Summary of Awards to Date

Development of a risk ranking tool for evaluating hazards and risks related to agricultural water subpart E


Jan. 1, 2024 - Dec. 31, 2025

Award Number


Funding Agency

University of Arizona

Amount Awarded



Channah Rock, Ph.D.
University of Arizona


Charles Gerba, Ph.D., Kerry Hamilton, Ph.D., Gail Rosen, Ph.D.


Recent revisions (proposed) to the FDA Food Safety Modernization Act Produce Safety Rule Subpart E shift away from traditional water quality testing of indicator bacteria to evaluate water quality, to a more risk-based approach of assessing potential hazards to agricultural water used in a preharvest environment. Historically, the FDA defined “adequate sanitary quality” using quantitative standards for microbial water quality and required growers to calculate their Geometric Mean and Statistical Threshold Value for each water source (<126 CFU/100 ml and <410 CFU/100 ml generic E. coli respectively). In the proposed revision, the farm must determine what is “safe and of adequate sanitary quality” by conducting an Agricultural Water Assessment or ‘AgWA’ to determine if water is safe for its intended use. An AgWA may include an evaluation of the following factors: Animal Impacts & Activities, Soil Amendments, Human Waste, Other Water Users, Other Potential Sources of Hazards, Crop Characteristics, Ag Water Use Practices, Environmental Conditions, and Other Relevant Factors. Of these factors, Crop Characteristics (including in the context of Ag Water Use Practices and Environmental Conditions) is a relatively novel consideration in the context of prior risk evaluation schemes applied to agricultural water (IFPA/Harmonized, WG/LGMA). While the proposed rule offers opportunities for increased flexibility for growers to meet the rule, concerns have been raised related to how industry will systematically move through an assessment, the expectation for growers to understand concepts of hazards versus potential risks, and ultimately how can/will the rule be implemented and enforced given its subjective nature. While the FDA published the Agricultural Water Assessment Builder ( to support industry, the builder is simply a set of questions with no risk ranking of growing practices or crop types, quantitative data, or survey logic built into the questionnaire. To put it simply, unless better tools are developed, risk-based decisions will be driven largely by perception of risk rather than by scientific data/assessment.

Technical Abstract

To enhance industry and regulatory confidence in making risk-based decisions on agricultural water and its use, our team proposes to build a risk ranking tool, backed by Quantitative Microbial Risk Assessment (QMRA), that allows users to identify hazards and practices that increase potential risk (soil amendments of animal origin, overhead irrigation, surface water) as well as mitigation strategies that reduce risk (change in irrigation method, inclusion of agricultural water treatment, die-off) applicable to their production system. This proposal aims to use historical laboratory and field data coupled with QMRA to quantify the impact of microbiological risk due to growing practices outlined by FDA in proposed subpart E. This effort to develop resources for industry will enable improved evaluation of the impact(s) of crop characteristics, among other factors, on risk posed by agricultural water use during production of covered produce and provide scientific evidence to aid in risk reduction and support regulatory compliance.