Pesticide residues dietary exposure data

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. 

Dietary exposure to pesticides (or to xenobiotics in general) is determined by calculating the product of the amount of chemical in or on the food and the total quantity of food consumed. The quantity of chemical potentially consumed in foods can be estimated from data obtained from residue field trials, metabolism studies, and/or monitoring data. Information from these sources is then analyzed with one of several available models containing food consumption factors from surveys conducted by the United States Department of Agriculture (USDA). For calculation of... 

Dietary Exposure Potential Model (DEPM) Model and database system for deterministic dietary exposure Exposure from pesticides in diet combines food consumption and residue data USEPA (2003a)... 

Two types of dietary exposure are understood. Chronic exposure represents exposure to pesticide residues in food over a relatively extended time period, frequently assumed to be the course of a lifetime. In contrast, acute exposure represents exposure to pesticide residues in food over a relatively short time period, usually over the course of one day. Most of the significant differences between the EU and US approaches to dietary exposure analysis and risk assessment focus on acute dietary exposure. Some of the differences have their sources in the different types of data available in the two areas. Other differences have their sources in different regulatory policies or societal viewpoints. 

When calculating chronic dietary exposure, the deterministic models use point values for both food consumption and residue concentration, thereby yielding a point estimate of dietary exposure. In the US, the initial chronic dietary exposure estimate is the Theoretical Maximum Residue Contribution (TMRC) and is analogous to the Theoretical Maximum Daily Intake (TMDI) used to estimate chronic dietary exposure in the EU. Both the TMRC and the TMDI are relatively conservative estimates of dietary expostire. The TMRC is calculated as the product of the mean consumption value and the US pesticide tolerance [6]. In the EU, the TMDI is calculated as the product of the mean consumption value and the Maximum Residue Limit (MRL) [7]. The objective of both calculations is essentially identical to calculate an estimate of the central tendency of the dietary exposure. Both calculated values use the central tendency dietary exposure estimate as the estimate of chronic (long-term) dietary exposure and calculate it using mean consumption data and the maximum residue permitted on the commodity. 

Risk of dietary exposure to fenthion is largely due to potential residues in beef meat and fat while it can be excreted in cow s milk, US Department of Agriculture (USDA) analyses of close to 1300 samples yielded no detections. The US Environmental Protection Agency s (US EPA s) most recent re-registration documents contain data on potential dietary exposure, but these estimates have not been refined because of the change in use of the pesticide. 

U.S. EPA s Office of Pesticide Programs has used DEEM in its exposure and risk assessments. The Dietary Exposure Potential Model (DEPM) is another ingestion model that facihtates the correlation of food consumption data and chemical residue data (Cherrie et al. 2006 Tomerhn et al. 1997 US EPA 2003a). 

Secondly, a probabilistic (Monte Carlo) simulation was used. This considers a complete set of crop residue data and samples data points randomly. This approach is generally considered to be more Realistic for assessing dietary exposure to a pesticide. Tolerance assessments used TAS and DEEM in order to establish the safety of tolerances (MRLs or maximum residue limits) for cotton, potato and tomato and also to compare the output of the two programs. 

The new safety standard, provided in section 408(b) (2) (A) (ii) of the FQPA, is a reasonable certainty of no harm standard for aggregate exposure using dietary residues and all other reliable exposure information. When setting new or reassessing existing tolerances or tolerance exemptions under the new standard, EPA must now focus explicitly on exposures and risks to children and infants. EPA must explicitly determine that the tolerance, or exemption from tolerance, is safe for children consider the need for an additional safety factor of up to tenfold to account for uncertainty in the data base relative to children unless there is evidence that a different factor should be used and consider children s special sensitivities and often unique exposure patterns to pesticides. 

U.S. tolerances is the responsibility of the U.S. Food and Drug Administration (FDA). In the absence of a specific tolerance, residues must be below detectable levels. Based on modifications to FFDCA mandated by the Food Quality Protection Act (FQPA) of 1996, several new elements were introduced to the EPA tolerance process. These include the need to consider the special sensitivity of infants and children, the potential exposure via multiple routes of exposure (i.e., aggregate exposure from dietary and non-dietary sources), and the potential for exposure to other pesticides and chemicals with a common mechanism of toxicity (i.e., cumulative exposure). Under FQPA, the EPA was also required to complete a reevaluation of all existing tolerances during a 10-year period. Domestically established M RLs apply also to imported commodities, but there is an established (if somewhat slow) process for evaluation of residue data from other countries in support of import tolerances. 

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