For more than a decade, romaine lettuce and other green leafy vegetables have been the source of E coli O157:H7 outbreaks (see Today’s Dietitian’s 2007 article “The E. coli Outbreak — Lettuce Learn a Lesson”). The most recent incident, which began in September 2019, was considered to be under control as of January 15, 2020, by the Centers for Disease Control and Prevention (CDC) and FDA; the final count of reported cases was 167 in the United States.
In 2013, a scientific investigation of a decade’s worth of data on hospitalizations and deaths attributed to food commodities (including seafood, farm animals, and plants) revealed that, among 17 commodities, the most illnesses were associated with leafy vegetables (2.2 million, or 22%). Illnesses associated with leafy vegetables were the second most frequent cause of hospitalizations (14%) and the fifth most frequent cause of death (6%). Since then, leafy vegetables have been estimated to have surpassed other food products in contamination rates. A 2020 article by venerated Boston Globe Spotlight Fellow Christine Haughney provided an in-depth view of the issue. In it, Haughney acknowledges that, while the FDA and CDC performed an investigation in the affected states, little has been done to change farming practices or mitigate future outbreaks.
Addressing the Issue Indoors
Controlled environment agriculture (CEA), also known as indoor or vertical farming, is growing—especially in the green leafy vegetable industry. Part of its value, on top of sustainability and freshness, is that plants are better protected from the outside world. Depending on the type of enclosure, CEA can avoid contaminations and infestations altogether.
But first, are all CEA companies the same? CEA farms can differ. Here are some examples of how each CEA farm can be unique:
- Vertical farms: Vertical means that the crops grow up, not out. This can include racks or a novel growing system.
- Open or closed: Some CEA farms are like “warehouses” of crops—indoors, but not enclosed and segregated. Some are fully enclosed with individual “grow units.”
- Environment: Farms vary in temperature, air flow, filtering system, humidity, carbon dioxide level in the air, and lighting. All of these factors impact plant metabolism and exposure to contaminants.
- Water and nutrition: The plumbing, water support, and nutrition delivery systems may be different; the water may be sourced from the tap, outdoors, or in our case, a purified water system. The nutrient composition delivered to the plants also can be proprietary.
- Pest control: The type of building where the crops are housed—indoor but not sealed, open to the air or outside—may affect whether pesticides, herbicides, or fungicides are used. Most CEA operations use no chemicals, as their outdoor exposure is minimal.
- Technology: Crops may be digitally tracked or automated to collect data and perform real-time monitoring via sensors to optimize growing conditions.
Indoor farms have the ability to control more of the environment and protect their plants from contamination. The following are ways indoor farms can mitigate outbreaks:
1. Enclose the crops. The more enclosed and controlled, the safer the plants will be. Farms that are 100% enclosed with double-door entryways and safeguards such as gloves, lab wear, and shoe coverings can reduce cross-contamination.
2. Segregate crops. Unlike growing in an open warehouse where pathogens can spread easily, grow units can be segregated and function separately from each other. This produces a more reliable product, but more importantly, can block the spread of bacteria and harmful viruses. Grow units can have their own air and water system so there’s little risk of cross-contamination.
3. Improve water and air quality. In any environment, plants take up elements, metals, chemicals, and even pollutants from water. To eliminate this risk, farms may purify the water and filter the air. This purification process can remove contaminants, including ions, heavy metals (such as mercury and arsenic), bacteria, protozoa, and viruses.
How Can RDs Help Consumers?
We want consumers to trust their food—especially produce. RDs can help them feel confident about their food.
To start, RDs can stay on the cutting edge of outbreak investigations. Visit the CDC and FDA sites. Read the reports and track the source. Provide consumers with the CDC’s fruit and vegetable food safety steps. Food safety also is top of mind for consumers during the COVID-19 pandemic, with many concerned about the virus spreading through the food supply chain. North Carolina State University Extension offers a bevy of resources in several languages concerning COVID-19 and food safety.
RDs also can suggest clients explore (when it’s safe to do so) indoor farmed produce in their local supermarket or area. Local hydroponic, CEA farms are popping up all over.
— Jenna A. Bell, PhD, RD, works in CEA and lives with her family in St. Petersburg, Florida.