CONTAMINATION PROBLEM
Growers contend with how to make sure leafy greens are safe
The Salinas Valley has long billed itself as the Salad Bowl of the World. Last year alone, Monterey County grew $1.4 billion worth of lettuce.
But for years the leafy green industry and Salinas Valley, which grows the majority of the nation’s lettuce, have also increasingly been known for something else: dangerous contamination in its leafy greens — particularly romaine lettuce — and an apparent inability to solve the problem.
The recurring contamination has sparked distrust in international markets, leading to a bombshell announcement in October that Canada effectively banned the importation of Salinas Valley- grown romaine lettuce until Dec. 31. The restrictions apply to romaine grown in four counties: Monterey, Santa Cruz, San Benito and Santa Clara.
Although the U. S. Food and Drug Administration had announced a sweeping plan in March aimed at reducing outbreaks related to leafy greens, Canada wasn’t willing to take the risk, the country’s food inspection agency said.
The move was a stark reminder to local growers who have been working vigorously
for more than a decade to safeguard leafy greens from contamination — a journey that in many ways has been an exercise in frustration.
“We absolutely recognize that there are millions of servings of these products consumed every single day. And the food is safe — except when it isn’t,” said Trevor Suslow, a food safety expert at UC Davis who recently stepped down as the vice president of produce safety at the Produce Marketing Association.
Any level of illness caused by leafy greens, Suslow said, is not acceptable.
Salinas Valley’s contamination problem drew international attention in 2006 when three people died and more than 200 people across the U.S. and in Canada were sickened from eating raw spinach contaminated with E. coli O157:H7, a virulent strain of bacteria that can cause severe stomach pain, bloody diarrhea and kidney failure.
Even though the source of the outbreak was eventually traced to a remote valley in San Benito County, where a cattle ranch owner had leased land to a spinach grower, the eyes of the world were suddenly on the Salinas Valley.
Federal investigators could not say definitively
how the spinach became contaminated. But they did find the outbreak strain in nearby cattle and wild pigs, theorizing the pigs had traipsed through the spinach field or bacteria from the animals’ feces had made its way into wells used to irrigate spinach.
And the outbreaks didn’t stop there. According to a recent study by several U.S. and Canadian government agencies, there were 32 E. coli O157:H7 outbreaks in the U.S. and Canada linked to leafy greens from 2009 to 2018.
In the fall of 2019 alone, three major outbreaks of E. coli O157:H7 were traced back to romaine lettuce grown in the Salinas Valley. All told, 188 people across the U. S. and Canada got sick from those outbreaks, leading to 92 hospitalizations and 16 cases of hemolytic uremic syndrome, a potentially fatal condition caused by bacterial toxins damaging blood vessels in the kidneys.
Romaine lettuce and other leafy greens are particularly susceptible to contamination. The crops are grown directly in the ground, sometimes putting it into direct contact with animal feces containing E. coli. And romaine’s large, open leaves can catch potential contaminants spread by air and water. Most importantly: Because romaine lettuce is eaten raw, there is no “kill step”— an opportunity to destroy pathogens through cooking.
Canada’s announcement took many in the industry by surprise, in part because there have been no outbreaks traced to the valley this year, said Norm Groot, executive director of the Monterey County Farm Bureau.
To some scientists, however, the Canadians’ decision seemed like a nobrainer.
“What took them such a long time?” said microbiologist Mansour Samadpour, president of IEH Laboratories and Consulting Group in Seattle.
Years ago, Samadpour was hired by San Juan Bautista-based Natural Selection Foods — which had packaged the tainted spinach that triggered the 2006 crisis — to overhaul microbial testing procedures.
Despite numerous investigations, no one has been able to find the exact source of contamination in last year’s outbreaks.
As was the case in the 2006 outbreak, fecal contamination from nearby pastures is suspected, according to an investigative report by the FDA on the 2019 outbreaks released last May. Investigators found a strain of E. coli O157:H7 that matched one of the outbreak strains at a cattle grate less than two miles upslope from a lettuce farm tied to the contamination.
Federal investigators said irrigation water was another suspect, as were env ironment a l fa c t ors such as heat, humidity, wind and wildlife, making the source of the outbreaks a moving target.
T he F DA recently launched a multi-year study aimed at determining how
human pathogens persist in the environment and contaminate produce.
But growers need answers now.
“How do we move forward with practices and implement something that works when we don’t have that full understanding?” Groot asked.
UC Davis’ Suslow said the food-safety system doesn’t need to be overhauled. “I think there are ways to more effectively and strategically apply what we do know, while we’re waiting to work out some of the things we don’t,” he said.
One organization committed to improving the safety of leafy greens is California’s Leafy Greens Marketing Agreement. The LGMA was created by farmers in response to the 2006 E. coli outbreaks.
Membership in t he LGMA is voluntary and allows growers to agree to a layer of food-safety regulations that exceed government requirements.
To reduce the risk of contamination from neighboring livestock farms, the LGMA last spring stepped up its efforts to scrutinize adjacent land use and has extended the required distance of buffer zones — land where no grazing is allowed and no leafy greens can be grown.
But Samadpour said that while the larger buffer zones might curb direct produce contamination from livestock, they won’t stop birds and other wildlife that routinely travel long distances from spreading contamination between pastures and row crops.
To combat pathogens in irrigation water, the LGMA in 2019 approved more stringent standards for testing and treating water used to irrigate leafy greens. The new standards include treating within 21 days before harvesting all water from open sources like canals and rivers that will be used in overhead irrigation.
“This is a pretty staunch
new metric — something that’s never been done in fresh produce before,” Greg Komar, LGMA’s technical director, said at a Sept. 1 webinar outlining the new standards.
Samadpour, however, said that just testing for generic E. coli won’t do much to catch O157:H7. He said that many common tests detect E. coli by observing a chemical reaction caused by a bacterial enzyme. But many strains of O157:H7, he said, don’t cause this chemical reaction, allowing dangerous strains of E. coli to slip by undetected.
“The problem is that nobody’s found the needle in the haystack,” said Steve Church, CEO of Church Brothers Farms in Salinas.
But Samadpour thinks there is a way to find the needle.
“We make the haystack smaller,” he said. “And we make our needle larger.”
Growers, he said, can shrink the “haystack” by testing smaller plots of land — say a quarter of an acre rather than 10 acres. And the “needle” can be enlarged by taking dozens of sample leaves instead of just one and testing them together, increasing the likelihood that the test will pick up evidence of contamination, Samadpour said.
Bill Marler, a Seattle attorney who has represented thousands of food poisoning victims, said Salinas Valley growers need more government reg ulation to “save them from themselves.”
“They may not like regu
lation,” but neither did the beef industry in the early 1990s, Marler said.
In 1993, an outbreak of E. coli O157:H7 in Jack in the Box hamburgers sickened more than 700 people and killed four children. The tragedy led to immediate changes in how beef was regulated, including a federal mandate that burgers must be cooked to an internal temperature of 155°F.
In addition, E. coli O157:H7 was classified as an “adulterant” in ground beef. That meant that any beef containing the bacterial strain could not be sold.
“They got their act together and, in fact, they put me out of business,” Marler quipped.
Groot, however, argued that the LGMA has actually been outpacing the FDA when it comes to raising standards for safely growing and processing leafy greens. The U.S. Food Safety Modernization Act of 2012, he noted, incorporated food safety standards originally established by the LGMA.
“The industry is a lot more nimble and can adapt itself a whole lot quicker,” Groot said.
Suslow points to a growing body of research on leafy greens contamination by various research groups. But, he said, there needs to be a system for sharing data on a large scale so that growers, scientists and government officials can learn from each other.
“No single grower or single commodity or industry,” he said, “is going to be able to fix this alone.”