NATIONAL PESTICIDE SURVEY
FUTURE ANALYSES AND RESEARCH
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NATIONAL PESTICIDE SURVEY
FUTURE ANALYSES AND RESEARCH
The Phase II analysis identified several topics and issues that the
Agency could undertake to evaluate further Issues are presented in four
major categories (A) Survey Design and Analysis, (B) Laboratory Methods, (C)
Data Collection and Field Assessments, and (D) Statistical Analysis.
(A) Survey Design and Analysis:
1. NFS stratification variables did not perform as anticipated.
Several research areas could provide useful guidance for States
and Regions. Development is required of better collection
methods, databases, and ground water sensitivity measures would
provide better data on pesticide use and sensitivity
2 Develop guidance for future state surveys of this type on survey
design, including tradeoffs between stratification, precision
requirements, and analytic methods.
3. Analyze aggregated databases such as RFF and NFERC/TVA with
respect to questionnaire items that were designed to obtain
essentially the same information Correlations can be reviewed
between aggregated data and questionnaire data and between
aggregated data and manufacturers' data.
4. Evaluate FRDS as a frame for future studies, and obtain additional
information pertaining to Community Water Systems, including data
on populations, mixing of water from different sources, and
grouping of wells.
(B) Laboratory Methods:
1. Review NFS chromatograms (primary and secondary, and particularly
Methods 1 and 3) to try to model the data differently
i. Perform evaluation of chromatograms for all NFS primary and
secondary columns to assess the full concentration
distribution for analytes that were detected at any level.
ii. Perform evaluation of chromatograms for spiked samples to
characterize the precision associated with analyte
concentrations at various levels.
2. Prepare statistical guidance for EPA laboratories for reporting
data without MRLs.
C) Data Collection and Field Assessments:
1. Resample NFS sites where pesticide detections occurred and
characterize recharge areas.
2 Carry out site-specific soil profiles at NFS sites where pesticide
detections occurred.
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3 Carry out time-series analysis for a select number of wells to
examine annual and seasonal effects.
(D) Statistical Methods.
1. Develop statistical methods, including Bayesian methods, for
combining the information contained in other state surveys and the
Pesticides in Ground Water Database
2 Develop diagnositic statistics for methods of logistic regression
analysis of survey data (i.e., SUDAAN needs to be substantially
improved to be useful).
3. Analyze effects of Survey weights:
i. Compare weighted results using Taylor linearization (SUDAAN)
to resampling techniques (WESVAR)
ii. Develop Bayesian methods for analyzing the Survey data
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