Water quality is a key component of produce safety. It is so important that it is, undoubtedly, the most critical provision of the Produce Safety Rule of the Food Safety Modernization Act (FSMA). It also is the most controversial.

As mandated by the rule, produce growers are required to follow specific criteria for the microbial quality of their agricultural water — that is, any water that (1) could be directly or indirectly transferred to produce or (2) is directly applied to growing produce. Both sets of criteria are based on the presence of generic E. coli, which can indicate the presence of fecal contamination.

For potentially transferred water, the rule states that no detectable generic E. coli are allowed. These include such uses as handwashing during/after harvest, uses for which the water touches food-contact surfaces or produce (including ice), and sprout irrigation. If E. coli presence is detected, use must be immediately discontinued and corrective action taken. Untreated surface water cannot be used for these purposes.

The FDA is exploring ways to simplify the standards for water used in growing operations, such as in irrigation systems.

Complicated testing requirements

But it is the criteria for the testing of water that is directly applied to produce that is the most complex and has garnered the greatest dispute from industry. For these uses, the rule requires that first-year testing be conducted four or five times (depending on the source) and at least annually thereafter. Determination of contamination is then calculated by aggregating the testing of the last four years to create the standard threshold value and geometric mean.

As explained by the Michigan State University Extension Service:

“If a grower’s values for these two numbers are below a geometric mean of 126 colony-forming unit (CFU) per 100 milliliters and a standard threshold value of 410 CFU per 100 milliliters, then they continue to use the water as they have always done. Every year, the grower will compute a new geometric mean and standard threshold value by taking the last three year’s data and combining it with the current year’s data to compare it with the threshold values. If a grower’s numbers exceed the threshold, the grower needs to take measures to mitigate the potential contamination.” (

If this sounds like a foreign language to you, don’t be alarmed — you’re not alone. After receiving feedback from stakeholders that some of the agriculture water standards of the rule were too complex for the industry to understand, translate and implement, FDA announced that it is exploring ways to simplify the standards. To allow time to do so, the agency also will be extending the compliance dates for the agricultural water standards (except as it relates to sprouts).

Although the length of the extension is still “under consideration,” FDA intends to work with stakeholders as it considers the best approach to address their concerns while still protecting public health. The extension will also be helpful to the produce industry because, while the microbial quality standards for agricultural water are important for reducing the risk of produce-contaminating pathogens for which water can be a major conduit, many laboratories do not provide methods to test water to FSMA specifications.

Growers can follow current water quality testing recommendations until the final water quality criteria is released.

Controversial standards

There also is some controversy about the FSMA standards because some research has found that it is difficult to make a connection between water standards and pathogen levels. This is because water quality is most often assessed using indicator organisms which are not human pathogens. As discussed in a Penn State research paper (, testing for pathogens in water is difficult because it is very expensive and time consuming, requires specially trained personnel and equipment, and levels able to cause illness may be too low to be detected by standard methods. Thus, like the FSMA standard which tests for generic E. coli rather than the specific pathogenic strain, water quality standards generally rely on testing for indicator organisms, because their presence suggests probable presence of a pathogen. But, the report adds, testing water to see if it meets standards may not mean much in terms of actual pathogen presence.

While the report focuses primarily on surface water, it also notes that summaries of drinking water outbreaks in the U.S. between 1971 and 2008 show that bacteria are the most commonly implicated causes when a source is identified. Additionally, produce accounts for more outbreaks in the United States than any other food type, and while contamination can occur anywhere in the production system, irrigation water and manure are considered the most common sources.

Maintaining water quality

Despite any controversy of current and proposed agricultural water quality standards and FDA’s review of its criteria, produce growers should not simply wait out the extension. The time can instead be used to review your practices, processes and procedures related to agricultural water and how it is used and assessed.

Until we do get the final criteria, greenhouse growers can follow current water quality testing recommendations, such as those from the Alabama Cooperative Extension System ( for irrigation water:

  1. Have your irrigation water tested by a university or private laboratory any time a new water source is established and at least twice per year thereafter — or as frequently as needed to establish variability in water quality over time.
  2. One good approach is to test during a wet period, then a dry period because high rainfall can dilute water impurities and drought can concentrate them. Once a water quality pattern has been established, yearly testing is usually sufficient.
  3. To ensure the water samples reflect the properties of the water source before coming into the greenhouse facility:
    • Collect the sample as close to the sources as possible (e.g., well head or main inlet).
    • Allow the water to run long enough to flush the line, about five minutes.
    • Collect at least one pint of water in a new polyethylene or polypropylene plastic container or a boron-free glass container.
    • Avoid containers with metal lids or containers washed with phosphate-containing detergents.
    • Fill the container completely with water, allowing no air space, and seal the lid tightly.
    • Promptly send the sample(s) to an appropriate laboratory.

We are still awaiting further word from FDA on revisions to the water standards and timing of compliance. However, it is reassuring to hear the agency say that it understands the need to strike a balance between protecting public health and implementing rules that decrease burden and are workable across the diversity of the food industry.

Lisa is the editor of sister publication Quality Assurance & Food Safety (QA) magazine.

Read a letter to the editor about this article here.