ARTF conducted all of its exposure studies using test substances that were registered pesticides. One of the most difficult tasks in preparing for field studies was the identification, development and evaluation of appropriate surrogate compounds for measuring exposure. The surrogate compounds selected had the following desirable characteristics:
- Registered for use on many crops
- Relatively short Restricted Entry Intervals (REIs)
- Short Preharvest Intervals (PHIs) for harvest studies
- Stable under field conditions
- Relatively persistent residues on foliage
- Validated analytical methods that were practical, reproducible, and sufficiently sensitive for detection of the test substance in all types of experimental matrices.
- A potential surrogate was identified.
- Analytical methods were either developed (if none existed) or modified to accommodate the sensitivity required by ARTF studies.
- The analytical methods were validated in a study conducted under EPA Good Laboratory Practice Standards.
- The stability of the surrogate under field conditions was evaluated within a small field study.
- Freezer storage stability of the potential surrogate was also evaluated.