Residue estimating exposure

Exposures of Children. Data need to be developed to properly assess the exposure of infants who eat processed baby foods containing residues of pesticides such as endosulfan. Several studies have estimated exposure based on endosulfan concentration found in foods typically eaten by infants however, no studies that directly studied infant exposure could be located. Attention should also be given to infant formulas and to the tap water used to prepare infant formulas from condensed or powdered forms. More data are also required to properly assess endosulfan exposure to children who live, play, or attend school near farmlands that are treated with endosulfan. Maps that catalog endosulfan use on crops and present average application rates would better allow an assessment of the potential for children in farming communities to be exposed. The possibility that farming parents work clothes and shoes may carry endosulfan residues into the home also should be studied. In addition, home use of endosulfan, which may result in exposure of children, needs to be investigated. 

Based on the patch method to assess worker or re-entry exposure, researchers have developed a database, which may be used to estimate exposure. Each patch from an individual in a study can be entered into the database separately, the residue data from patches from various body areas can be summed to yield a whole-body exposure number, and the data may be sorted as to worker tasks, equipment used, protective clothing worn, formulation types and other parameters. This is the basis for the currently used Pesticide Handlers Data Base (PHED), which was developed through a joint effort in the 1980s of CropLife America [formerly known as American Crop Protection Association (ACPA) and National Agricultural Chemicals Association (NACA)], the Environmental Protection Agency (ERA) and Health Canada. " The PHED is discussed in detail in another article in this book. 

The FDA and EPA recognize that the diets of infants and children may differ substantially from those of adults and that they consume more food for their size than adults. As a result, they may be exposed to proportionately more residues. The FDA and EPA address these differences by combining survey information on food consumption by nursing infants, non-nursing infants, and children with data on residues to estimate their dietary exposure. The FDA and EPA also use this process to estimate exposure for other age groups, as well as several different ethnic groups and regional populations. 

This document deals only with estimating exposure to direct additives and chemical contaminants. The procedures used to estimate exposure to chemical contaminants in food (including naturally occurring toxicants, such as mycotoxins) are essentially the same as those used for direct additives. Thus, contaminants will be considered in the discussion of direct additive exposure estimation. The procedures discussed herein are equally applicable to color additives, GRAS substances, prior-sanctioned ingredients, and pesticide residues. 

The primary role of SPMDs and other passive samplers is to provide convenient, powerful analytical tools for determining dissolved and vapor phase HOC concentrations in environmental systems. This chapter has shown that they are also useful as biomimetic screening tools for estimating exposure of organisms to bioconcentratable compounds and for deriving BCFs based on EP theory. Even for those chemicals that are present at vanishingly small amounts in the dissolved phase and are primarily accumulated via the dietary uptake, SPMDs generally extract sufficient amounts of residues for analysis. 

Another example of exposure and corresponding risk reduction using Tier III methodology is provided in Table 27.4 for simazine (the triazine with the most registered uses in the United States). The Tier III analysis - using average field trial residues, realistic residue estimates in animal commodities, and percent of crop treated - showed at least a 1000-fold reduction in exposure for the United States population and for the most sensitive population subgroups as compared to the tolerance-based Tier I assessment. 

However, when the LOQ of a method is significantly lower than the actual concentrations monitored for compliance with a MRL, it may be more appropriate to carry out the validation experiments based on a lowest calibrated level (LCL), typically 0.5 x the MRL. For use in a regulatory program, the limits of detection and quantification are important parameters when the method will be applied to estimate exposure to residues, where there may be an interest in monitoring residues at concentrations below the MRL, or when conducting residue analyses for substances that do not have ADIs or MRLs. For monitoring compliance with a MRL, it is important that an LCL be included in the analysis that adequately demonstrates that the MRL concentration may be reliably determined. The LCL of a method used to support a MRL should not be less than the LOQ. 

Pcslieide residues on foods Estimated 6000 oanoers annually, based on exposure lo 200 potential onoogens. 

Serum endosulfan was 4 pg/L at 30 hours after an agricultural pilot was exposed dermally (and probably also by inhalation) for approximately 45 minutes in clothing that was heavily contaminated with endosulfan and methomyl (Cable and Doherty 1999) the dermal exposure level was not estimated and no other measures of tissue levels of endosulfan were obtained. A study by Kazen et al. (1974) has identified endosulfan residues on the hands of workers after relatively long periods free from exposure. Endosulfan residues were identified on the hands of one worker approximately 30 days after exposure and on the hands of one worker who had not used endosulfan during the preceding season. 

The degree of confidence in the final estimation of risk depends on variability, uncertainty, and assumptions identified in all previous steps. The nature of the information available for risk characterization and the associated uncertainties can vary widely, and no single approach is suitable for all hazard and exposure scenarios. In cases in which risk characterization is concluded before human exposure occurs, for example, with food additives that require prior approval, both hazard identification and hazard characterization are largely dependent on animal experiments. And exposure is a theoretical estimate based on predicted uses or residue levels. In contrast, in cases of prior human exposure, hazard identification and hazard characterization may be based on studies in humans and exposure assessment can be based on real-life, actual intake measurements. The influence of estimates and assumptions can be evaluated by using sensitivity and uncertainty analyses. - Risk assessment procedures differ in a range of possible options from relatively unso-... 

One common objective of an LSMBS is to refine the estimates of actual exposure of consumers to ingredients or impurities in one or more products. For example, study results might be intended to determine a realistic human dietary exposure to pesticide residues in fresh fruits and vegetables. The advent of the Food Quality Protection Act of 1996 (FQPA) has produced an enhanced focus on the exposure of children to pesticides. A well-designed and implemented LSMBS would afford the opportunity to delineate better the exposure and risk to children and other population subgroups. The LSMBS would provide consumer-level data at or near the point of consumption, allowing the refined, relevant, and realistic assessments of dietary exposure. 

OPMBS data were intended to support a valid estimate of the dietary exposure of populations and sub-populations to organophosphate residues in fresh fmits and vegetables. The results of the study were presented to the EPA in a report, with appropriate summaries. All of the study results, i.e., residue levels of each compound determined in each sample of each commodity, were also provided to the EPA in a database. EPA has recently notified the task force that the OPMBS study on the frequency and magnitude of organophosphate residues in fruits and vegetables is acceptable. The EPA is expected to utilize the data in a new assessment of potential dietary risk from organophosphate residues. 

Distributions of pesticide concentrations in potential food items for avian species are required to estimate the contribution of food to exposure of birds in different regions where the test chemical may be used. On treated fields, detectable CEF residues were found in 102 of 207 earthworm samples. No earthworm samples collected from control fields (N = 28) contained detectable CEF. Average CEF concentrations in earthworms reached maxima 1-4 days post-application (Table 3). Mean CEF residues in earthworms fell below 0.1 qg g after 8 days post-application. This... 

Data collected in drift studies may later be interpreted in risk assessments in conjunction with toxicity data for specific sensitive areas. Eor example, a risk assessment for determination of appropriate mitigation (if necessary) may include field study data on exposure risk from drift, along with information on other routes of exposure (e.g., dislodgable residues, runoff, etc.) and toxicity data from laboratory and/or field study models. The results of such an assessment may be used to estimate whether a given exposure represents a hazard to any specific entity or ecosystem. 

Among the first dermal dosimeters used in exposure research were 4 x 4-in cellulose or gauze patches which were pinned to the outer and inner surfaces of clothing or vests which farm workers would wear during the application or re-entry phase of the smdy. These patches were easy to manufacture and when pinned to the shirt or pants of the worker made for an easily used dosimeter pad. The major advantage to the use of the patch to estimate worker exposure was this method s ability to differentiate the relative contributions of pesticide residues to different parts of the worker s body. This sampling technique in turn could lead to recommendations (i.e., the use of... 

Doses of chlorpyrifos in human volunteers were also estimated using physical measurements. Air sampling was conducted in order to estimate the inhalation dose to each volunteer. Dislodgeable residues were also measured throughout the study to estimate the dermal contribution to total dose. Finally, hand rinses were conducted on each volunteer immediately following the 4-hr activity period to assess the potential contribution to total dose from hand exposure and to estimate an oral dose to a crawling child. 

Note Values of 1/2 limit of detection were used to estimate the exposure in cases where no residues were detected. Trace values below the limit of detection were used (e.g., trials 4 and 10). The limit of detection for TDX was 30.5 frg, and the limit of detection for REX was 5.4 frg/day, making the limit of detection for REX 35.9 frg/day... 

When humans contact a chemical residue such as a pesticide on a treated surface, some of the deposit can be dislodged or transferred to skin or clothing. Ultimately, a portion of the amount transferred may be absorbed and constitute the absorbed daily dose (ADD). The ADD provides the most precise estimate of exposure that can be practically obtained for humans and has become the most useful expression of exposure for risk assessment and risk management. 

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