Principle
The objective of the consumer risk assessment is to determine whether the pesticide residues in agricultural commodities (and drinking water) do not pose an unacceptable risk to consumers as a result of application as authorized under local conditions of use (that is, as recommended on the label and respecting pre-harvest intervals).
To assess whether the residue level expected to occur in commodities does not lead to unacceptable consumer risk, available residue data are combined with cultural dietary information to estimate potential residue intake by consumers, which is compared to toxicological reference values.
The toxicological reference values used in dietary risk assessment are the Acceptable Daily Intake (ADI) and the Acute Reference Dose (ARfD).
The Acceptable Daily Intake (ADI) is the estimate of the amount of a pesticide in food or drinking-water that can be ingested daily over a lifetime without appreciable health risk to the consumer, on the basis of all the known facts at the time of the evaluation. It is expressed in milligrams of the pesticide per kilogram of body weight.
The Acute Reference Dose (ARfD) is the estimate of the amount of a pesticide in food or drinking-water that can be ingested over a period of 24 hours without appreciable health risk to the consumer, on the basis of all the known facts at the time of the evaluation. It is also expressed in milligrams of the pesticide per kilogram of body weight.
Dietary intake of the pesticide is estimated by combining national or regional food consumption statistics with the estimated residues in food and/or drinking water.
The consumer is considered to be adequately protected when estimated long-term and short-term dietary intake of pesticide residues does not exceed the acceptable daily intake (ADI) and the acute reference dose (ARfD), respectively.
Applicability
The dietary risk assessment should be conducted whenever the pesticide is intended to be used on food crops.
A full dietary risk assessment may not be required if the same active ingredient has already been registered in the country on the same commodity or commodity group, and its dietary risk has already been evaluated. In such a case, a
comparison of GAPs may be sufficient to assess whether consumers are sufficiently protected.
A dietary risk assessment may be bridged if a relevant risk evaluation report is available from a reference country. Bridging residue assessments is further explained under
comprehensive residue evaluation.
Data requirements
The following data are needed for dietary risk assessment.
- Toxicological reference values: ADI and ARfD
- Residue estimates: Maximum Residue Limit (MRL), Supervised Trials Median Residue (STMR), Highest Residue (HR), processing factors (if applicable)
- Food intake estimates: national diet or regional cluster diet; large portion estimate for the relevant commodities.
Assessments
For chronic dietary risks, the following two-tiered assessment is generally conducted. The chronic risk assessments are done for all commodities combined on which the pesticide is (intended to be) used.
1. Calculation of the National Theoretical Maximum Daily Intake (NTMDI), which uses the MRL as worst residue estimate and national/regional diet statistics to calculate food intake.
The NTMDI is gross overestimate of residue intake, because lifelong exposure to residues at MRL level is very unlikely. Therefore, if the NTMDI is lower than the ADI, consumer risk is highly unlikely and no further dietary risk assessment is needed.
2. If NTMDI is higher than the ADI, the risk assessment is refined by calculating a National Estimated Daily Intake (NEDI). The NEDI calculation uses Supervised Trials Median Residues (STMRs) instead of MRLs, as a more realistic residue estimate. In addition, risk assessment is made more realistic by taking into account factors such as residues in edible portions rather than the whole commodity, effects of food processing and cooking on residue levels, proportion of the crop that is treated. If the NEDI is lower than the ADI, consumer risk is generally considered acceptable.
For acute dietary risks, a single assessment is generally conducted. The acute risk assessment is done for individual crops on which the pesticide is (intended to be) used.
3. Calculation of the National Estimated Short Term Intake (NESTI), which uses the Highest Residue (HR) from supervised trials and combines this with so-called Large Portions (LP) as food intake estimate of the intake of the food item. If the NESTI is lower than the ARfD, the acute dietary risk is considered acceptable.
The dietary risk assessment approach is summarized schematically below.
Spreadsheet calculators are available to assist in the risk assessment calculations.
Interpretation of the outcome
The risk assessment is based on the assumption that the, often internationally established, toxicological reference values ADI and ARfD are also applicable to the national situation. This will generally be the case, because sufficient safety factors are taken into account in setting these reference values.
If national food balance sheets are not available to estimate food intake, GEMS regional cluster diets are generally used instead. These regional diets may be considered representative of the countries that are covered by them. However, in some countries, particular food items which may be consumed in relatively large quantities which are not part of the regional cluster diet. In such a case, the registration authority may wish to adapt the regional diet for these specific food items.
As indicated above, if any of the residue intake estimates is lower than the corresponding toxicological reference value, dietary risks will likely be acceptable.
If, however, the NEDI is higher than the ADI, or the NESTI is higher than the ARfD, consumer risks cannot be excluded. The registration authority may then impose risk mitigation measures, such as reducing the application rate(s) (if possible), increasing the pre-harvest interval(s) (if feasible), or restricting the use of the pesticide to specific crops only. If that still leads to unacceptable consumer risks, the registration authority may consider not to register the pesticide on any food crop.
