In November 2016, the U.S. Food and Drug Administration (FDA) finalized the Produce Safety Rule, which includes an Agricultural Water Provision (AWP) requiring that growers identify, inspect, and monitor their irrigation water supplies for indicator E. coli. Compliance for all aspects of the rule was set to begin in January 2018. However, in March 2017 the FDA made an announcement that it was reviewing the AWP after increasing pushback and confusion over some of the finer points of the provision. In the end, it kept the criteria the same but pushed the timeline for compliance out an additional 4 years and continued to emphasize the possibility of refinement as more science becomes available. Therein lies the rub.

Most people recognize that monitoring the water supplies that come into direct contact with fresh produce is a good idea. The problem that the FDA has encountered, one echoed by the scientific community, is that there are currently not enough data available to create a truly science-based standard for irrigation water. That does not mean that the regulation of water has no basis in science, but rather that the science of irrigation water has lagged behind that of other water types, like drinking or swimming. Why is that? Because research is hard and expensive and takes a considerable amount of time before concrete answers may be had, if any ever are. Further, funding for research is frequently driven by demand, and until recently, the demand for research linking microbial contamination of irrigation water supplies to risk of human illness in the United States has been low. However, as outbreaks of illness associated with consumption of fresh produce have increased, so too has public awareness of produce production environments, placing irrigation supplies in the crosshairs.

The microbial quality of irrigation water supplies is at the heart of the matter. Most bacterial, protozoal, and viral pathogens that have been associated with foodborne outbreaks are readily dispersed via water, so surface water distribution networks can spread localized sources of pathogens across large areas. If a grower’s irrigation source is contaminated, pathogens may be broadcast throughout a field, creating contact with many pieces of produce, and eventually resulting in an outbreak. These, among other qualities, make water a perfect vehicle for pathogens, making their regular monitoring beyond a good idea, but a necessity. The problem is deciding what to monitor for, which forces the underlying question: What makes people sick? The answer is: Many things! However, pathogens are relatively rare, and monitoring for a rare thing is not only time consuming, but also expensive. So many agencies choose to monitor for indicator organisms that occur in high concentrations inside human and animal guts. To protect the public, standards are frequently set at concentrations associated with human illness. For example, the standards in the AWP come from the U.S. Environmental Protection Agency and state that approximately 36 in 1,000 people exposed to water with an average generic E. coli concentration of 126 CFU/100 mililiters are likely to become ill. It does not say guaranteed, nor does it say ill with what. This estimation is the result of decades of research and is still regularly evaluated. To date, no study has been conducted to approximate the likelihood of illness in people that consume fresh produce that has been irrigated with water at different indicator E. coli concentrations.

Before the hard work of understanding risk to consumers can be done, however, we need to first understand the quality of irrigation water supplies across the United States. This is where irrigation districts in California and Washington have been helping. Following the release of the Produce Safety Rule and the subsequent AWP, my colleagues and I began actively pursuing IDs across the western United States as partners in research. Since that time, we have successfully completed a multistate survey of indicators and pathogens in surface irrigation water supplies, followed by a multiyear study to validate the use of data sharing as allowed under section 112.47(a)(2) of the rule.  Specifically, this provision allows growers to collaboratively monitor their water supplies, provided there are no reasonably foreseeable sources of contamination in between monitoring locations. In short, this means that growers along an irrigation canal or a piped lateral can all share their data and dramatically reduce the burden on any one grower. Without preliminary data, however, it is unclear how far away growers can be from one another and still collaborate, or even which factors along a canal should be considered “reasonably foreseeable sources of contamination.” We are actively analyzing our data collected from eight districts over 3 years to provide guidance on these questions and help growers begin the work of complying with the AWP. But much more work remains.


The microbial quality of irrigation water supplies is at the heart of the matter.



Though we currently enjoy ample participation, it took us years to gain the trust of enough districts to make a robust study possible. In western states, irrigation districts are a gateway that researchers must pass through to gain access to surface water distribution networks. Though the AWP places the sole responsibility of water testing on the grower, in the West, the source of many growers’ water is under ID control. Partnering with IDs is also much more efficient for researchers, since districts already have a built-in relationship with growers and can act as honest brokers of information. However, fear of potential liability has led some districts to respectfully decline opportunities for FSMA-related collaboration. Thus, the science of agricultural water tends to be concentrated in a few research-friendly IDs, reducing our ability to capture the broad diversity of agricultural water conditions experienced by the majority of produce growers. Even with access and helpful partners, public funding for this type of research is extremely limited, and research takes time. Again, districts may be able to help by lobbying state and federal legislators for increased funding for rigorous, and ultimately publishable, research within surface water irrigation supplies. But for now, growers and regulators will have to make do with the best available research and hope for better.

Dr. Melissa Partyka is an extension specialist at Auburn University and is an affiliate for the UC Davis Western Institute for Food Safety and Security. She can be reached at