(A) Report of the Joint FAO/WHO Expert Consultation on Food Consumption and Exposure Assessment
(B) Report of Pesticide Residue Intake Studies at International and National Level Based on Revised Guidelines for Predicting Dietary Intake Residues
19. The Committee had before it the Executive Summary[13] of the Joint FAO/WHO Consultation on Food Consumption and Exposure Assessment of Chemicals held in Geneva from 10-14 February 1997. Copies of the final report[14] were also made available at the Session. The WHO Representative recalled that, among other issues, the Consultation had reviewed the general principles for the determination of potential exposure to food additives, contaminants, residues of pesticides and veterinary drugs and certain nutrients and agreed that the principles outlined in the Guidelines for Predicting Dietary Intake of Pesticide Residues (WHO, 1997) were applicable to all food chemicals but that specific procedures might vary.
20. The Consultation had also recommended a procedure for expanding the number of GEMS/Food regional diets to make them more representative of countries in the regions. Following the Consultation, GEMS/Food had developed a proposal for 12 regional diets that would be circulated to Member Governments for comment in the near future. In regard to acute hazard exposure assessment, the Consultation concurred with the York consultation[15] that the MRL or other appropriate high level for the residue be combined with a large portion weight. Exposure for each commodity should be compared to the acute RfD. However, the Consultation also acknowledged that for many commodities residues levels in individual units might exceed the MRL and proposed an approach which makes use of existing data on composite samples to estimate an appropriate high level.
21. The Delegation of the United Kingdom informed the Committee that further studies had confirmed that high unit-to-unit variability was a fairly widespread phenomenon and had been found in a variety of produce, from a variety of sources treated with a variety of pesticides. While the levels did not represent a public health hazard, in some cases the safety margins for consumers might be eroded. The United Kingdom would continue its research to investigate residues in individuals units and a report should be available in early 1999. The United Kingdom intended to host an international workshop on this subject in November 1998. The Chairperson also announced that the Netherlands Government intended to host a one-day symposium immediately prior to the next Session of the Committee to promote a better understanding of the problems of acute hazards and means for assessing and managing risks they pose.
22. In regard to large portion weight, the Consultation recommended that the 97.5 percentile daily consumption for individual food commodities for the general population as well as infants and children ages 6 and under be used for acute hazard exposure assessment. Food consumption should be expressed on a gram per kg body weight basis. As recommended by the 1997 JMPR, the Committee agreed that information on large portion weights would be requested by a Circular Letter from Member countries.
23. The Committee agreed that the report of the Consultation should be on the agendas of the next Sessions of the JMPR and CCPR to consider its recommendations, particularly the procedures for acute hazard exposure assessment.
24. WHO was invited to prepare a guidance document on procedures for estimating an acute reference dose for consideration by the JMPR and the next Session of the Committee.
25. The WHO Representative presented the referenced papers related to exposure assessment. He noted that the revised Guidelines for Predicting Dietary Intake of Pesticide Residues had been published last year, with support of the Netherlands for promotion of the wider dissemination of the methodology, particularly in developing countries.
26. Exposure assessment calculations had been performed for pesticides evaluated by the 1997 JMPR except when no MRLs existed or were proposed, as was the case for amitrole and fipronil, or when no ADI existed, as was the case for guazatine. Of the 23 pesticides, 21 had TMDI and/or IEDI estimates that were below the ADI for the five GEMS/Food regional diets: abamectin, bifenthrin, captan, carbofuran, carbosulfan, chlormequat, chlorothalonil, clethodim, fenbuconazole, folpet, glyphosate (including AMPA[17]), malathion, methamidophos, mevinphos, mycobutanil, phosalone, phosmet, tebuconazole, tebufenozide, thiabendazole and triforine. For two pesticides, fenamiphos and lindane, the TMDI calculations exceeded the ADI in one or more of the regional diets but information was unavailable to calculate a more refined estimate of exposure. The Observer from Consumers International requested that future reports on intake studies be more balanced, to also explain those assumptions that tended to lead to an underestimate of risk, in the interest of solid risk communication.
27. At the last Session, an IEDI calculation for thiram and ziram had been presented based on a common mechanism of toxicity for all dithiocarbamates which used an ADI-adjustment approach. The Committee had agreed, in principle, with the approach but requested WHO to prepare a more detailed explanation for the approach for its 30th Session. Furthermore, the Committee had requested the JMPR to examine the question of common mechanism of toxicity for all dithiocarbamates.
28. In reviewing this issue, the 1997 JMPR had recommended that the risk assessment of dithiocarbamates should be performed for two groups that have two distinct mechanisms of toxicity, namely those that are thyroid toxic (mancozeb, maneb, metiram, probineb and zineb) and those that are not (ferbam, thiram and ziram) and that an ADI adjustment approach be used. Therefore, a revised IEDI calculation for only thiram and ziram (no MRLs are proposed for ferbam) had been performed to assess exposure to these pesticides and the ADI was not exceeded for any of the five GEMS/Food regional diets.
