(a) Draft Revised Guidelines for Predicting Dietary Intake of Pesticide Residues
(b) Worked Example of Intake Estimate According to the Revised Guidelines
(c) Summary Report of the Joint FAO/WHO Consultation on Food Consumption and Exposure Assessment of Chemicals
(d) Report of Pesticide Residue Intake Studies at International and National Level
23. It was noted that the draft revised Guidelines were before the Committee for comment, but that no action was necessary by the Committee as WHO would publish the Guidelines under the auspices of GEMS/Food. Nonetheless, because the procedures described in the revised Guidelines were being implemented by the JMPR for the purpose of international exposure assessment, the Committee was invited to comment on the risk assessment policies embodied in the Guidelines.
24. There was broad support in principle for the improvement in the estimation of residues by the use of the STMR levels in predicting dietary intake of pesticides. However, some delegations expressed reservations about whether the STMR levels would provide a sufficient margin of safety for consumers and especially for subgroups such as infants, children and farmers. It was explained that for a number of reasons, including actual measurement of residues in food as consumed, the STMR should still be considered an overestimate of residue levels.
25. Some delegations were concerned that the use of the TMDI at the international and national levels in the Guidelines might be misconstrued by some governments and consumers. One delegation raised questions about resource implications needed to implement the Guidelines at the international and national levels, though other delegations were already using the Guidelines. The WHO Representative noted that the Guidelines place emphasis on the use of the best available information, but that further clarification would be provided to communicate the screening function of the TMDI. The TMDI was described as a cost-effective means for focusing resources on pesticides of greatest concern. The presentation of models from complex to simple would help convey the concept that estimating exposure is a continuum of increasing accuracy, but would probably not promote understanding of the underlying principles of dietary exposure assessment.
26. The Observer from the EC stated that the use of average consumption in calculating the National TMDI (NTMDI) was not acceptable and that it was prerogative of countries or a group of countries to choose a model for own assessments. The WHO Representative noted that "average" referred to the national food balance sheet data, known to overestimate food consumption, and which was therefore believed to be protective of sensitive sub-groups. Countries were encouraged to undertake total diet studies to validate their exposure assessment models, and reassure consumers that levels of pesticide residues in food do not exceed established safe limits. This would include using individual food consumption information, where available, in order to protect infants, children and other sub-groups of interest. However, special studies, such as biomonitoring, would be needed for farmers because their exposure patterns are not easily modelled. In response to the concern on the body weight used in exposure assessment at the international level, the WHO representative noted that necessary measures would be taken to reflect different body weights in regions.
27. Consumers International also supported the Guidelines as an improvement in the dietary exposure assessment of pesticide residues, but expressed concerns that overall risk to the consumer from pesticide residues was underestimated, since exposure through drinking water and non-dietary exposures were not given sufficient emphasis, and since a number of issues related to hazard characterization of pesticide residues were not adequately addressed in their view. It was noted that many of the issues raised would be addressed by the JMPR, which included explicit consideration of multimedia exposures.
28. The Committee extended its appreciation to WHO and all that cooperated in the preparation of the revised Guidelines and looked forward to its publication. The Committee requested that WHO take both written and oral comments into consideration in addition to most of the editorial suggestions that the WHO Representative noted would be incorporated. Delegations were invited to provide their comments within the next few months to WHO if they had not already done so. The Committee agreed that the Guideline should be reviewed in the future in the light of experience from operating them and also from further developments in the area of exposure assessment, such as methods for estimating acute hazards in food.
29. Mr. D. Hamilton (Australia) presented the paper and noted that the worked example illustrated practical methodology on best chronic exposure estimations following the recommendations of the Joint FAO/WHO Consultation on Revision of the Guidelines for Predicting Dietary Intake of Pesticide Residues (1995) and the JMPR FAO Panel Workshop (1996) using residue data on parathion-methyl. He stated that using real data required certain decision making, and highlighted the following points:
- Concept of STMR;30. The Committee welcomed the paper as useful guidance and reference material in performing IEDI/NEDI estimations. Some delegations indicated that they had already implemented the recommendations of the above Consultation and Workshop. The Committee noted that the 1996 JMPR had fully endorsed the methodology contained in the paper.
- Different residue definitions for enforcement and dietary intake purposes;
- How to deal with residue trial data which include levels below the limit of determination;
- How to estimate STMRs in various cases;
- Edible portion levels and processing factors; and
- Results of IEDI calculations.
31. The JMPR and governments were encouraged to perform IEDI and NEDI calculations respectively on a routine basis. It was agreed that, if necessary, the Committee might revisit this issue in the future. Noting that the methodology was applicable for chronic exposure assessment, the Committee felt that there would be a need to address a methodology for acute exposure assessment pending the report of the Joint FAO/WHO Consultation on Food Consumption and Exposure Assessment of Chemicals (para. 32).
32. The Joint FAO/WHO Consultation on Food Consumption and Exposure Assessment of Chemicals was held in Geneva from 10-14 February 1997. Mr. C. Warfield (Canada), co-rapporteur of the Consultation, noted that it reviewed and recommended the revision of regional diets used by GEMS/Food for dietary exposure assessments; recommended a procedure for performing acute dietary exposure assessments for adoption by Codex committees; promoted a consistent approach to national and international dietary exposure assessment for all food chemicals and Codex committees; promoted a consistent and transparent approach in conducting dietary exposure assessments, which required good communication between the exposure assessor and the risk manager; and gave special consideration to the needs of developing countries by recognizing the special requirements of such countries.
33. The Committee agreed to discuss the final report of the Consultation at its next Session, with the understanding that a discussion as to the possible elaboration of guidelines for acute dietary exposure assessment could be held at that time.
- Progress Report by WHO on Prediction of Dietary Intake of Pesticide Residues[12]
34. The Representative of WHO presented the referenced papers. The TMDI and, when STMR levels and processing factors were available, the IEDI were evaluated based on the procedures described in the draft Guidelines (CL 1996/33-PR)(paras. 23-31).
35. Calculations were performed for pesticides evaluated by the 1996 JMPR, except for those for which all MRLs had been proposed for withdrawal or no MRLs had been proposed. Of the 23 pesticides considered, 14 had TMDIs and/or IEDIs none of which exceeded the ADI for all regional diets: acephate, aldicarb, bifenthrin, 2,4-D, diazinon, DDT[13], fenarimol, flumethrin, haloxyfop, maleic hydrazide, methamidophos, propoxur, tebufenozide, and teflubenzuron.
36. The TMDI and, in some cases, the IEDI, based on incomplete information, exceeded the ADI for the following, and further information on STMRs and processing factors needed to be reviewed before full IEDIs could be calculated: carbaryl, carbofuran, dimethoate, disulfoton, mevinphos, phorate, thiram and ziram.
37. In the case of thiram and ziram, the prediction of dietary intake was based on an approach which recognizes a common mechanism of toxicity for the dithiocarbamates (105) as a group that included mancozeb, maneb, metiram, propineb, thiram, zineb and ziram. A toxic equivalence correction factor was used to accommodate the different ADIs established by the JMPR for individual dithiocarbamates. In addition, another correction factor was applied to account for differences in molecular weight of the various dithiocarbamates. The Committee agreed, in principle, with the approach, but some delegations requested more time to consider it further. WHO would prepare an improved exposure assessment for dithiocarbamates for the next Session with a more detailed explanation of the procedure and rationale behind the decision steps. (para. 62)
- Report from National Governments[14]
38. The Delegation of the United Kingdom introduced preliminary results of national research into variability of residues. He stated that random occurrence of high level residues had been detected but that even the highest residues were unlikely to lead to adverse health effects. The Delegation invited international cooperation as the problem was likely to be global in scope. He stated that the issue was of concern for registration of pesticides, as opposed to enforcement of MRLs.
39. The Delegation of Australia reported on their national market basket study, conducted for 86 pesticides/contaminants.
