinary chemical product has been used according to its registered use.
Although MRLs are not direct health measures, the toxicology of the chemical is taken into consideration when setting the MRL. An MRL is not recommended and the use of a pesticide not approved where the resulting residues from all foods may lead to exposures exceeding the ADI.
Generally, specific MRLs are not set for processed foods. For foods such as vegetables, fruits, meat and fish that undergo little processing before consumption, the MRL for the commodity can suffice for the food as consumed. In the case of a mixed food, the applicable MRL is calculated from the combined proportionate quantities of the ingredients of the mixed food and the MRLs that apply to these ingredients.
The MRLs allowed for residues in foods sold in Australia are listed in theFood Standards Code.
Provisional Tolerable Daily Intakes (PTDI) are upper limits that are set for substances that do not accumulate in animals and humans (WHO 2001c), PTDIs have been set for arsenic, copper, selenium, and zinc. Antimony has an oral reference dose (USEPA 1991).
Provisional Tolerable Weekly Intakes (PTWI) are set for substances, such as heavy metals, that are contaminants in food and are known to accumulate in animals and humans. PTWIs have been set for cadmium, lead, mercury and tin.
The unit of time for PTWIs is different to that used for ADIs and PTDIs. PTWIs use a one week time unit while ADIs and PTDIs use a one day time unit. Another difference is the term ‘provisional’, which is used in PTWIs and PTDIs in order to emphasize the paucity of safety data on contaminants. The levels of PTDIs and PTWIs are continually being re-evaluated.
The method for calculating a PTDI/PTWI for a contaminant is similar to that used for calculating an ADI for a pesticide. A NOEL is set and the PTDI/PTWI is derived from the NOEL using a safety factor. In the case of metals, there is often human epidemiological information, generally occupational exposure, on which NOELs can be based. Heavy metals have been recognised as poisons for centuries and many accidental poisonings have been recorded. Because heavy metal NOELs are generally based on known effects on humans, a lower safety factor than commonly used for food additives is therefore normally applied.
Tolerable levels are recommended by the Joint FAO/WHO Expert Committee on Food Additives. The PTDIs and PTWIs used in this report are listed in Table 7 in Part 1 of the supplementary section.
Recommended Dietary Intakes (RDI)
Recommended dietary intakes are “the levels of intake of essential nutrients considered…to be adequate to meet the known nutritional needs of practically all healthy people…” (NHMRC 2001b). RDIs are established based on the available scientific knowledge and take into account the variability in absorption and metabolism of the nutrients between individuals.
Refer to definition of PTDI/PTWI.
Part A | Part B | Part C Appendix 1 | Appendix 2 | Appendix 3 | Appendix 4 | Supplementary Information