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Contact Produce Safety Research logo Produce Safety Research

Contact Produce Safety Research logo Produce Safety Research


Below, you will find more information on each of the seven objectives.
Learn more about who is involved under How to Reach Us.

  • Objective 1 - Agricultural Water Treatment

    Find approaches to decrease introduction of microbial food safety hazards onto specialty crops from agricultural water. 

    Agricultural water practices hold some of the greatest concerns and confusion with regard to Produce Safety Rule implementation. Significant complexities, and knowledge gaps related to appropriateness of indicator organisms, sampling schemes, water treatment, and transfer of pathogens to and survival on crops exist. Growers are faced with myriad options related to water treatment and/or sanitization with very little guidance on the requirements needed for successful implementation of treatment. Water treatment decisions expend both time and money while failing to achieve a reduction in potential pathogens and indicator organisms within a water source given limited guidance.
    Additionally, significant gaps in our scientific knowledge associated with survival of bacteria, viruses, and protozoan parasites on leaf and fruit tissues following agricultural water treatment remain.

    Sub-objective 1.1.

    Evaluate microbiological indicators and pathogens (bacteria, viruses and protozoa) in irrigation water both pre- and post-treatment to assess performance of commercially available water sanitizers and pesticide application devices currently used by industry and to provide recommendations towards treatment efficacy and method validation.

    Sub-objective 1.2.

    Compare survival of E. coli and other select indictor organisms on leaves and fruits post-treatment to provide information for risk assessment and modeling.

    Concurrently with the above identified objectives, the research and extension team will work side-by-side with industry to inform research questions as well as to identify potential revised risk-based thresholds for indicator organisms in agricultural water. While water treatment can be an effective mitigation strategy to reduce microbiological hazards, it is important to note that it is not a risk elimination strategy. Scientific data from Objective 1 will specifically address current agricultural water metrics/regulations and provide context to their adoption with respect to actual human health risk.

    For more information, click here.


    Objective Lead

    Dr. Channah Rock, University of Arizona

  • Objective 2 - Biological Soil Amendments of Animal Origin (BSAAO)

    Develop new strategies to reduce introduction of microbial hazards into specialty crops via biological soil amendments of animal origin during production.

    Biological soil amendments of animal origin (BSAAO), like livestock manure, compost, and heat-treated amendments, are frequently used as organic fertilizers to improve physical and chemical properties and nutrient content of soils. BSAAOs are also a known reservoir for enteric bacterial pathogens like enterohemorrhagic E. coli and Salmonella. There are numerous mechanisms (splash, direct contact with soil, and dust) which transfer pathogens to fruits and vegetables, and foodborne outbreaks have been linked to manure-associated contamination of leafy greens with E. coli O157:H7. Soils amended with BSAAOs supply nutrients that enteric pathogens may utilize directly or indirectly to survive for extended durations. Past studies illustrate that amended soils extend survival of non-pathogenic E. coli compared to unamended soils. It has also been shown that regionality (climate, soil type, method of BSAAO application practices) greatly influences survival of pathogens in the soil, but no work has been done in the Southeast US that describes the effect of soil microbial diversity and communities on the predictability of enteric pathogens survival.

    Sub-objective 2.1.

    Identify factors affecting enteric pathogen survival in soils containing BSAAO in the Southeastern U.S.

    Sub-objective 2.2.

    Characterize population dynamics in response to the addition of treated BSAAO during leafy green growing season.

    Sub-objective 2.3.

    Evaluate enteric pathogen survival in dust containing BSAAO in lab setting to gain understanding of potential for aerial contamination from adjacent land use.

    For more information, click here.


    Objective Lead

    Dr. Manan Sharma, USDA ARS

  • Objective 3 - Preharvest and Harvest Practices

    Evaluate the risk of current on-farm preharvest and harvest practices for potential contamination of specialty crops with microbiological hazards.

    The preharvest environment is one of the earliest steps in crop production where contamination by foodborne pathogens can occur and even low levels can be amplified downstream along the production chain. Agricultural inputs, proximity to environmental reservoirs, production practices, urban run-off, human traffic, and animal intrusion, all can contribute to increased risk of pathogens on produce crops.

    These factors pose complex challenges in control and mitigation, and data are lacking in areas where 1) persistence and routes of contamination for protozoa and viruses may exist in soil and vegetative matter, including in piles of culled plant material; 2) recommendations and metrics conflict for some crops, e.g. dropped tomatoes are not harvestable, but melons and cucumbers grown on the ground are harvestable; and 3) interventions may have substantial impacts, e.g., implementation of co-management practices minimizing food safety risks associated with animal intrusion while maintaining ecological diversity of the agricultural environment. Routes of parasitic contamination and subsequent inactivation on crops that must be discarded or composted, remain understudied; with even less known about preharvest viral pathogen transfer in produce.

    Sub-Objective 3.1.

    Evaluate the persistence of non-bacterial food- and waterborne pathogens (parasites and viruses) on crops, in soil and in decaying vegetative matter and investigate possible routes of contamination through migration of particulate matter or direct contact of contaminated material.

    Sub-Objective 3.2.

    Identify risks and assess current recommendations for produce growing in contact with the ground (melons, cucumbers), dropping to the ground during cultivation (tomatoes, peppers) or placed onto the ground after harvest but before packing.

    Sub-Objective 3.3.

    Assess the inputs of fecal contamination and risks of contamination associated with pathogens from animal sources in produce fields, as well as survival and transfer to crops.

    For more information, click here.


    Objective Lead

    Dr. Kali Kniel, University of Delaware

  • Objective 4 - Postharvest Handling and Sanitation

    Determine the harborage, sources and patterns of contamination, and mitigation strategies for specialty crop contact surfaces (including recirculated water) in packinghouses to quantify risks.

    Postharvest handling issues have been repeatedly linked to cross-contamination during produce packing. Cross-contamination from postharvest washing and food contact surfaces to produce pose the greatest risks. Previous research and published risk assessments have established the risk of cross-contamination in water immersion systems, including dump tanks, if antimicrobial concentration is not maintained. The importance of antimicrobials is understood, but data are lacking for minimum concentrations required to mitigate the risk of cross-contamination. EPA labels exist for postharvest antimicrobials commonly used in dump tanks and flumes, but they have not been established for control of organisms of public health significance. There are also few scientific studies documenting the efficacy of commonly utilized antimicrobials (e.g., chlorine, peroxyacetic acid) at the concentrations routinely employed by industry.

    Further, packinghouse operations are concurrently experiencing increased scrutiny as cross-contamination during postharvest handling has been linked to multiple outbreaks, highlighting the importance of sanitary packing. Growers are also facing increasing scrutiny tied to management of harvest equipment and data is lacking to the risk of cross-contamination to produce from these surfaces.

    This work fills gaps in knowledge regarding management of postharvest risks tied to 1) minimum concentrations of sanitizers commonly utilized in postharvest washing to prevent cross-contamination of bacterial and viral foodborne pathogens and 2) effective sanitation strategies for preventing harborage of transient bacterial contaminants on food contact surfaces.

    Sub-objective 4.1.

    Determine efficacy of postharvest sanitizers used in dump tank or flume systems for bacterial and viral foodborne pathogens, considering industry use and management practices.

    Sub-objective 4.2.

    Determine critical parameters for effective sanitation of food contact surfaces most commonly associated with prevalence of foodborne pathogens and their indicators or where knowledge gaps exist.

    For more information, click here.


    Objective Lead

    Dr. Faith Critzer, University of Georgia

  • Objective 5 - Risk Modeling

    Create quantitative farm-to-fork risk assessment models of pathogens on produce.


    Risk assessment modeling has been shown to be particularly useful for integrating large bodies of experimental data to produce consistent and quantified estimates of the relative importance of different sources of contamination and food handling processes on final product safety. We will develop a generic risk assessment modeling framework to integrate the effectiveness of interventions identified in objectives 1-4. Preliminary data will be obtained from the published literature and supplemented as needed by expert opinion. Data from objectives 1-4 will be incorporated into the quantitative microbial risk assessment models as they become available.


    Development of literature and expert based models will be based on the Modular Process Risk Modeling approach and will address relevant steps in the farm-to-fork continuum. Potential contamination sources include agricultural water (objective 1), biological soil amendments (objective 2), preharvest and harvest practices (objective 3) and packinghouse practices (objective 4). Each of these sources is subject to variability, and to potential management interventions. All contaminants are subject to inactivation, influenced by the time between contamination and harvest, and climatic factors. Hazard characterization will use single-hit dose-response models. Risk characterization will be based on recommendations by the Interagency MRA Guideline Workgroup. Preliminary estimates of critical model parameters will be developed in R using a package that implements a model for eliciting, combining and validating expert judgments.

    Findings from these preliminary models will be shared with all objectives to inform their ongoing research. These models will be useful and inform the general structure and nature of the final models which will integrate project data.

    We will communicate with objective 1-4 investigators as we develop the literature and expert based models. We will provide guidance regarding results of our preliminary models and will receive guidance from them regarding findings from their research. This information will be used to develop @RISK models which integrate findings from ongoing research. New models will further be shared with the economic modeling and extension teams.

    Final working models that integrate project data from objectives 1-4, will be shared with objective 6 and objective 7. This will provide useful information for their objectives, as well as providing the risk modeling team with feedback regarding the structure and function of user-friendly versions of our models, which are part of the ongoing extension efforts. The risk assessment and extension teams will work together to develop guidance documents giving recommended practices based on insights from the project. We will develop realistic case studies using the user-friendly Excel spreadsheets to support decision making by individual businesses, and work with the Extension team to develop accompanying training materials.


    The risk models will integrate existing literature data, expert opinion, and experimental data from objective 1-4 to produce quantitative estimates of the relative importance of different sources of contamination and interventions on the safety of the final products. Sensitivity analysis will identify data gaps and factors that drive risk and are candidates for policy interventions. The risk assessment and extension teams will develop science and risk-based guidance documents giving recommended practices for specialty crop and for using the models developed based on insights from the project. User-friendly spreadsheets, training materials and realistic case studies will support decision making by individual businesses.


    Objective Lead

    Dr. Don Schaffner, Rutgers University

  • Objective 6 - Economic Evaluation

    Develop models for the evaluation of economic costs and benefits associated with produce pathogen reduction strategies.

    The assessment of economic costs and benefits associated with potential interventions provides stakeholders with information needed for cost effective risk-based decision making. We develop models and estimates that can be used to compare intervention costs with resulting benefits for individual producers, industry groups and policymakers.

    Objective 6

    Sub-objective 6.1.

    Evaluate economic burdens for consumers made ill by contaminated produce.

    The economic burden of foodborne illness includes costs from medical care, lost productivity, death, and lost utility from pain and suffering (for both acute and long-term illness). For this objective we will: 1) determine number of foodborne illnesses by pathogen; 2) identify sequelae associated with targeted pathogens and estimate incidence rates; 3) chart probabilistic disease outcome trees; 4) determine the share of illnesses attributable to selected produce types; 5) assess costs for each outcome node; 6) derive cost of illness for pathogens; and 7) characterize uncertainty using simulation modeling and global sensitivity analysis.

    Sub-Objective 6.2.

    Quantify costs to industry from foodborne illness events.

    Costs to industry from foodborne illness events include confiscation and destruction of foods, clean-up efforts, lost reputation, and litigation costs. We will 1) build a database of outbreak and recall data implicating produce; 2) evaluate consumer response to identified outbreaks and recalls; and 3) estimate the effect of outbreaks and recalls on price and sales of produce. The results of these analyses can be used by firms to prioritize food safety mitigation efforts. Policymakers can use the results to design interventions that build on, rather than conflict with, market incentives (thereby improving regulatory compliance and reducing enforcement costs, while reducing foodborne illness).

    Sub-Objective 6.3.

    Characterize consumer risk-related behavior.

    Consumers have a dual role in the risk analysis framework: both affected by and potential controllers of risk. To fully understand the economic effects of food safety efforts and events, we will characterize consumer risk-related behavior. We will model consumer behavior and illustrate the interplay between health costs and risk mitigation efforts. A consumer survey, coupled with existing data, will be used to 1) evaluate consumer response to proposed interventions (e.g., risk perceptions and behavior) and information shocks (e.g., publicized outbreaks), 2) assess risk mitigation activities (food choice and handling) and their effects on diarrheal illness, and 3) fill data gaps, as needed.

    Objective 6.4.

    Evaluate intervention costs and benefits.

    Decisions about whether to take action to reduce food safety risks are also influenced by the costs of these efforts. We will produce benefit-cost analyses, cost-effectiveness analyses, and return on investment measures (for firms) for interventions, where possible, by assessing costs for representative firm types and production practices. We will also provide stakeholders with user-friendly empirical models for adaptation and use. Data will come from the risk assessment (obj. 5), surveys (obj. 6 and obj. 7), leads for project objectives that examine interventions, stakeholders, and the literature.


    Objective Lead

    Dr. Robert Scharff, The Ohio State University

  • Objective 7 - Extension and Education

    Extending knowledge and awareness of the study outcomes through a translational bridging and leadership role.

    Objective 7 will focus on three specific sub-objectives:
         1. Assess stakeholders’ food safety knowledge, skills, and attitudes
         2. Communicate findings to stakeholders
         3. Develop and revise food safety curricula

    Sub-objective 7.1.

    Develop and disseminate surveys to assess current practices, food safety knowledge, skills and attitudes to inform project objectives.

    Four surveys will be developed in collaboration with each of the research sub-objective teams on use of 1) preharvest water treatments, 2) biological soil amendments of animal origin, 3) postharvest sanitizers, and 4) environmental monitoring programs. Survey questions will assess participants food safety knowledge, skills, motivations, and attitudes. Survey data will be collected with a focus on informing extension activities. The same surveys will be redistributed in year 4 and 5 to assess project impact.

    Findings will be incorporated into all facets of the research projects to inform research objectives and assist the extension group in identifying knowledge gaps. Surveys will be disseminated in-person and online. Results will be shared with the team to direct the development of resources. The results from each survey will be published in the peer-reviewed literature to inform future work; and survey results will be communicated in activities (both in-person and online) performed in subsequent sub-objectives.

    Sub-objective 7.2.

    Communicate project findings to key stakeholders and the public through traditional face-to-face engagement and other dissemination methods. The extension team will translate a subset of resources into Spanish based on stakeholder need.

    Methods of communication may include but are not limited to:

      • Local, regional, and national presentations at produce industry meetings to report on results from the research activities.
      • Traditional extension workshops including hands-on activities and targeting diverse audiences from growers to others in the food chain impacting the decisions of growers and packers.
      • Development of guidance documents for each survey topic.
      • Educational content packaged as stand-alone webinars, or series.
      • Podcasts, factsheets, demonstration videos, a twitter account and YouTube channel to engage stakeholders.
      • A project website including information on the project and objectives, contact information, frequently asked questions, links to social media platforms used by the project teams, and a calendar of upcoming outreach events.

    Sub-objective 7.3.

    Develop new and revise existing curricula to educate stakeholders at the local, regional, and national scope using both traditional in-person and self-paced online forums.

    New and revised curricula will be disseminated through in-person and self-paced online learning. Several project collaborators have developed regional food safety curricula that will be revised and expanded in collaboration with the researchers. Examples include a risk assessment curriculum which incorporates results from the modeling activities, an economics curriculum to help stakeholders prioritize capital investments to reduce risk and maximize return on investment and/or a curriculum on developing and using environmental monitoring programs to make changes that reduce risk. These new and revised curricula will include science-based recommendations from this project.
    Self-paced online learning platforms will be utilized to develop stand-alone and series modules on produce safety topics from basic to advanced. These modules will expand on the topics covered during the webinars.


    Objective Lead

    Dr. Laura Strawn, Virginia Tech

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