Pesticides in the Diets of Infants and Children (1993) / Chapter Skim
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7 ESTIMATING EXPOSURES
7 ESTIMATING EXPOSURES
Pages 267-322
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From page 267... ...
Dietary exposure to pesticides depends both on food consumption patterns (Chapter 5) and on residue levels on food (Chapter 6~.
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From page 268... ...
The statistical convolution methods that can be used for this purpose are discussed later in this chapter. Since ingestion of pesticides is dependent upon both food consumption and pesticide residue levels in food, it follows that the quality of dietary exposure data is determined by the quality of consumption and residue data.
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From page 269... ...
Note that although the focus is on the average daily ingestion by individuals over an extended period, the daily ingestion will vary from person to person, depending on their food consumption habits and the residues of benomyl in the foods consumed by each person. Since residue data were available for apples, grapes, oranges, peaches, and tomatoes, this example was used to illustrate the estimation of total exposure to a single pesticide from multiple food commodities.
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From page 270... ...
In contrast to benomyl, where average daily exposures are of interest, individual daily intakes are examined in this example because of the acute toxicity of aldicarb. Part of the aldicarb residue data is derived from composite sampling, which may underestimate peak residues found in individual potatoes or bananas as a consequence of compositing prior to residue analysis.
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From page 271... ...
Since some foods will not be consumed at all by some individuals, estimates of average daily consumption based on all individuals in the sample will underestimate average consumption for the subpopulation of individuals who consume the food in question. For this reason, separate estimates of average daily consumption for "all children" and for "eaters only" are considered when estimating exposure.
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From page 272... ...
Residue Monitoring The point at which food samples are taken will influence the residue levels found. The highest residue levels generally occur immediately following application, and are reflected in field trial data.
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From page 273... ...
Although market basket surveys provide residue data under conditions designed to emulate foods as consumed, they are limited because they provide only composite sampling results on a few foods included in a typical meal. Most analytical methods for measuring pesticide residues in food are subject to an LOQ below which residue levels cannot be accurately determined.
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From page 274... ...
A conservative approach is to assume that all residue levels are present at the LOQ. Although this may provide an upper bound on undetectable residues, it is unlikely that all the samples for which no residue was detected actually contain residues equal to the LOQ.
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From page 275... ...
Thus, once the food consumption and residue distributions have been determined, the distribution of dietary exposures can be calculated (Figure 7-3~. The technical basis of convoluting two distributions can be described briefly as follows.
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From page 276... ...
With large distributions, the computation burden can be reduced by working with a random sample of both the consumption and residue data. The Monte Carlo approach (i.e., random sampling)
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From page 277... ...
In this case, a single point on the exposure distribution is estimated by randomly combining points from the consumption distributions for all foods of interest with points from the corresponding residue distributions (one for each food) , and then summing the total exposure across all foods.
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From page 278... ...
The Residue Data Five different sets of residue data on benomyl residues were reviewed by the committee for this example. They were results of field trials conducted by the manufacturer, results of a market basket survey conducted by the manufacturer, · 1988-1989 compliance and surveillance data collected by the Food and Drug Administration (FDA)
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From page 279... ...
279 a; o o a; cn o In U cn ~ o o \~h , .
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From page 280... ...
144% FDA MFT MMB Fl PEACHES FDA MFT l 1 ~ _ so% _ MMB Fl FDA MFT MMB Fl ORANGES L 100X' FDA MFT MMB 80 60 40 20 o 40 30 20 10 o GRAPES 92% FDA MFT MMB Fl TOMATOES Let 66%, ~ . DOC arc ~ _ 4% SAMPLES ~8 DETECTIONS FDA= Food and Drug Administration MFT = Manufacturer Field Trial MMB= Manufacturer Market _ o% I Basket Fl Fl = Food Industry Organization FIGURE 7-4 Number of benomyl samples and detections in apples, grapes, oranges, peaches, and tomatoes.
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From page 281... ...
Note that different foods would be included with different residue data sets, depending on the availability of residue data for those foods. Finally, the distribution of average daily exposure from all foods combined across individuals was calculated.
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From page 282... ...
Estimates of young children's benomyl exposure based on the manufacturer's field trial residue data are almost identical, regardless of whether a value of zero or the LOQ is used in exposure calculations when no residue is detected. Estimates based on the manufacturer's market basket data are also comparable, regardless of the value assigned to nondetectable residues.
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From page 283... ...
. A Certification Business The committee obtained residue data from a certification business operating in California, a commercial organization that guarantees to grocery store owners and consumers that any residues in produce will be below
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From page 284... ...
284 / PESTICIDES IN THE DIETS OF INFANTS AND CHILDREN 100 80 60 40 20 100 Manufacturer - Manufacturer o ~ ; 20 ~ hare 0 1 2 345 6 78 91011 12>12 ~ 100 C' a' 3 80 60 40 20 a' it_ Do 100 o 80 60 40 20 o 0 1 2 3 45 6 7 8 91011 12~12 100 - FDA 80 ~0 0 1 2 3 4 5 6 7 8 9 10 1112 >12 Certificatic~n B'~in~ 0 1 2 3 4 5 6 7 8 9 1011 12>12 Food Industry 2 3 4 5 6 7 8 9 10 11 12 >12 1 | 1 5 year olds 4 year olds 3 year olds 2 year olds I year olds Exposure (pg/l |
From page 285... ...
FIGURE 7-6 Daily exposure of l- to 5-year-old children to benomyl in different combinations of foods, as shown by residue data from a certification business, FDA, the food industry, and the manufacturer (fields trials and market baskets)
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From page 286... ...
Both the manufacturer's market basket and the certification business's residue data show relatively small total residue exposures. Finally, Figures 7-5 and 7-6 show that assigning a value of
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From page 287... ...
Certain impacts on exposure estimates would be seen for pesticides where a relatively low number of samples contained detectable residues. SHORT-TERM EXPOSURE TO ALDICARB The Compound The evaluation of short-term peak exposures is illustrated using data on aldicarb residues in potatoes and bananas.
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From page 288... ...
lbe Consumption Data Data on consumption of bananas and potatoes by children between 12 and 24 months of age were obtained from the 1977-1978 NFCS. The mean, median, and 90th and 95th percentiles of the average daily consumption of bananas and potatoes are shown in Table 7-3.
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From page 289... ...
The Residue Data Until the early 1980s, residue sampling focused on aldicarb rather than on aldicarb sulfoxide-its persistent and more toxic metabolite. Furthermore, only composite samples were used.
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From page 290... ...
This difference is due largely to the use of field trial data for potatoes, which were obtained from crops known to have been recently treated with aldicarb. Effects of Assumptions Regarding Residues Below the LOQ The implications of results below the LOQ for exposure estimation can be illustrated using data on the levels of aldicarb in bananas obtained from the 1987 National Aldicarb Food Survey.
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From page 291... ...
This underestimates actual residue levels because compositing masks any unusually high residue levels on individual bananas in a given batch. Let us also assume that individual bananas testing negative do not contain residues above the LOQ.
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From page 292... ...
The discrepancy between these two values is particularly large for the subgroup of banana eaters only with nondetectable residues assigned a value of 0. Thus, esti TABLE 7-8 Daily Intake of Aldicarb from Bananas for Children Between 12 and 24 Months of Age Value Used for Intake, ,ug / kg bw / day Subsample Residues Below LOQ Mean Median P90 P95 All LOQ 0.015 0.002 0.034 0.058 0 0.007 0 0 0.008 Eaters only LOQ 0.025 0.005 0.050 0.087 0 0.012 0 0.003 0.032 SOURCE: Based on data from the 1987 National Aldicarb Food Survey and USDA's Nationwide Food Consumption Survey, 1977-1978.
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From page 293... ...
This method is most appropriate for estimating the average daily ingestion of pesticide residues over an extended period. Although average daily ingestion is an appropriate measure of exposure for chronic risk assessment, a different approach is required for acute toxic effects caused by short-term exposure to relatively high levels of substances.
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From page 294... ...
The distribution of aldicarb intake from both bananas and potatoes Food TABLE 7-12 Average Daily Intake of Aldicarb for Children Between 12 and 24 Months of Age Intake, fig / kg bw / day Mean Median P9O P95 Bananas 0.007 0 0 0.008 Potatoes 0.172 0 0.302 0.673 Bananas and potatoes 0.179 0 0.327 0.705 SOURCE: Based on data from the U.S. Department of Agriculture's Nationwide Food Consumption Survey, 1977-1978, the 1987 National Aldicarb Food Survey, and survey data from the pesticide manufacturer.
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From page 295... ...
FIGURE 7-7 Distribution of the average daily intake of aldicarb from bananas and potatoes, separately and combined. SOURCE: Based on data derived from USDA, 1983, the National Aldicarb Food Survey, and survey data from the manufacturer.
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From page 296... ...
Summary Aldicarb was examined by the committee because it is an acutely toxic chemical that may potentially be found in several foods consumed by children and because there were also good sampling data for aldicarb residues in several commodities. This example could also be used to illustrate approaches to estimating residue concentrations in both individual foods and in multiple?
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From page 297... ...
. This method was used to determine how many children are likely to be exposed to unsafe levels of multiple pesticides with that common effect and to express the exposures in the most desirable for~person-day exposures using actual individual daily consumption data and actual residue data.
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From page 298... ...
Estimating pesticide exposure in this way was considerably constrained by the absence of residue data for certain foods and compounds, especially processed foods such as juices whose type of processing could greatly influence pesticide residue levels. There are few available residue data for processed foods; thus, little is known about the effects of processing on pesticide residues.
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From page 299... ...
K 80 ~ 60 C' a, a, 40 G · - 20 ORANGE JUICE At__ H Intake (g/kg low/day)
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From page 300... ...
Nevertheless, ChE inhibition can occur, producing signs and symptoms of poisoning after exposure to small repeated doses. Long-term effects of acute and subchronic exposures to pesticides have been reported.
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From page 301... ...
The ratio of the chlorpyrifos NOEL to the NOEL of a different chemical (chemical X) provides an estimate of relative potency for chemical X and was used to adjust the laboratory-detected residue levels of the five chemicals of concern (Tables 7-14 and 7-15~.
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From page 302... ...
: EPA, July 1992. TABLE 7-15 Estimates of Toxicity Equivalence Factors for Five Organophosphate Insecticides Using the NOAEL for Chlorpyrifos as the Reference Standard NOAEL Pesticide NOAELa Ratio = TEF Acephate NA NA Chlorpyrifos 0.03 mg/kg bw 1 Humans, ChE inhibition Dimethoate 0.05 mg/kg bw 0.03/0.05 = 0.6 Rats, Che inhibition Disulfoton NA NA Ethion 0.05 ma/ kg bw 0.03/0.05 = 0.6 Humans, ChE inhibition NOTE: NA, not applicable.
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From page 303... ...
This approach may result in an overestimation of actual exposure, since there is likely to be some correlation among residue levels of the different compounds. In particular, substitution among chemicals would lead to scenarios in which all five compounds are never detected on the same sample.
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From page 304... ...
Since the FDA does not record the LOQ for each sample tested, it estimated an average LOQ of 0.01 ppm for all chemicals and foods analyzed in this study and proposed that this value be used in the committee's analysis. Exposure Analysis The objective of this exposure analysis is to produce a distribution of possible person-day exposures based on the food consumption data for 2-year-old children, including 1,831 person-day intake values for eight foods and eight separate residue distributions representing cumulative exposure-one for each of the eight foods.
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From page 305... ...
The committee does not believe that the data used do accurately represent the current status of those pesticide residues on foods because of the age of the consumption data, sample sizes, and the methods used by the FDA in interpreting residue values beneath an "action" or legal tolerance level. However, these data sets are the best now available 100 95 cat 90 Or 85 ._ ~ 80 a)
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From page 306... ...
The results of the analysis are shown in Figure 7-11. The primary finding of this analysis is a shift in the distribution to higher residue levels.
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From page 307... ...
NONDIETARY EXPOSURE TO PESTICIDES Although it was not generally within the committee's charge to examine exposures to pesticides by routes other than dietary, the committee wishes to point out that infants and children are subject to such exposures from a variety of sources. These sources should not be overlooked when attempting to estimate the total exposure of infants and children to pesticides and are therefore briefly summarized in this section.
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From page 308... ...
Concentrations of 0.2 ,ug/m3 of Telone in air are associated with cancer risks of 1 in 100,000 over 70 years, according to the EPA and the California Department of Health Services (CDHS)
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From page 309... ...
In rural areas, where residue levels were higher than in urban areas, the highest concentrations were found where spraying was reported (Arthur et al., 1976~. Indoor Air The widespread use of pesticides such as flea bombs and insecticide sprays and loggers in the home exposes children to pesticides in their indoor environment.
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From page 310... ...
analyzed in EPA's NOPES study, the mean air exposures were always or often higher than the estimated dietary exposure for the same compounds (EPA, 19901. Fenske et al.
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From page 311... ...
Flea control products commonly used in veterinary clinics, pet stores, and other commercial establishments include carbaryl, chlorfenvinphos, chlorpyrifos, dimethyldichlorovinyl phosphate (DDVP) , fenthion, malathion, phosmet, and propoxur (Ames et al., 1989~.
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From page 312... ...
312 / PESTICIDES IN THE DIETS OF INFANTS AND CHILDREN Playground Equipment Wooden playground equipment is another source of pesticide exposure because of the various kinds of wood preservatives used to prevent microbial and insect attacks. A 1987 California survey estimated that approximately 20% of all wooden structures in parks were treated with chemical preservatives.
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From page 313... ...
The organophosphate pesticides diazinon and chlorpyrifos and several organochlorine pesticides such as dieldrin have been found at measurable levels in lanolin.
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From page 314... ...
· Dietary exposures to pesticide residues can vary widely. Since most pesticide residues in foods are below the analytical limit of quantification, with comparatively few high residue levels, the distribution of dietary exposure to pesticides includes many low intakes.
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From page 315... ...
· Average daily ingestion of pesticide residues is an appropriate measure of exposure for chronic risk assessment, whereas actual individual daily ingestion is more appropriate for acute risk assessment. Since chronic toxicity is often related to long-term average exposure, the average daily dietary exposure to pesticide residues may be used as the basis for risk assessment with delayed irreversible chronic toxic effects.
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From page 316... ...
· Intake of multiple pesticides with a common acute toxic effect can be estimated by converting residues for each chemical to equivalent units of one of the compounds. The standardized residues can then be summed to estimate total residue levels in toxicity equivalence factors, and then combined with consumption data to construct a probability distribution of total exposure to all pesticides having a common mechanism of action.
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From page 317... ...
· If appropriately designed and conducted, surveillance studies of pesticide residues in food provide unbiased data on residue levels in food products. Field trials are also useful sources of information on pesticide residues in food.
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From page 318... ...
can be used to impute residue levels below the LOQ provided that the percentage of the residue data lying below the LOQ is not large. The use of such methods can reduce the uncertainty in resulting estimations of human exposure.
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From page 319... ...
One possible approach is to establish toxicity equivalence factors based on no-observedeffect levels as was done for organophosphates in this chapter. · Because infants and children are subject to nondietary sources of exposure to pesticides, it is important to consider total exposure to pesticides from all sources combined.
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From page 320... ...
1990. Pesticide Safety Information Series A-7, California Department of Food and Agriculture Worker Health and Safety Branch.
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From page 321... ...
1986. Toxic effects of pesticides.
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From page 322... ...
1987. CSFII, Nationwide Food Consumption Survey, Continuing Survey of Food Intakes of Individuals, 1985.
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