CA's Leafy Greens under Scrutiny; More Root-Cause Analysis Needed?

With the U.S. Food and Drug Administration's (FDA's) summer announcement that it will again conduct targeted sampling of leafy greens as part of its Leafy Greens STEC Action Plan (LGAP),¹ what does that mean for leafy greens growers? Farms and ranches located in the Salinas Valley may already have FDA officials on their land taking product samples—if the farms were identified through traceback investigations as being potentially associated with a foodborne illness outbreak.

In an effort to avoid the risk of Shiga toxin-producing Escherichia coli (STEC) contamination of leafy greens, FDA is concentrating its sampling efforts² on the California growing region, as it has been the source of several foodborne illness outbreaks across North America in recent years. Sampling began in mid-September 2022 and will run through October 2022, and all samples will be tested for several species of Salmonella and STEC. In addition to taking around 240 product samples, FDA may collect environmental samples such as water, soil, and animal waste, as appropriate, based on observations made at the time of sampling and a farm or ranch's past inspection history.

FDA's summary report³ for its 2021 Salinas Valley sampling, conducted from May through November of last year, resulted in three positive findings out of the 498 samples tested. FDA detected STEC in one red leaf sample and one iceberg sample, as well as Salmonella enterica subspecies diarizone (which is rarely associated with clinical illness) in one green leaf sample. In their 2022 meetings with leafy greens producers in California, FDA food safety experts will also explore concerns about the sanitary design of harvest equipment and how field production and processing practices may be contributing to contamination events—two complex areas that are worthy of closer examination through root-cause analysis.

Sampling helps identify if a problem exists. Root-cause analysis helps identify the changes that need to be made to prevent a problem from recurring. In the produce sector, root-cause analysis is more complex than for other food types due to the variable nature of environmental conditions and inputs in growing areas, as well as the ability of produce crops to be impacted by surrounding activities. Produce root-cause analysis is also made more complex by the highly perishable nature and variable characteristics of the products, the seasonally inconsistent nature of risks, the unique setup of each growing operation, the variability of monitoring equipment and record-keeping, as well as the difficulty of replicating preharvest conditions for performing the analysis.⁴ 

Amid these complexities, methods are available for systematic root-cause assessment and analysis that help identify the prevalence or proximity to hazards; the concentration of those hazards and probability of exposure to them; the outcome and severity of risk of exposure to the hazards; and the probability of contamination, recurrence, and spread. In produce, hazards identification does not always mean pinpointing one clear, singular factor as the cause of contamination. Many factors may work in concert to cause an issue. A number of complex and complicated interactions occur in a growing environment on a daily basis, and predicating factors may disappear over time, making it difficult to diagnose the original source of contamination.⁴

Root-cause analysis requires experience, critical reasoning, and an appropriate level of skepticism. While produce root-cause analysis is often not definitive, it is still an important tool to help mitigate the risk of contamination in leafy greens and the foodborne illness outbreaks associated with this food type.

References

1. FDA. "Leafy Greens STEC Action Plan." September 8, 2022. https://www.fda.gov/food/foodborne-pathogens/leafy-greens-stec-action-plan.
2. "FDA's Leafy Greens Action Plan: FY2021 Sampling Results, Future Targeted Sampling." Food Safety Magazine. September 8, 2022. https://www.food-safety.com/articles/7993-fdas-leafy-greens-action-plan-fy2021-sampling-results-future-targeted-sampling.
3. FDA. "Microbiological Surveillance Sampling: FY21 Sample Collection and Analysis of Lettuce Grown in Salinas Valley, CA." September 8, 2022. https://www.fda.gov/food/sampling-protect-food-supply/microbiological-surveillance-sampling-fy21-sample-collection-and-analysis-lettuce-grown-salinas.
4. Eurofins US Food Group. "Produce Industry Root Cause Investigation Webinar." Trevor Suslow, Ph.D., Extension Research Specialist, Department of Plant Sciences, University of California–Davis. YouTube. August 5, 2021. https://youtu.be/AhnSrX2j-KM.