particular application or are of insufficient frequency to capture durations of exposure concern (e.g., peak, 24-hour, 4-day) and are also temporally and spatially limited. Yet, monitoring data with adequate ancillary data and study design/objectives may be used quantitatively. Most commonly, monitoring data are used quantitatively when there are no methods available for modeling exposure or on a site-specific basis when monitoring data are available for a particular location. Quantitative use of monitoring data for risk assessment purposes includes the use of a measured concentration or an adjusted value [a factor30,31) measured concentration value adjusted (i.e., application of a bias to reflect uncertainties or inadequacies of the monitoring data to generate an exposure value] as a direct measure of exposure. Monitoring data are more likely to be used quantitatively as a local refinement given uncertainties in extrapolating results to other locations.

#### 4.2.2. Qualitative Use of Monitoring Data for Risk Assessment Purposes

If available monitoring data do not meet the standards for quantitative risk assessment use, it does not mean the data are not useful for risk assessment. Available monitoring data may still be valuable in adding context to the exposure assessments depending on the available ancillary data. For instance, detections of a given pesticide can provide a measure of a lower bound of exposure based on actual use or trends over time. While the data may not be sufficiently robust to ensure a high-end exposure has been observed, detected concentrations can confirm that pesticide(s) may be transported off a treated field. In addition, identification of pesticide co-occurrences (environmental mixtures) as well as the proximity of detections to species locations are useful information to include in characterizing the potential effects of pesticide use on non-target taxa. A comparison of model estimated and measured pesticide concentrations may be useful for characterization; however, unless the model is parameterized to simulate specific sampling sites, the degree of over- or under-prediction should be limited as model simulations are intended to be inclusive of vulnerable scenarios and are expected to be greater than measured concentrations. Nonetheless, all of this information may be used as part of a weight-of-evidence approach to support potential exposure pathways as well as exposure concentrations. Monitoring data that provide no context on where samples are taken, what the study objectives are, what analytical methods are used, or what the detection limits are should be mentioned; however, these data should not be used in a qualitative manner. When examining multiple sources of monitoring data, it is also important consider the potential for duplication (i.e., monitoring data reported for the sample study/sample in multiple databases).

#### 4.2.3. Future Enhancements in Quantitative Use of Monitoring Data for Risk Assessment Purposes

Several tools are being investigated by USEPA that would allow for the consideration of using less robust monitoring datasets to inform the various lines of evidence being used to evaluate aquatic exposure.