Currently drinking water assessments conducted in the United States use conservative assumptions with mechanistic models.  These procedures show adequate dietary safety for most compounds and are reasonable as an initial screening approach.  However, higher tier options are needed for more realistic assessments for some compounds.  For drinking water from surface water, potential approaches include more realistic use assumptions while recognizing the variability of use in smaller watershed, more realistic soil and water degradation rates when supported by field data, considering the variability of application timing in a catchment, accounting for the effect of water treatment processes, and considering reservoir and watershed geometry.  For drinking water from ground water, potential approaches include more realistic descriptions of degradation as a function of depth (when supported by field data, the use of DFOP kinetics (double first order in parallel) when applicable, use of Freudlich sorption, and considering time-dependent sorption (when supported by laboratory experiments).  Targeted and untargeted surface water monitoring programs and results of prospective ground water studies and terrestrial field dissipation studies can be useful in demonstrating the need to consider such refined modeling approaches and to show that the resulting assessments are conservative with respect to dietary exposure.  Development of additional crop-specific and geographically-specific scenarios can also be helpful when existing scenarios do not reflect actual use conditions.

Higher tier assessment options in drinking water assessments

254th National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.