CA Longitudinal Study
CALS: Central Coast Study on Environmental Factors
FDA releases initial findings of 5-year CA Central Coast environmental study, highlighting benefits of government and industry collaboration
California Department of Food and Agriculture Statement on CALS
California’s agriculture industry continues to demonstrate that science and partnerships are the cornerstone of advancing food safety.
In April 2021, CDFA Secretary Karen Ross Called for industry participation to help solve recurring food safety incidents. This action followed a number of leafy green outbreaks between 2018 and 2020 that were traced back to the California Central Coast growing region and linked to a unique isolated strain of E. coli O157:H7. In response, the U.S. Food and Drug Administration (FDA) and Western Center for Food Safety at UC Davis launched a five-year California Longitudinal Study (CALS) in coordination with CDFA, highlighted as part of the FDA Leafy Greens STEC Action Plan. The CALS study aims to understand environmental factors that may pose risks to food safety in the growing environment.
On March 5, 2026, FDA released a constituent update (link to CU once it’s posted) reflecting progress and initial findings of this five-year research study. This is the largest, most comprehensive sampling study conducted in the Central Coast growing region to date. Outcomes of the research are consistent with historical scientific literature and offer insights that the current food safety regulations, metrics and practices are effective when implemented consistently and judiciously. Additionally, with this emerging body of environmental data, California agriculture will explore new, innovative ways to focus on prevention measures for continuous improvement of food safety.
“Produce safety is a shared commitment across the entire supply chain,” said CDFA Secretary Karen Ross. “The California Longitudinal Study is the result of our public and private sectors working together to advance science-based practices, improve transparency and reinforce consumer trust. It’s all part of California agriculture’s essential mission of feeding the United States and beyond safely, sustainably and reliably. Initial findings verify that the actions we’re taking in the Central Coast region to enhance food safety are moving us in the right direction, and we are committed to maintaining this focus.”
California’s produce industry continues to make significant strides through improvements in food safety risk education and on-farm practices, led by coordinated efforts among government, academic institutions and industry associations. Ongoing training, inspections and audits, data sharing and innovative technology help ensure that fresh fruits and vegetables reach consumers safely. Equally important are the ongoing partnerships forged through California Agricultural Neighbors (CAN), which began in 2021. CAN is a locally led, locally convened group that brings together diverse agricultural stakeholders across the Salinas Valley to explore and reinforce where food safety advancements, rooted in One Health principles, can be discussed, fostered and implemented. One Health is a collaborative, multidisciplinary, systems-thinking approach that recognizes the health of people is interconnected to the health of animals, plants, and our shared environments.
“As stewards of the land and the food system, members of CAN know the significant responsibility inherent with feeding a nation, and recognize that food safety and food security are fundamentally interconnected,” said Natalie Krout-Greenberg, director of CDFA’s Inspection Services Division and co-lead of CAN. “Stakeholders engaged in CAN remain committed to advancing produce safety through continued collaboration, shared learning, adaptive practices, and sustained collective commitment.”
FDA and Partners in the Central Coast Agricultural Region of California Share Findings from Multi-year Environmental Study
On March 5, 2026,, the U.S. Food and Drug Administration is sharing initial findings from a multi-year environmental study conducted in California’s Central Coast agricultural region that will inform efforts to further improve the safety of produce — an essential component of a healthy diet. The California Longitudinal Study was conducted in partnership with the Western Center for Food Safety at the University of California, Davis, the California Department of Food and Agriculture, and regional agricultural stakeholders.
The Central Coast of California is farmed year-round and supplies a large volume of produce, which includes more than 400 commodities. However, there have been periodic foodborne illness outbreaks associated with the region, including several that occurred between 2016 and 2020 caused by the same E. coli O157:H7 strain. This study sought to identify environmental factors that significantly contribute to the introduction, persistence, and spread of foodborne pathogens that could contaminate produce prior to harvest. Increasing our understanding of the ecology of this growing region as it pertains to foodborne pathogens is to the benefit of consumers, producers, academia, and food safety officials as it allows for continued improvement in best growing practices to enhance food safety.
The longitudinal study, which began in 2020, followed an adaptive research design in which sample collection matrices, sites, and frequencies were continually assessed and refined to obtain maximum useful, practical information. Through repeated sample collection, testing, measurement, and analysis, the research team observed trends in pathogen presence in this region over time, providing insightful information on prevalence, location, and potentially influencing factors such as seasonality, weather conditions, and domesticated and wild animal activities on adjacent and nearby land.
Initial findings related to E. coli O157:H7 and other Shiga toxin-producing Escherichia coli (STEC) have been posted to the FDA’s California Longitudinal Study webpage and are summarized below:
Animal Sources of Contamination: Fecal samples from rangeland beef cattle, feral pigs, deer, birds, and coyotes were frequent sources of STEC. Viable STEC was recovered from fresh and older, drier feces from livestock and wildlife found in the sampling area. These results suggest that STEC may remain viable in fecal material for extended periods.
Environmental Sources of Contamination: Surface waters and associated sediments may facilitate STEC persistence, and in the case of water, STEC movement in the region. STEC was not recovered in a substantial amount of soil or air samples, indicating that these are not likely impacting the spread of STEC in the region. However, STEC was observed in water and sediment from rivers and creeks, and to a lesser extent in irrigation tailwater and tailwater sediment (accumulations of field runoff from irrigation practices) collected at field edges.
STEC Diversity, Persistence, and Movement: Twelve different E. coli O157:H7 strains were isolated from environmental samples; however, the strain responsible for outbreaks between 2016 and 2020 was not recovered. STEC isolated from wildlife feces genetically matched strains from cattle feces, other wildlife feces, and in some cases, water, sediment, and soil. Six different highly pathogenic STEC serotypes were identified and some strains of these serotypes persisted for nearly two years.
The FDA will engage with stakeholders to further discuss the data and findings from this study and assist stakeholder efforts to develop practices to manage the risks posed by the potential sources of contamination. Additional information and publications will be added to FDA’s California Longitudinal Study webpage as they become available.
The FDA thanks its state, academic, and agricultural partners who contributed to this study.
