Proposed revised irrigation water standards for FSMA

Proposed Food Safety Modernization Act water standards have recently changed and are important to be aware of. This article outlines a small portion of the newly proposed water standards and gives information about how to comment.

The proposed Food Safety Modernization Act (FSMA) is the most sweeping legislation regarding raw agricultural products in 70 years. Recently, the FDA published revised rulemaking in a number of areas. One area that was revised significantly was irrigation water testing for fresh produce and what standard to use when testing water.

The new revision proposes the use of the 2012 Recreational Water Quality Criteria (RWQC) as a standard for generic E. coli when applying water directly to the edible portion of the plant. For reference, the standard is no more than 410 colony forming units (CFU) of generic E. coli as a Statistical Threshold Value (STV) and a geometric mean of 126 CFU. This standard is very different than the earlier proposed standard and is quite a bit more difficult to understand and calculate in large part because of the testing frequency needed to generate these numbers. (To avoid confusion, growers should note the EPA RWQC found in the FSMA is more stringent than Michigan’s body contact standard of 300 CFUs.)

To tease apart the various aspects of this standard, Michigan State University Extension will be publishing a number of short articles that will break down the standard and allow for better understanding. Each article is a piece of the rule. All the articles must be taken together for a comprehensive understanding of what is proposed for water.

The standard is based on a geometric mean. This is not an average. A geometric mean is the root number of the product of all the test results. So if one were to calculate the geometric mean of two numbers, they would multiply them together, and then take the square root of that product. When calculating the geometric mean of three numbers, they are multiplied together and the cube (third) root of the product is calculated. It can be very complicated when dealing with more than three values. FDA has already talked about setting up tools to help growers calculate these values.

With regards to the Statistical Threshold Value, this is a number that represents the 90th percentile of all the values of test results. The goal is that if you were to have taken 20 water samples, only two would have been higher than this number. This is more flexible, because it allows for bigger spikes in water quality. The FDA will be creating a tool to help growers with this component. These values must be recalculated every 10 years or sooner if the values for a given year deviate significantly from the established baseline.

This discussion is not a comprehensive look at the changes to FSMA in the proposed revisions or even in the changes to the water quality section in fresh produce. I encourage interested individuals to take time to educate themselves about the revisions and comment. You can submit comments online. Comments can also be written and faxed to the FDA at 301-827-6870 or mailed to:

Division of Dockets Management (HFA-305)
Food and Drug Administration
5630 Fishers Lane, Room 1061
Rockville, MD 20852

Read more about the FSMA rule and how to comment on the proposed rule. If you have specific questions about the produce rule or have difficulty tailoring GAPs to your farm, contact the Agrifood Safety Work Group at or 517-788-4292. 

Additional articles in this series:

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