Acute and chronic dietary exposure assessments
International estimated short-term intake (IESTI) and International Estimated Daily Intake (IEDI)
International Estimated Daily Intake (IEDI)
International estimated short-term intake (IESTI)
International Estimated Short-term Intakes (IESTIs) are assessed for a pesticide by the Joint FAO/WHO Meetings on Pesticide Residues (JMPR) when it has established (or intends to establish) an acute reference dose (acute RfD) for the pesticide. JMPR must also have recommended a proposed Maximum Residue Limit (MRL) for one or more commodities and have estimated Supervised Trials Median Residue values (STMRs) in those commodities that are bulked or blended.
The need for procedures for calculating short-term intakes was first discussed at an FAO/WHO consultation in 1995(1) and were initially described an FAO/WHO consultation held in Geneva in 1997(2). Subsequently, these procedures were refined, and continue to be refined, at meetings of JMPR(3) Unlike the GEMS/Food Regional Diets that are based on per capita consumption(4), short-term intakes are based on a large portion of a commodity that is consumed on a single day both by the general population and by children ages 6 and under. The large portion values are obtained from actual food consumption survey data for individuals identified as 97.5 percentile consumers of the commodity among eaters only.
In response to a request from the Codex Alimentarius Commission(5), data on the consumption of large portions of commodities by the general population and children ages 6 and under (Data set 1) were provided by Australia, France, The Netherlands, Japan, South Africa, Thailand, the United Kingdom of Great Britain and Northern Ireland (UK) and the United States of America (USA) as well as the age distribution and mean body weights for the relevant groups (Data set 2). In addition, data on unit weight and per cent edible portion (Data set 3) were provided by Belgium, France, Japan (unit weight only), Sweden, the UK and the USA. Data on large portion consumption of commodities, body weights and unit weights (including edible portion are used for IESTI calculations are compiled by GEMS/Food.
All Member States who have not already done so are requested to review their large portion databases in comparison to the values currently listed in the GEMS/Food Data set 1. If their 97.5th percentile consumption of any commodity in their countries exceeds the consumption presently listed, this should be reported to GEMS/Food. In such cases, the ages and mean body weights for the relevant population groups, as shown in Data set 2, should also be reported. In addition, countries with information on typical unit weights and per cent edible portion of those commodities listed in Data set 3 are encouraged to report these to GEMS/Food. Countries are invited to contact the GEMS/Food Manager (foodsafety@who.int) for guidance prior to submission of any data. The data sets are updated periodically as indicated on the various data sets.
Depending on the data on consumption, the IESTI for each commodity is calculated from the equation defined for each case, as described below. The following definitions apply to all equations:
- LP = highest large portion provided (97.5th percentile of eaters), in kg of food per day
- HR = highest residue in composite sample of edible portion found in data from supervised trials data from which the MRL or STMR was derived, in mg/kg
- HR-P = highest residue in the processed commodity, in mg/kg, calculated by multiplying the HR in the raw commodity by the processing factor
- bw = body weight, in kg, provided by the country for which the large portion, LP, was used
- U = unit weight, in kg, provided by the country in the region where the trials which gave the highest residue were carried out; calculated allowing for the per cent edible portion
- v = variability factor represents the ratio of the 97.5th percentile residue to the mean residue in single units. Default factors for various commodities are listed below
- STMR = supervised trials median residue, in mg/kg
- STMR-P = supervised trials median residue in processed commodity, in mg/kg
Case 1
The concentration of residue in a composite sample (raw or processed) reflects that in the large portion size of the commodity. This is assumed to be the case when the unit weight is < 25 g. This case also applies to meat, liver, kidney, edible offal and eggs.
IESTI = (LP * (HR or HR-P)) / bw
Case 2
The typical unit, such as a single piece of fruit or vegetable, might have a higher residue than the composite such as when a unit weight of a commodity is > 25 g. The variability factors, v, shown below are applied in the equations. When sufficient data are available on residues in single units to calculate a more realistic variability factor for a commodity, the calculated value should replace the default value of 3 for all commodities.
Note that the 2003 JMPR has proposed to use a variability factor of 3 for all commodities.
When data are available on residues in a single unit and thus allow estimation of the 97.5th percentile residue in a single unit, this value should be used in the first part of the equation for case 2a, with no variability factor, and the HR value derived from data on composite samples should be used in the second part of the equation. For case 2b, the estimated 97.5th percentile residue in a single unit should be used in the equation with no variability factor.
Case 2a
The unit weight of the whole portion is lower than that of the large portion, LP.
IESTI = (U * (HR or HR-P) * n+ (LP-U) * (HR or HR-P)) / bw
Case 2b
The unit weight of the whole portion is higher than that of the large portion, LP.
IESTI = (LP * (HR or HR-P) * n) / bw
Case 3
When a processed commodity is bulked or blended, the STMR-P value represents the probable highest concentration of residue. This case also applies to milk.
IESTI = (LP * STMR-P) / bw
A risk assessment for short-term dietary intake is conducted for each commodity-compound combination by expressing the IESTI as a percentage of the acute RfD. When the maximum residue level is recommended for a Codex commodity group (i.e. citrus fruit), intakes are calculated for individual commodities within the group. The selected commodities should include the one(s) that will lead to the highest intake.
The calculation of the dietary intake of fat soluble pesticides in meat is slightly different for mammalian meat and poultry meat. For mammalian meat, 20% of the meat large portion should be considered to contain residue at the concentration level in fat and 80% of the meat large portion should be considered to contain residue at the concentration level in the muscle with the trimable fat removed. For poultry, the percentages are 10% and 90% of the meat large portion for fat and muscle residues respectively.
The percentage of the acute RfD for the general population and for children are rounded to one significant figure for values up to and including 100% and to two significant figures for values above 100%. If the percentage is greater than 100%, the information provided to the JMPR does not allow confirmation that the short-term dietary intake of the residue in that commodity would be below the acute RfD.
References:
(1) WHO (1997) Guidelines for predicting dietary intake of pesticide residues. 2nd revised edition, unpublished Document WHO/FSF/FOS/97.7, Geneva.
(3) For JMPR reports see the JMPR Web site.
(4) WHO (1998). GEMS/FOOD Regional Diets. unpublished Document WHO/FSF/98.3. Geneva.
(5) CAC Circular Letter CL 1999/30-PR Part 3a