1 Dr. Len Ritter RISK ASSESSMENT OF RISK ASSESSMENT OF EXPOSURE TO PESTICIDE EXPOSURE TO PESTICIDE RESIDUES IN THE DIETRESIDUES IN THE DIET Executive Directo r Canadian Network of Toxicology Centres and Professor School of Environmental Sciences University of Guelph Guelph, Ontario, Canada Ph. 519-824-4120 x 52980, Fax. 519-837-3861 Email: lritter@uoguelph.ca How do you Estimate Exposure How do you Estimate Exposure Through the Dietary Intake of Through the Dietary Intake of Pesticide Residues ?Pesticide Residues ? The dietary intake of a pesticide residue in a given commodity is generally obtained by performing the following calculation (deterministic): Pesticide residue level (e.g., MRL) X Amount of that commodity consumed How are Pesticide Residue How are Pesticide Residue Levels Estimated ?Levels Estimated ? • The MRL represents the maximum concentration ftiidid( d /k)tht MRL = Maximum Residue Limit o f a pes ti c id e res id ue ( expresse d as mg /k g ) th a t the Codex Alimentarius Commission (CAC) recommends be legally present in food and animal feeds • The MRL is a very conservative estimate of the potential exposure to the pesticide residue as the actual levels found in most foods are well below the corresponding MRLs MRLMRL • In the case where a resulting MRL is at or below the limit of determination/limit of detection (LOD) of the analytical method, the MRL is set at or about the LOD and an asterisk ( * ) is p laced after the MRL in the () p Codex Alimentarius How is Food Consumption How is Food Consumption Estimated ? Estimated ? • The WHO uses data from: - Global Environment Monitoring System (GEMS) – Food Contamination Monitoring and Assessment P P rogram - Five regional diets based on the Food and Agriculture Organization of the United Nations Average daily food consumption values are used in predicting pesticide residue intake for long-term hazards NOT day to day food consumption as there is high variability over a short period of time How do you Estimate the Dietary How do you Estimate the Dietary Intake of Pesticide Residues ?Intake of Pesticide Residues ? TMDI = Theoretical Maximum Daily Intake The TMDI = Σ (MRL x F) Where: MRL = Maximum Residue Limit for a given food commodity F = Regional consumption of that food commodity per person 2 Calculating a TMDICalculating a TMDI The calculation for determining the TMDI may be simple for pesticides with residues in only one food commodity Calculating a TMDICalculating a TMDI This pesticide has only been detected in wheat with a MRL f 0 001 /k Th Example: Pesticide “A” MRL o f 0 . 001 mg /k g. Th e average person consumes approximately 0.2 kg/day of wheat in their diet. Therefore, TMDI = MRL Wheat x Wheat consumption = 0.001 mg/kg x 0.2 kg/day = 0.0002 mg/day Calculating a TMDICalculating a TMDI However, some pesticide residues may be present in many foods, and the calculation may be more complex for pesticides with residues in many food commodities and residues in many food commodities and drinking water ++ Calculating a TMDICalculating a TMDI This p esticide has been detected in wheat , p otatoes Example: Pesticide “B” p,p and eggs, with all commodities having a MRL of 0.001 mg/kg. The average person consumes approximately 0.2 kg/day of wheat, 0.5 kg/day of potatoes and 0.1 kg/day of eggs in their diet. Therefore, TMDI = Σ ( MRL x Food consum p tion ) Calculating a TMDICalculating a TMDI (p) = (MRL Wheat x Wheat consumption) + (MRL Potatoes x Potato consumption) + (MRL Eggs x Egg consumption) = (0.001 mg/kg x 0.2 kg/day) + (0.001 mg/kg x 0.5 kg/day) + (0.001 mg/kg x 0.1 kg/day) = 0.0002 mg/day + 0.0005 mg/day + 0.0001 mg/day = 0.0008 mg/day The IEDI The IEDI –– “The refined TMDI”“The refined TMDI” The International Estimated Daily Intake (IEDI) incorporates correction factors to refine the intake estimate on the basis of all available information, providing a best estimate of dietary intake Factors for refining estimates of residue levels: - Use of median residue levels from supervised trials, instead of the maximum - Consideration of the level of residues found in the edible portion of foods - Effects of processing and cooking on residue levels 3 The IEDI The IEDI –– “The refined TMDI”“The refined TMDI” IEDI = Σ (SMTR x E x P x F) Where: STMR = Supervised trials median residue level for a given food commodity E = Edible portion factor for that food commodity* P = Processing factor for that food commodity F = Regional consumption of that food commodity per person * For some commodities, such as bananas, STMR levels may be determined directly from levels measured in the edible portion Components of the IEDIComponents of the IEDI Median Residue Levels from Supervised Trials (STMRs) - more appropriate starting point for estimating potential exposure potential exposure - uses the most likely residue level (e.g., median level) as opposed to the unrealistic maximum residue level - the STMR value is used by the WHO to calculate the IEDI whenever a STMR has been determined by the Joint FAO/WHO Meeting on Pesticide Residues (JMPR) Components of the IEDIComponents of the IEDI Edible Portion Factor - MRL are established for residues present in the whole commodity, including inedible portions, but for commodities with inedible peel the outer inedible portion of the commodity with inedible peel , the outer inedible portion of the commodity will often contain most of the residue -Residue data, ideally, should quantify the distribution of residue in the whole and the edible portion of a commodity - The WHO has recommended that residue data on the edible portion should be obtained for citrus fruits, bananas, pineapples, kiwifruits, and other fruits with inedible peel; cereals; oilseeds; and cucurbits with inedible peel such as melons Components of the IEDIComponents of the IEDI Processing Factor -Residues on raw commodities are normally dissipated during storage, transport, preparation, commercial processing and cooking - However, in some cases residues may be concentrated in processed fractions, resulting in higher levels than in raw commodities - Data on the effects of storage, processing and cooking on residues are not readily available and requires more work Components of the IEDIComponents of the IEDI Processing Factor - What’s more important to consider with the processing of food is the potential for producing metabolites or degradation products of toxicological concern - MRLs are not usually established for these metabolites or degradation products, but these compounds are of concern in terms human health and should not be ignored Components of the IEDIComponents of the IEDI The Hidden Component – Other Sources of Residues - In estimating dietary intake of pesticide residues, consideration should be given to other known sources of residues other than simply from food commodities Food Sources Drinking Water Sources Residential Sources 4 NTMDI NTMDI –– A National Level A National Level ApproachApproach NTMDI = National Theoretical Maximum Daily Intake The NTMDI = Σ (MRL x F) Where: MRL = Maximum Residue Limit (or National maximum limit) for a given food commodity F = National consumption of that food commodity per person NTMDI versus the TMDINTMDI versus the TMDI Unlike the TMDI, the NTMDI incorporates: - National food consumption data and and - Any available National maximum residue limits (MRLs) derived from supervised trials conducted in the country to determine mean residue levels The NTMDI provides the basis to better characterize the potential for exposure for people living in that country The NEDI The NEDI –– “The Refined IEDI”“The Refined IEDI” The National Estimated Daily Intake (NEDI) like the IEDI, incorporates correction factors to refine the intake estimate on the basis of all available intake estimate on the basis of all available information. However, in this case the NEDI uses the available national data to provide a best estimate of the national dietary intake NEDI = Σ (SMTR x E x P x F) Where: The NEDI The NEDI –– “The Refined IEDI”“The Refined IEDI” STMR = National supervised trials median residue level for a given food commodity E = Edible portion factor for that food commodity* P = Processing factor for that food commodity F = National consumption of that food commodity per person The NEDI The NEDI –– “The Refined IEDI”“The Refined IEDI” There are several factors considered in deriving a NEDI that are not considered in deriving an IEDI Proportion of the crop or commodity treated - Proportion of the crop or commodity treated - Proportions of crop or commodity produced domestically and imported - National monitoring and surveillance data -Total national diet (market basket) studies - Food consumption data, including subgroups of the population Summary of Factors for Refining Summary of Factors for Refining Estimates of Pesticide Residue LevelsEstimates of Pesticide Residue Levels NEDI and IEDI NEDI Only 5 LongLong Term versus ShortTerm versus Short Term Term Exposure EstimatesExposure Estimates Short-term intakes of pesticide residues above an acute RfD are of more concern than a short-term intake above a chronic RfD, because toxicity might be observed after one or only a few exposures - Unlike chronic exposures, which evaluate overall average consumption of a food commodity over a long period of time, acute exposures examine food consumed at a particular meal or over a period of a day. LongLong Term versus ShortTerm versus Short Term Term Exposure EstimatesExposure Estimates Example: - Pesticide “A” has an acute RfD of 0.2 mg/kg bw based on CNS effects and Pesticide “B” has an chronic ADI of 0 . 2 mg/kg bw based on hematological effects 0 . 2 mg/kg bw based on hematological effects - Both Pesticide “A” and Pesticide “B” only have registered uses on rice with the same TMDI value of 0.25mg/kg -It has been found that on average a person consumes one meal every five days that contains rice Is this use safe for acute exposures ? Chronic exposures ? For this example we will consider five days to be a chronic exposure LongLong Term versus ShortTerm versus Short Term Term Exposure EstimatesExposure Estimates 0.25 0.3 “A” Acute RfD 0 0.05 0.1 0.15 0.2 012345 Days TMDI (mg/day) acute chronic “B” chronic ADI LongLong Term versus ShortTerm versus Short Term Term Exposure EstimatesExposure Estimates - In estimating the residue level in a food commodity in an acute exposure assessment, there must be consideration of the variability in the residue level in the food ( e. g . , difference in residue levels between two (g, carrots) - To address this variability, unlike in a chronic exposure assessment, the use of median residue levels is not appropriate and results at the high end of the residue distribution should be used in an acute exposure assessment LongLong Term versus ShortTerm versus Short Term Term Exposure EstimatesExposure Estimates - The need to consider the consumption of a number of food commodities to determine the total exposure to a particular pesticide residue is not generally relevant in an acute ex p osure situation p - It is considered unlikely that an individual will consume two different food commodities in large quantities within a short period of time and that those food commodities will contain the same pesticide at its MRL LongLong Term versus ShortTerm versus Short Term Term Exposure EstimatesExposure Estimates - Therefore, the calculation of an acute exposure can generally be based on the consumption of a large portion of a single commodity H h hi h id lik l t b f d i - H owever, w h en hi g h res id ues are lik e l y t o b e f oun d i n more than one commodity it may be necessary to estimate the total intake - In such cases, it is still inappropriate to sum the intake derived from the intake of the individual commodities and more sophisticated models that can incorporate the probability of selecting foods with different residue levels should be used 6 Thank YouThank You . 1 Dr. Len Ritter RISK ASSESSMENT OF RISK ASSESSMENT OF EXPOSURE TO PESTICIDE EXPOSURE TO PESTICIDE RESIDUES IN THE DIETRESIDUES IN THE DIET Executive Directo r Canadian Network. lritter@uoguelph.ca How do you Estimate Exposure How do you Estimate Exposure Through the Dietary Intake of Through the Dietary Intake of Pesticide Residues ?Pesticide Residues ? The dietary intake of a pesticide. for acute exposures ? Chronic exposures ? For this example we will consider five days to be a chronic exposure LongLong Term versus ShortTerm versus Short Term Term Exposure EstimatesExposure