The U.S. Food and Drug Administration (FDA) has released a risk assessment evaluating the potential for human illness associated with consuming produce grown using untreated biological soil amendments of animal origin (BSAAO), including raw manure.

The risk assessment examined how human pathogens, including Shiga toxin-producing Escherichia coli (STEC) O157:H7, non-O157 STEC, and Salmonella, may survive in untreated BSAAO and contaminate produce. According to FDA, pathogen survival and crop contamination risks depend on factors such as environmental conditions and agricultural practices.

FDA conducted the assessment in two phases.

1. Phase 1: Pre-harvest. The first phase evaluated pre-harvest practices and environmental conditions that influence the likelihood of produce contamination before harvest. It analyzed how interventions, including the waiting period between application of untreated BSAAO and crop harvest, affect pathogen concentrations on produce at harvest.
2. Phase 2: Post-harvest. The second phase modeled the movement of potentially contaminated produce through the supply chain to consumers. The model considered processing steps, cross-contamination risks during processing, transportation and storage conditions, consumption patterns, and the pathogen exposure levels required to cause illness.

The full risk assessment and related documents can be accessed on FDA's "Completed Peer Reviews" webpage.

Longer Times Between BSAAO Application and Harvest Reduce Pathogen Contamination Risk

FDA reported that extending the time between the application of untreated BSAAO and harvest significantly reduced the potential level of pathogens on produce at harvest. However, the effectiveness of longer intervals varied depending on the pathogen, the type of untreated BSAAO, environmental conditions, and the initial pathogen levels present in the manure.

The agency also said the risk assessment model could be used by industry and other stakeholders to evaluate risks associated with specific agricultural practices and environmental conditions.

Context for the Produce Safety Rule

The risk assessment relates to provisions in FDA’s Produce Safety Rule under the Food Safety Modernization Act (21 CFR Part 112). When FDA first proposed the rule in 2013, it included a nine-month minimum interval between the application of certain untreated BSAAO and harvest.

Following public comments calling for additional scientific evidence, FDA did not finalize that requirement. Instead, the final rule reserved a provision for a future standard pending the completion of a risk assessment.

With the publication of the assessment, FDA said it will consider next steps regarding potential standards for the use of untreated BSAAO in produce production and will continue engaging with stakeholders on produce safety.