The Food Quality Protection Act: An Industry Perspective of Aggregate Exposure Assessment. C. S. Barrow and B. Shurdut, Dow AgroSciences, Indianapolis, IN, 46268; C. Breckenridge, Novartis, Greensboro, NC, 27420; R. Layton, DuPont, Wilmington, DE, 19898; R. Jones, Rhone-Poulenc, Research Triangle Park, NC, 27701; and D. Robinson, International Life Sciences Institute, Washington, DC, 20036
Aggregate exposures should proceed using a tiered process. For lower tier assessments a deterministic approach will suffice if the estimated exposures are acceptable. However, a simplistic deterministic approach using point estimates will not adequately describe the frequency or range of potential exposures. As a result the use of probabilistic or distributional analysis is strongly preferred to quantify variability and uncertainty in a individual’s daily exposure estimate. Although target tissue dose is the most scientifically sound parameter for aggregation this information is generally unavailable. Thus, delivered dose becomes the preferred estimate of real world exposures. Estimating delivered dose requires the use of all high quality available data. For instance, in the case of exposure via drinking water existing data such as the Heidelberg College Water Quality Lab multi-year program can or USGS monitoring data be used to develop screening tools to estimate the distribution of drinking water contaminants in surface water. Detailed dietary assessment should include data for food residues, processing factors, and dietary consumption. Residue concentrations derived from food tolerances should be discouraged due to the general gross overestimate intrinsic with this type of data. In all cases, the percentage of crop treated should be taken into account. Care should be taken to remove or account for outliers in the current food consumption data sets. Non-dietary exposures necessitate consideration of dermal absorption, breathing rates, activity patterns, etc. The distinction between the presence of a chemical in a residence or on a lawn and its bioavailability must be understood and considered as part of the evaluation. Studies have been conducted which describe this proportionality through the concurrent assessment of surface and airborne measurements versus biological monitoring. Validation of aggregate exposures can be achieved by a combination of biomonitoring, whole body dosimetry, and environmental concentration measurements. Furthermore, surrogate data should be used to provide better estimates of exposure concentrations to obviate the need for extensive monitoring data programs which will likely produce little additional useful information.
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