6
Pesticide Residues

DATA ON DIETARY LEVELS of pesticide residues combined with food consumption estimates provide the basis for exposure estimates used by the Environmental Protection Agency (EPA) to assess the risks of pesticide exposure in the diet. Thus, sampling and residue testing methods to estimate levels of pesticide residues in the food supply are extremely important components of the risk assessment process.

The committee examined pesticide usage, residue sampling and testing methods, and the data pesticide residues to

  • understand the relative quality of data sets available to EPA as a foundation for recommending practical improvements in data collection and testing;

  • identify the foods in the diets of infants and children with residues of pesticides that cause the greatest public-health concern;

  • assess the need for residue sampling methods and residue testing procedures that can provide the data needed to ensure the protection of infants and children;

  • recommend residue monitoring methods that could be incorporated into an exposure assessment methodology that would ensure the protection of infants and children;

  • identify steps to improve risk assessment and establish priorities for those steps; and

  • determine which, if any, data are sufficient quality to support risk assessment models designed to protect infants and children.

SOURCES OF DATA ON USAGE

Despite the importance pesticides have attained in agricultural production, data on the amount and distribution of their use are remarkably



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Pesticides in the Diets of Infants and Children 6 Pesticide Residues DATA ON DIETARY LEVELS of pesticide residues combined with food consumption estimates provide the basis for exposure estimates used by the Environmental Protection Agency (EPA) to assess the risks of pesticide exposure in the diet. Thus, sampling and residue testing methods to estimate levels of pesticide residues in the food supply are extremely important components of the risk assessment process. The committee examined pesticide usage, residue sampling and testing methods, and the data pesticide residues to understand the relative quality of data sets available to EPA as a foundation for recommending practical improvements in data collection and testing; identify the foods in the diets of infants and children with residues of pesticides that cause the greatest public-health concern; assess the need for residue sampling methods and residue testing procedures that can provide the data needed to ensure the protection of infants and children; recommend residue monitoring methods that could be incorporated into an exposure assessment methodology that would ensure the protection of infants and children; identify steps to improve risk assessment and establish priorities for those steps; and determine which, if any, data are sufficient quality to support risk assessment models designed to protect infants and children. SOURCES OF DATA ON USAGE Despite the importance pesticides have attained in agricultural production, data on the amount and distribution of their use are remarkably

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Pesticides in the Diets of Infants and Children scanty. There is no single, comprehensive data source, derived from actual sampling, on pesticide usage for all crops and all chemicals. The U.S. Department of Agriculture's (USDA) Economic Research Service (ERS) conducted national surveys of pesticide use in 1964, 1966, 1971, 1976, and 1982; smaller areas and fewer crops have been included in successive surveys. The 1964, 1966, and 1971 surveys included field crops, fruits, vegetables, and livestock. In 1976 fruits and vegetables were excluded from the survey, and in 1982, only major field crops (e.g., corn, soybeans, cotton, wheat, barley, oats, peanuts, tobacco, alfalfa, and hay) were sampled (Osteen and Szmedra, 1989). The foci of later reports on pesticide usage are even narrower: vegetable, melon, and strawberry crops in Arizona, Florida, Michigan, and Texas (USDA, 1991); fruits and nuts, in 12 states (USDA, 1992a); and eight field crops (corn, cotton, peanuts, potatoes, rice, sorghum, soybeans, and wheat) in different numbers of states, ranging from 47 states for corn down to 2 states for rice and 1 for durham wheat (Osteen and Szmedra, 1989). Resources for the Future maintains a county-based file of annual pesticide usage estimates by county and by crop for the 184 widely used pesticides that appear on EPA's list for the National Ground Water Survey and the California Priority Pollutant List (Gianessi, 1986). The usage information was derived from the limited ERS surveys and from the annual California survey (State of California, 1981), which included only restricted-use of chemicals until 1991, when the state's reporting system was extended to all pesticides, including unrestricted chemicals. Resources for the Future has also estimated the amounts of pesticides applied to lawns and in nurseries. The data in Table 6-1 illustrate the variation in the kind and amount of pesticides used on crops in various geographic regions. The corn belt, for example, accounted for 39% of all pesticides used on major crops in 1982. Most of this volume was represented by herbicides; fungicides constituted only 2% of total usage. In contrast, the southeast accounted for only 8% of total pesticide applications but for 66% of fungicides used. There are similar differences in use patterns between other regions. The implications for residue and exposure estimation are more clearly illustrated in Table 6-2, which focuses on one crop (fall potatoes) and one class of pesticides (fungicides) and their application in the northeast, midwest, and western regions of the United States. In 1991, 96% and 90% of croplands planted with potatoes in the northeast and midwest, respectively, were treated with fungicides, while only 52% of croplands in the west were treated. Fungicides were also applied more times during the growing season in the northeast and midwest. As a result, the northeast, which accounts for 11% of the hectares planted with potatoes, accounts for 30% of all fungicide hectare treatments

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Pesticides in the Diets of Infants and Children TABLE 6-1 Regional Distribution of Pesticide Use on Major Crops in Selected Regions in 1982   Amounts of Active Ingredient Used (1,000 lbs.) and (Percent) of Total, by Geographic Region     Total Usage Pesticide Northeast Lake Corn Belt No. Plains Appalachia Southeast Delta So. Plains Mountains lbs. (1,000) % Herbicides 14,727 (3) 62,778(14) 197,894 (43) 53,107 (12) 34,142 (7) 22,884 (5) 41,168 (9) 17,554 (4) 11,315 (2) 455,569 99a Insecticides 1,915 (3) 3,800 (5) 17,307 (24) 7,784 (11) 5,833 (8) 13,460 (19) 11,567 (16) 7,149 (10) 2,418 (3) 71,233 99a Fungicides <10 (<1) 80 (1) 147 (2) 38 (1) 849 (13) 4,331 (66) 923 (14) 213 (3) 12 (2) 6,593 102a Other <10 (<1) <10 (<1) 72 (<1) 130 (1) 11,540 (47) 2,533 (10) 4,863 (20) 2,422 (12) 2,247 (9) 29,307 102a Total 16,642 (3) 66,658 (12) 215,420 (39) 61,059 (11) 52,364 (9) 43,208 (8) 58,521 (10) 27,838 (5) 15,992 (3) 557,702 100 NOTE: Major crops included corn, soybeans, cotton, wheat, barley, oats, peanuts, tobacco, alfalfa, and hay. a Totals do not add up to 100 due to rounding. SOURCE: Based on data from Osteen and Szmedra, 1989.

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Pesticides in the Diets of Infants and Children TABLE 6-2 Total Fungicide Use on Fall Potatoes in the United States, 1991   Production   Hectares Treated     Regiona Planted (1,000 ha) % of Total Planted Hectares No. (1,000 ha) % in Region Average No. of Applications % of Total Hectare Treatmentsb Northeast 51 11 49 96 5 30 Midwest 133 29 119 90 4 42 West 269 59 141 52 2 28 Total 453 99 309   4 100 NOTE: Numbers do not add up to 100 due to rounding. a Northeast: Maine, New York, Pennsylvania; Midwest: Michigan, Minnesota, North Dakota, Wisconsin; West: Colorado, Idaho, Oregon, Washington. b Hectare treatment: number of hectares treated times number of applications per year. SOURCE: Derived from USDA, 1992c. In contrast, the west, which accounts for 59% of all hectares planted with potatoes, accounts for only 28% of total fungicide hectare treatments. This variation of pesticides used on the same crop grown in different regions means that the amount and kind of residues will depend not only on the crop, but also on where it is grown. THE OCCURRENCE AND FATE OF PESTICIDE RESIDUES Pesticide residues originate when a crop or food animal (commodity) is treated with a chemical or exposed unintentionally by drift, in irrigation water, in feed, or by other routes.  The size of the residue depends on the exposure level (treatment rate), its dissipation rate, environmental factors, and its physical and chemical properties.  For example, an insecticide sprayed on apples any volatilize into the atmosphere.  This is influenced by the insecticide's volatility or vapor pressure and the temperature and wind movement in the orchard. Removal by rainfall or overhead irrigation is governed by the insecticide's water solubility and the amount of rain or irrigation water. The chemical may also degrade (as influenced by the molecular makeup of the insecticide  and by such factors as sunlight, moisture, and temperature) or it may dissipate by growth dilution (e.g., as the fruit becomes larger, the residue concentration will decrease even in the absence of physical or chemical dissipation).  In farm animals and some plants, metabolism and excretion are the primary mechanisms. The

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Pesticides in the Diets of Infants and Children degradation products become the major constituents of the remaining residue. In a few cases, chemical residue concentrations may actually increase over time after exposure ceases. This would result from weight loss by the commodity, e.g., loss resulting from the conversion of grapes to raisins after treatment with a relatively stable, nonvolatile chemical. The overall dissipation rate is a composite of the rate constants of the individual processes (e.g., volatilization and degradation). Typically, overall residue concentrations (parent plus degradation products) decrease over time after exposure ends. Because most individual dissipation processes follow first-order kinetics, overall dissipation will have the characteristics of first-order kinetics. In first-order decline, the logarithm of concentration is linearly related to time, and a plot of concentration remaining versus time is asymptotic with respect to the time coordinate. Thus, residue concentrations will approach zero over time but in theory will never cease to exist entirely (Zweig, 1970). Stated simply, a commodity treated with or exposed to a pesticide theoretically can never totally be rid of all traces of residue. In time, however, the residue will cease to be detectable because of the limitations of current measuring instrumentation and the continuing asymptotic decline processes. This limit of detection (LOD) will therefore vary according to the sensitivity of the analytical method used. (LODs are described below under ''Detection Limits.") Conventionally, residues in raw commodities are monitored until they have declined to a concentration approximately 1/10th that of the legal maximum—that is, the tolerance or action level. Very little public monitoring is intended to identify the residues that the consumer may ingest, which may range from the legal maximum to 1/10th, 1/100th, 1/1,000th, or smaller fractions of that level on foods prepared for consumption. One can expect that consumers are exposed to small residues if their food was treated with or exposed to pesticides during production, processing, or preparation; however, we do not always know the quantity of those residues either because they are lower than the LOD or because there are no monitoring data available. For these reasons, it is difficult to estimate actual dietary exposure to pesticides and any associated risk with a high degree of certainty. PESTICIDE REGISTRATION AND THE DEVELOPMENT OF ANALYTICAL METHODS Early in the development of a pesticide, the manufacturer must identify the analytical methods used to ascertain the concentrations of chemicals in formulations (formulation methods) and the fate of the material on target crops, in laboratory animals and livestock, and in environmental media (soil, water, air) that might be exposed to the chemical (residue

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Pesticides in the Diets of Infants and Children methods). Most companies that develop and register chemicals employ staffs to develop these analytical methods, whereas others hire or fund commercial or university laboratories for this purpose. Development of analytical methods is a lengthy and technically difficult process because the methods must account for the parent chemical or control agent as well as toxicologically significant formulation impurities, metabolites, and environmental conversion products. The impurities and products may not be known early in the development phase and thus must be included later but before registration is sought from EPA. Before a pesticide can be registered under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), a tolerance level must be established for each food use or an exemption granted, e.g., for a pesticide that is essentially nontoxic. To obtain a formal tolerance level, pesticide manufacturers must submit their analytical methods to EPA, which then verifies that the pesticide can be detected at a certain tolerance level for each proposed food use. It is not unusual for a food tolerance level to include the parent chemical and several breakdown products. In such cases, versatile residue detection methods must be available to detect the various tolerance levels in every food or feed product for which registration is being sought. Typically, the primary method will have several variations extending it to soil, water, air, and nontarget organisms such as fish and wildlife. The manufacturer applies these methods to determine the rate of dissipation or decline of the pesticide on target crops in field trials. The results are submitted to EPA with the registration data for use in establishing a tolerance level for the raw agricultural commodity and determining the interval required between the last application of the pesticide and harvest to achieve residues below that tolerance. Field trials are conducted in several geographical regions of the United States that typify areas in which the crop is produced, so that different climatic conditions and soil types are represented. The test plots are treated with pesticides in concentrations high enough to eradicate a large percentage of the target pest(s). If the trials are not complete, if the data are too variable, if conversion products are not adequately included, or if the analytical methods themselves are considered imprecise, inaccurate, not sufficiently sensitive, or otherwise deficient, registration may be denied. EPA may base its judgment on the data submitted by the manufacturer, or it may inspect the company's raw data in accordance with the FIFRA provision for data audits. Field trial data are further evaluated in Chapter 7. Methods must be provided by the manufacturer when requested by any federal or state regulatory agency and may be included in the Pesticide Analytical Manual, Volume II (PAM II): Methods for Individual Residues,

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Pesticides in the Diets of Infants and Children which was first published by the Food and Drug Administration (FDA) in 1968 but has been updated in a series of revisions since then. These methods do not need to fit within the available multiresidue methods (MRMs) used by the FDA to screen food or feed products entering commerce (see section on "Methods for Sampling and Analysis," below, for a further discussion of MRMs). More recently, EPA has asked pesticide manufacturers to determine whether new compounds are detectable by existing MRMs. If they are not, however, the registration process is not impeded. Interregional Project Number 4 Use of pesticides on some crops (e.g., strawberries, hops, artichokes, cranberries) may be too limited to provide the economic incentive needed for chemical companies to develop the analytical methods and residue data required for registration. In such cases, this work is performed by Interregional Project Number 4 (IR-4), which operates within State Agricultural Experiment Stations (SAES) with funding from USDA's Cooperative State Research Service (CSRS) and Agricultural Research Service (ARS). The nation's four IR-4 leader laboratories are located at Cornell University, the University of Florida, the University of California at Davis, and Michigan State University. Several participating laboratories are situated at other land-grand institutions and within ARS. The IR-4 laboratories use methods provided by manufacturers to EPA for pesticide residues on the major crops listed on the chemical's label. If the method fails on the minor crop, they modify the company method to make it fit the minor crop situation. Occasionally, they develop new methods for minor crops of interest. SAES or ARS field scientists establish the plots, sample the commodity at harvest, and provide samples to IR-4 laboratories, which then conduct the analyses. All data are submitted to EPA. If the petition is approved, the minor crop is added to the pesticide label. IR-4 actions annually account for approximately half of the petitions processed by EPA. Universities and the ARS Several U.S. universities and the ARS conduct research on pesticides to study their field behavior, formation of breakdown products, persistence during food processing and storage, and analytical behavior, Many advances in food residue chemistry (e.g., detection of previously unrecognized toxic metabolites) and new approaches to residue analysis (e.g., the immunoassay) result from this basic research. In addition, this academic

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Pesticides in the Diets of Infants and Children environment provides the training ground for pesticide scientists who eventually enter the industrial, government, and commercial sectors. METHODS FOR SAMPLING AND ANALYSIS Sampling Sampling should be conducted  by persons trained in the practice of sampling;  randomly, so that all individuals in the population sampled have an equal chance of selection in the final analysis; with replication, so that analytical results can be treated statistically;  in such a manner as to maintain sample integrity by adequate containment, preservation, and prevention of contamination; and  with care and attention to record keeping, including visual observations, sample preservation, and safeguards against cross-contamination. Usually omitted from reports are the manner of collecting samples (where, by whom, and how) and information on compositing, subsampling, preservation of samples and subsamples, and other important matters. Lykken (1963) generalizes, however, that all residue monitoring programs operate somewhat as follows:  Several commodity units (e.g., bunches of grapes, oranges, heads of cabbage) are taken from the field or lot to be sampled.  These commodity units are composited to form to gross sample.  The gross sample is reduced in size to produce the composite sample.  The composite units are then peeled, husked, or further reduced in size by cutting or chopping in accordance with the Code of Federal Regulations, which identifies the portion(s) of the commodity to which the tolerance applies.  The individual parts of the commodity may then be quartered to reduce bulk and perhaps subdivided to smaller aliquots. These samples are generally frozen or preserved in some other way, transported to the laboratory, and preserved further until analyzed. If a freezer stability test is to be conducted (a recent Good Laboratory Practice [GLP] requirement; 40 CFR Part 160), control samples may be spiked at this point and then handled the same as the treated sample. This is usually done when field plots are sampled to determine residues for registration requirements, but less frequently for monitoring and enforcement of tolerance levels for registered chemicals. Sampling and sample handling for field trials are described by the National Agricultural Chemicals Association (NACA, 1988).

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Pesticides in the Diets of Infants and Children  At the time of analysis, individual subsamples may be more extensively chopped or blended or reduced further in size prior to extraction with a solvent and analysis.(See PAM I or II for more detailed description.) The absence of uniform training has likely led to haphazard sampling or bias resulting in samples that are neither random nor representative. To rectify this situation, FDA and most state agencies are taking steps to improve their training and written sampling guidelines. Furthermore, true replication, with three or more field composites, appears not to have been common practice, evidenced by the fact that averages and standard deviations are absent from virtually all residue monitoring reports. Sample handling has improved since implementation of GLP protocols; but again, without accompanying quality assurance records, older data must be questioned for reliability. EPA and FDA are now training and certifying field inspectors to ensure proper sampling by all personnel engaged in work to meet FIFRA requirements. In addition, the American Chemical Society's Committee on Environmental Improvement has prepared a comprehensive volume dealing with the basics of environmental sampling (Keith, 1988). Analysis Methods for analyzing pesticides are expensive, time consuming, and difficult, and they require a skilled analyst. Furthermore, methods are tailored to specific purposes (e.g., monitoring, enforcement, or registration). As a result, considerable variability is associated with the methodology. In many cases, descriptions of differences among the specific methods used do not accompany the residue data, thus diminishing public confidence in the data. Furthermore, the committee found no analytical program directed toward water specifically as an ingredient of foods or as a component added to foods. This results in an important gap in the residue data, since water represents such a large part of the diets of infants and children. There are two general types of analytical methods for determining residues in foods: single residue methods and multiresidue methods. These are described in the following sections. Single Residue Methods Single residue methods (SRMs) are used for the quantitative determination of a single pesticide (and its toxicologically important conversion products, e.g., through metabolism or degradation) in all foods for which tolerance levels have been established. This is generally the type of method

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Pesticides in the Diets of Infants and Children submitted by the manufacturer to EPA and eventually published in PAM II after registration is secured. It may also be the method used (sometimes in modified form) for IR-4 petitions. Multiresidue Methods Multiresidue Methods (MRMs) are capable of detecting and quantifying more than one pesticide in more than  one food. These methods are commonly used by government agencies for surveillance and monitoring to determine which pesticides (and how much) are present in a given food sample. FDA's MRMs are published in PAM I; the MRMs of state agencies, foreign governments, private industry, and academia are published in the open literature or in special reports. Some MRMs are rapid; others are more comprehensive and therefore more time consuming. In general, MRMs may be used for screening and quantitation. In screening, MRMs are used to determine rapidly if any  pesticide is present near or above the tolerance level. This approach usually precedes a more detailed analysis. Cholinesterase enzyme inhibition tests screen for organophosphorus and carbamate insecticides; insect bioassays screen for any insecticide residue. Immunoassays may be used in the future for targeted chemicals or classes of chemicals. In quantitation, MRMs are used to detect and measure multiple pesticide residues and their metabolites that might be present in a given sample. These MRMs are usually based on gas or liquid chromatography or both. FDA and other agencies often use simplified versions of MRMs in their surveillance program to determine if violations exist in given samples before proceeding to full quantitation with a more elaborate  version. Because all MRMs can accommodate only a limited number of chemicals, agencies use SRMs for targeted pesticides that are not included in the MRM. They also use SRMs in special circumstances such as when public health is endangered by a single pesticide or when a single pesticide comes under special review and, thus, special scrutiny is required for its presence in foods. Most laboratories improvise when using an MRM, and the improvisations are often not subject to peer review or published. Requesting the latest method from an agency is usually the only way to obtain up-to-date information on the method being used, the number of pesticides it can accommodate, and its LOD. MRMs used by regulatory laboratories are frequently modified in response to changing availability of solvents and analytical instrumentation within the laboratory and the need to expand the MRM's coverage or lower its detection limit.

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Pesticides in the Diets of Infants and Children Criteria for Selecting a Method Single Residue Methods or Multiresidue Methods? SRMs are selected when the sample is known or believed to contain the residue of a chemical not included in the MRM. MRMs are used when the residue history of the sample is unknown and the presence and quantity of pesticide residues must be determined. MRMs will provide information on a much broader range of pesticides than an SRM for the same investment of time, energy, and resources. Breadth of Applicability MRMs most commonly used by the FDA can determine roughly 50% of the approximately 300 pesticides with EPA tolerances and other chemicals for which no tolerances have been established. Some of the MRMs can also detect many metabolites, impurities, and alteration products of pesticides with and without tolerances (FDA, 1991). Typically not included are polar chemicals of high water solubility (e.g., paraquat, glyphosate), very volatile chemicals (e.g., fumigants), and compounds that are unstable to Florisil chromatography (e.g., some carbamates). An aliquot of the sample (or its extract) must be analyzed separately so that these chemicals can be included in the analytical report. Detection Limits All analytical methods have a limit below which the chemical could not be detected even if present. This limit of detection (LOD) is the lowest concentration that can be determined to be statistically different from a blank. Elsewhere in this report, the committee refers to the limit of quantification (LOQ), which differs from the LOD in that it refers to the concentration above which quantitative results may be obtained with a specified degree of confidence. The LOD is influenced by extraneous, background material that is always present in the sample and the sensitivity of the instrumentation used for detection and quantification. Moreover, the LOD may vary according to application. LODs are determined by analyzing background (untreated) samples of the food products of interest and spiked samples, which contain known amounts of the chemicals. LODs for a given method will vary with the type of sample, the chemical, and the extent of sample cleanup provided. LODs can be as low as twice the background reading. That is, a signal

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Pesticides in the Diets of Infants and Children TABLE 6-9 Six Foods Among the 18 Most Consumed by Infants and the Tolerances and Residue Levels of Six Pesticides Detected in Them     Residue Level, ppm Food Pesticide Mean Detected Maximum Detected EPA Tolerance Apples, fresh Ethylenebisdithiocarbamate       (EBDC) 0.0937 0.7700 7.0 Benomyl 0.1635 2.6400 7.0 Captan 0.0352 3.4000 25.0 Chlorpyrifos 0.0064 0.9000 1.5 Dimethoate 0.0006 0.1900 2.0 Parathion-methyl 0.00176 0.2600 1.0 Peaches, fresh EBDC 0.0154 0.2000 10.0 Benomyl 0.2095 1.1100 15.0 Captan 0.1329 9.6900 50.0 Chlorpyrifos 0.0013 0.1300 0.05 Dimethoate 0.0001 0.0875 NT Parathion-methyl 0.0024 0.0900 1.0 Pears, fresh EBDC 0 0 7.0 Benomyl 0.0691 1.5900 7.0 Captan 0.0155 1.0000 25.0 Chlorpyrifos 0.0003 0.0400 0.05 Dimethoate 0.0024 0.3850 2.0 Parathion-methyl 0 0 1.0 Carrots EBDC 0 0 7.0 Benomyl 0 0 0.2 Captan 0.0021 0.8300 2.0 Chlorpyrifos 0.0001 0.0200 NT Dimethoate 0 0 NT Parathion-methyl 0 0.0100 1.0 Peas, succulent, garden EBDC 2.5964 23.0000 7.0 Benomyl 0.1000 0.4100 NT Captan 0 0 2.0 Chlorpyrifos 0.0017 0.4800 NT Dimethoate 0.0341 2.8775 2 Parathion-methyl 0.0009 0.5500 1.0 Beans, succulent, green EBDC 0.1042 2.0000 10.0 Benomyl 0 0 2.0 Captan 0.0028 1.0000 NT Chlorpyrifos 0.0027 0.5650 0.05 Dimethoate 0.0120 2.3450 2.0 Parathion-methyl 0.0001 0.7000 1.0 NOTE: NT, no tolerance level has been established by EPA. SOURCE: Based on FDA Surveillance Data, 1988–1989, unpublished.

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Pesticides in the Diets of Infants and Children on pesticide residues in food must be considered in a critical evaluation of the dietary exposure of infants and children to pesticides. Earlier in this chapter, the committee discussed the effects of processing on pesticide residues on the ingredients used in infant formula. Elkins (1989) reported NFPA data on the effects of food processing operations on the residues of pesticides permitted on raw agricultural commodities. In most instances, washing by itself was shown to reduce residues, blanching reduced them even further, and the canning process led to even further decreases. These data indicated that in tomatoes and green beans subjected to each of these three steps, levels of malathion were reduced 99%  and 94%, respectively, and carbaryl concentrations decreased 99% and 73%. Levels of parathion were reduced 66% in spinach and 10% in frozen broccoli. Elkins also pointed out that some processing activities can actually increase levels in certain instances. For example, levels of ETU were increased 94.5% in frozen turnip greens as a result of maneb degradation during cooking in a saucepan. Elkins noted that the distribution of different pesticides in a product is also an important consideration. In tomatoes, for example, malathion tends to concentrate in the peel or waste, while carbaryl, a fairly polar compound, is easily removed by washing and does not tend to concentrate in waste material. Table 6-10 lists the residues of both pesticides in the washed and unwashed product, in the peeled tomato, and in waste material. The committee reviewed unpublished data provided by the NFPA on pesticide residues found in foods used in processed baby foods. These foods, along with infant formula, comprise a large proportion of the infant's diet. Of the 6,580 samples tested in 1987, NFPA members found residues in 165 samples (2.5%) distributed among a total of 7 foods (Table TABLE 6-10 Pesticide Concentrations in Washed and Unwashed Tomatoes, in Peeled Tomatoes, and in Waste Material Tomato Product Malathion, ppm Carbaryl, ppm Unwashed 15.9 5.2 Washed 0.8 0.14 Peeled 0.1 Trace Waste 5.3 0.1   SOURCE: Elkins, 1989. Reprinted from Journal of the AOAC, Volume 72, Number 3, pages 533–535, 1989. Copyright 1989 by AOAC International.

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Pesticides in the Diets of Infants and Children TABLE 6-11 Number of Samples and Detections for Foods Used in Baby Food Product Sample Size No. of Ratio of Samples with Detected Residues Ratio of Maximum Detection to LOQ Apples, fresh 1,560 27 11 Apples, juice 1,602 24 5.6 Apricots, fresh 260 0 — Bananas, fresh 472 39 4.1 Beans, succulent, green 28 0 — Carrots 183 0 — Corn, sweet 2 0 — Grapes, juice 3 0 — Oats 36 0 — Orange, juice 220 0 — Peaches, fresh 356 21 13.6 Pears, fresh 328 47 140 Peas (garden), green immature 1 0 — Pineapples, fresh, juice 1 0 — Plums-Prunes, dried 78 0 — Plums (Damsons), fresh 193 0 — Rice, milled 42 0 — Squash, summer 226 0 — Squash, winter 174 2 3.2 Sweet potatoes (including yams) 815 5 4.2   SOURCE: National Food Processors Association, 1987, data unpublished. 6-11). As shown in the table, the largest number of positive samples and the highest ratio of detected residue to the LOQ were noted for fresh pears. The ratio represents a comparison of the highest concentration of amitraz found in pears to the relatively low (1 ppb) LOQ. The highest concentration found—140 ppb—is considerably lower than the EPA tolerance of 3,000 ppb. A comprehensive study of the effects of processing on food residues is badly needed. This study should be undertaken by EPA, FDA, or USDA working through grants and contracts to university and private laboratories. The committee believes that the information presently available needs to be brought together in a review document and then supplemented with additional studies. However, this requirement is beyond the time and resources available to the committee. The committee therefore opted to provide some brief examples of the type of information that can be obtained on many of the foods consumed by infants and young children.

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Pesticides in the Diets of Infants and Children In these examples, the committee applies basic and deliberately simplified explanations of several processes involved in food preparation and processing. In addition to infant formulas, which have already been discussed, the most critical and highly consumed foods are apple-based processed products and cereal-based foods. Following are brief overviews of the processing factors that influence pesticide residues in these foods. Apple-Based Foods Apple-based foods constitute a substantial portion of foods consumed by infants and young children, as shown in Chapter 5. Knowledge of the form in which these products are consumed is important to the understanding of residue data. Virtually all the foods consumed by infants are processed, and most are manufactured by a limited number of processors, who exercise stringent controls. The processing of apples for applesauce (which forms the basis for many foods) and apple juice is specific, and the controls for the finished products are extensive. Steps in processing of apples for use in foods for infants and children involve washing, blanching, peeling, pressing (for juice), finishing (removal of fibrous or indigestible material), and heating (sterilization). The washing process removes the exterior (nonsystemic) compounds, and is effective in the removal of many pesticides. Blanching is done with steam or hot water, primarily to inactivate enzyme systems and to prevent discoloration. It involves treatment at high temperature for a relatively short time. The skin is removed by abrasion or by peeling with a knife. A substantial portion of nonsystemic pesticides is concentrated at the surface of the apple or in the peel. The calix (or core) is removed by actually cutting or by removing seeds and fibrous material with a finisher. Physical pressure, usually accompanied by heat or enzyme treatment, is used to separate clear juice from cellulose, fibrous (pectin), and protein material to yield a clear, light-colored juice. Pressing is conducted through a filter press with paper filtration or by ultrafiltration. Substantial pesticide concentrations are removed with the fibrous or protein fractions of apple solids. Thus, estimates at the farm gate are not reflective of the residue content of foods that have undergone such processing steps. Infant Cereal Infant cereal is consumed by a large percentage of infants. The lack of large pesticide residues detected in these products probably reflects the extensive and unique processes to which they are subjected. The basic ingredient of infant cereal is flour, which is the dehulled and

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Pesticides in the Diets of Infants and Children fractionated grain (rice, oat, or barley) that has been milled. The flour is formed into a slurry, treated with a hydrolyzing enzyme (a-glucosidase), then heated to cook the cereal, destroy enzyme activity, and sterilize the food. The slurry is then dried on a steam-heated drum, which effectively distills off into steam any volatile material subject to partition. The resulting product is a sterile, precooked, partially hydrolyzed cereal-based food. Clinical trials of usage have established the acceptance and digestibility of cereal for infant consumption. There has been no relationship established between retention of components in original grain to finished, processed infant cereal. CONCLUSIONS AND RECOMMENDATIONS Data on residues on foods are collected by FDA, state agencies, the food industry, private organizations, and in university programs such as IR-4. Other government, industry, and academic sources were identified by the committee for specific categories such as water, infant formula, and human milk, which are particularly important in the diets of infants and children. The committee also reviewed the complex and varied methods for pesticide residue analysis and sampling performed by these groups. Conclusions There is no comprehensive data source, derived from actual sampling, on pesticide residue levels in the major foods consumed by infants and children. For example, of the foods (expressed as commodities) most consumed by nursing and nonnursing infants under 1 year of age, data showing the 18 foods most frequently tested for pesticide residues in the FDA Surveillance Program (Table 6-6) include only 4 of the 18 major foods consumed by this age group. Data on pesticide residues in foods are extensive, but are difficult to interpret because of variation in sample selection, analytical methods, and quality control procedures. The extensive data available from numerous testing programs for pesticide residues in food would be far more useful in profiling residues in the diet if they were presented in a more complete and coherent form. Food samples analyzed for pesticide residues may have been selected for surveillance, compliance, or other purposes. Analytical methods, their limits of quantification, and their degrees of precision and accuracy may therefore differ among laboratories. Record-keeping practices in pesticide

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Pesticides in the Diets of Infants and Children residue monitoring programs are generally not uniform and not well articulated. Many of the existing data on pesticide residues were generated for targeted compliance purposes. Although these data may be appropriate for enforcement, they have limited usefulness in generation- or population-based evaluations of actual exposure. For example, the sampling technique over represents suspected violators and does not adequately represent foods eaten in large quantities by infants and children. The limited data available suggest that pesticide residues are generally reduced by processing; however, more research is needed to define the direction and magnitude of the changes for specific pesticide-food combinations. Infant formulas and processed baby foods are routinely monitored to ascertain pesticide residue levels. Although sampling and analytical techniques lack the desirable degree of uniformity, residues were not generally detected in these products. Human milk is a food whose constituents are subject to wide variation, depending on the diet, medical history, and exposure of the mother. For some infants this may represent the primary route of exposure. Ongoing surveillance indicates that pesticide concentrations in human milk continue to decline over time, especially since organochlorine pesticide use in the United States has been reduced. Pesticide residues in water—both drinking water and water used in food preparation—have previously been largely overlooked in assessing dietary exposure of infants and children. Recommendations A computerized data base for pesticide residue data collected by laboratories in the United States should be established. If standardized reporting procedures were developed and adopted, pesticide residue data could be accumulated in a national data bank in a form accessible for future use. In future applications of residue data, consideration should be given to the development of a standardized reporting format for use by all laboratories involved in residue analyses. Since pesticide residue data are

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Pesticides in the Diets of Infants and Children collected by a variety of laboratories using different methods for sampling and analyses, it would be desirable to maintain records of sample collection, analytical methods used, the basis of detection, and the precision and accuracy of the results obtained. Reports of pesticide residue testing should indicate food commodity analyzed (and whether it is processed or unprocessed), Ranalytical method used, compounds tested including metabolites), quality assurance-quality control (QA-QC) notation, and limit of quantification (LOQ). These reports should follow a standard format, should be timely and consistent, and should include not only the LOQ but also all negative and positive findings. The methods of reporting must also be consistent (e.g., using similar computer software). Food residue monitoring programs should target a special market basket survey designed around the diet of infants and children. The methods to be used in this survey should be validated using fortified samples circulated among the participating laboratories. Residue analysis methods need to be standardized in a timely manner through an independent review and validation process conducted by a government or professional organization. FDA, working with USDA, EPA, and state and other federal agencies, needs to create: a clearly explained sampling strategy that could be used to ascertain the representativeness of the results of food residue analyses; guidelines for those generating, processing, and using residue data to ensure that an explanation of LOQs and nondetectables are provided with all reports and are uniformly used in data analyses (e.g., in averaging); a residue data management system that will improve the quality, accessibility, and comparability of food residue data, including those generated by the commercial sector; and a repository of information on the fate of compounds during food processing and preparation. Laboratories performing pesticide residue analysis for regulatory purposes should participate in QA-QC programs, including regular quality control checks by an independent, external organization.

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