Water sampling for Food Safety Modernization Act compliance

Recently, the U.S. Food and Drug Administration (FDA) published the Food Safety Modernization Act (FSMA) Final Rule on Produce Safety. One area that was tweaked in the final rule from the proposed rule was clarification around sampling when testing irrigation water for fresh produce.

Recall that the FSMA classifies two types of water used in the field: agricultural and indirect water. If water comes into direct contact with the harvestable portion of a plant, it is considered agricultural water. If a grower uses overhead sprinklers to irrigate a lettuce field, it would be considered agricultural water. In the case of indirect water, the water would not come into direct contact with the harvestable portion of the plant. If drip tape under plastic is used to maintain tomato plants, this would be considered indirect water.

Under FSMA, water testing is only required for agricultural water. How often a grower needs to test irrigation water that will be used as agricultural water is determined by its source. Surface waters are to be tested at least five times per year, as close to harvest as you can, but not all at the same time. Well water is proposed to be tested four times the first year, then once annually after that. The FDA will be working with the U.S. Department of Agriculture and others to bring sampling numbers required of Good Agricultural Practices standards into line with FSMA standards.

In both cases, the testing of the last four years is aggregated to create two numbers: the standard threshold value and geometric mean. 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. This testing and computation is for agricultural water ONLY. Indirect water is not required to be tested, regardless of the source.

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. Michigan State University Extension encourages interested individuals to take time to educate themselves about the revisions. To read more about the rule, visit FSMA Final Rule on Produce Safety.

If you have specific questions about the produce rule or have difficulty tailoring GAPs to your farm, contact the Agrifood Safety Work Group at gaps@msu.edu or 517-788-4292.

— Phil Tocco, Michigan State University Extension