Acute single value dietary exposure assessment¶
The short term (acute) exposure assessment is usually the exposure related to a consumption of food over a single day. MCRA applies in principle the IESTI equations as shown in EFSA PRIMo revision 3 (EFSA (2018)), but the equations are extended with a factor \(\mathtt{OF}\) to allow adaptation for an occurrence frequency lower than 1. So the inputs to the equations are not necessarily the same as used in PRIMo. For example, the large portion (\(\mathtt{LP}\)) and body weight (\(\mathtt{BW}\)) can be computed instead of just being standard values.
IESTI (International Estimated Short-Term Intake)¶
The IESTI (International Estimated Short-Term Intake) is calculated according to different equations depending on the unit weight of the raw agricultural commodity (RAC) and the unit weight of the edible portion (EP). The following cases are distinguished.
- Case 1
refers to commodities with unit weight of the raw agricultural commodity \(\mathtt{U}_{\mathtt{RAC}} ≤ 25\) g (e.g. walnuts, strawberries and peas. It is also used for meat, liver, kidney, edible offal, eggs and for post-harvest uses in cereal grains, oilseeds and pulses).
- Case 2a
for food product with a \(\mathtt{U}_{\mathtt{RAC}} > 25\) g, where the meal portion is \(>\mathtt{U}_{\mathtt{ep}}\) (unit weight edible portion).
- Case 2b
for food products with a \(\mathtt{U}_{\mathtt{RAC}} > 25\) g, where the meal portion is \(\leq \mathtt{U}_{\mathtt{ep}}\).
- Case 3
for food products that are usually bulked or blended before they are consumed (e.g. cereals, pulses, oilseeds and milk).
The calculations are as follows.
- Case 1
- Case 2a
- Case 2b
- Case 3
- New Case 1 and 3:
- New Case 2a and 2b
Parameters used in the equations
\(\mathtt{MRL}\): Maximum residue level for the RAC concerned (default in mg/kg);
\(\mathtt{STMR}\): Supervised Trials Median Residue for raw agricultural commodity (RAC) concerned (default in mg/kg);
\(\mathtt{CF}\): Conversion factor residue definition enforcement to residue definition risk assessment (calculated as the ratio of residues according to the residue definition for risk assessment divided by the residue concentration according to the residue definition for enforcement);
\(\mathtt{OF}\): Use Frequency of the raw agricultural commodity (RAC),
\(\mathtt{BW}\): body weight of the population related to the \(\mathtt{LP}\) (default in kg);
\(\mathtt{LP}\): Large portion reported (in kg/day) (97.5th percentile of eaters (or alternative percentile, depending on the number of reported eating occasions);
\(\mathtt{HR}\): Highest residue according to residue definition for enforcement in composite sample (default in mg/kg);
\(\mathtt{U}_{\mathtt{\mathtt{ep}}}\): Unit weight of edible portion (in kg), provided by the country from which the \(\mathtt{LP}\) was reported (or mean unit weight calculated from all available unit weight data, if no unit weight is available from the country matching the highest \(\mathtt{LP}\);
\(\mathtt{PF}\): Processing factor or peeling factor (calculated as the ratio of residues in processed/peeled product, divided by residue concentration in unprocessed/unpeeled product);
\(\mathtt{VF}\): variability factor, depending on the unit weight of the whole product \((\mathtt{U}_{\mathtt{RAC}})\), different default \(\mathtt{VF}\) are used in the calculations.
\((\mathtt{U}_{\mathtt{RAC}}) < 25\) g, the calculations are performed according to case 1 (\(\mathtt{VF}\) = 1).
\((\mathtt{U}_{\mathtt{RAC}})\) between 25 and 250 g: \(\mathtt{VF}\) = 7.
\((\mathtt{U}_{\mathtt{RAC}})\) greater than 250: \(\mathtt{VF}\) = 5.
In \(\mathtt{IESTI}_{new}\), a default \(\mathtt{VF}\) of 3 is used.
In case the empirically derived variability factors are available, the default \(\mathtt{VF}\) is to be replaced.
Alternative IESTI-styled assessments¶
If consumption survey data for a specific population are available, the \(\mathtt{LP}\) values in the IESTI equations may be replaced by statistics calculated from these data (at the consumed modelled food level).
If concentration monitoring data (retrospective) or concentration field trial data (prospective) are available, the \(\mathtt{MRL}, \mathtt{HR}, \mathtt{STMR}\) values in the IESTI equations may be replaced by statistics calculated from these data (at the consumed modelled food level).
In the current use of IESTI, the occurrence frequency (use frequency) \(\mathtt{OF}\) is assumed to be 1. In alternative assessments, a more realistic estimate may be used. Such an estimate could be derived for example as the highest occurrence frequency observed in a retrospective assessment for either the same substance or the same food.
IESTI special cases¶
For some foods, substances are applied after harvest, i.c. post-harvest use. For those combinations of food and substance, Case 1 should be used in the calculation. However, commodities with post-harvest use like cereal grains, oilseeds and pulses are typically bulked or blended (Case 3). To overrule Case 3, specify in table IESTISpecialCases the food and substance combination with ‘PostHarvest’ as application type. For those food and substance combinations with a unit weight of the raw agricultural commodity \(\mathtt{U}_{\mathtt{RAC}} ≤ 25\) g, Case 1 is applied. When substances are applied before harvest, i.c. pre-harvest use, Case 1 should be overruled by Case 3. Specify in table IESTISpecialCases the food and substance combination with ‘PreHarvest’ as application type. See also IESTISpecialCases table format.