Elizabeth Weise, USA TODAY

Kroger , the nation's largest supermarket chain, has announced it will stop selling sprouts on Monday because of their "potential food safety risk." It joins retail behemoth Walmart, which quietly stopped selling the crunchy greens in 2010.

"After a thorough, science-based review, we have decided to voluntarily discontinue selling fresh sprouts," Payton Pruett, Kroger's vice president of food safety, said in a statement.

"This is big," said Marion Nestle, a professor of food safety at New York University. "This is a major retailer saying 'We aren't going to take it anymore. We can't risk harming our customers, and our suppliers are unwilling or unable to produce safe sprouts.' "

The industry's trade group expressed concern but said it was working to keep its products safe.

"We hope that the Kroger decision doesn't have a domino effect," said Bob Sanderson, president of the International Sprout Growers Association. The industry, which depends on sampling and testing to insure sprouts are not contaminated with pathogens, is working with the Food and Drug Administration and other groups to create better safety protocols.

"We're trying, but it's very challenging," Sanderson said. "These organisms can be anywhere." The industry is also working towards a "sprout-specific" food safety audit for producers.

Walmart stopped selling sprouts two years ago, in October 2010, said spokesman Kory Lundberg.

"It really comes down to our commitment to our customers' safety and knowing the microbial risk associated with sprouts," he said. However, he added the company continues to work with the sprout growing industry to create "enhanced food safety controls and microbial intervention strategies that would result in safer sprouts."

Between 1990 and 2010, more than 2,500 Americans were sickened by contaminated sprouts in at least 46 outbreaks, according to data from the Centers for Disease Control and Prevention. Salmonella was identified in 37 of the 46 outbreaks, E. coli with eight and listeria with one.

"It's great news," said Caroline Smith DeWaal, food safety director with the Center for Science in the Public Interest in Washington. Simply because of the way sprouts are grown they're "unavoidably unsafe," she said.

As the FDA says, "seeds and beans need warm, humid conditions to sprout and grow. These are the same conditions that are ideal for bacteria to grow, including dangerous bacteria like salmonella if they are present." The seeds used for sprouts can carry pathogens inside, where they're very hard to kill. Methods to destroy the contamination, such as irradiating the seeds or soaking them in bleach, haven't proved successful.

The Cincinnati-based supermarket chain operates 2,425 supermarkets in 31 states under names including Kroger, City Market, Dillons, Jay C, Food 4 Less, Fred Meyer, Fry's, King Soopers, QFC, Ralph's and Smith's.

Recent large sprout based outbreaks include:

-April 2012. Clover sprouts linked to infection with an E. coli variant in 29 people infected in 11 states.

-June 2011. Alfalfa sprouts contaminated with salmonella enteritidis sickened 21 people in five states, three of whom required hospitalization.

-May-June 2011. Fenugreek sprouts sickened more than 4,300 people and killed 50 in Europe, the United States and Canada.

-April-July 2011. Alfalfa sprouts and spicy sprout mix were linked to salmonella enteritidis that affected 25 people in five states.

-Nov. 2010-Feb. 2011. "Tiny greens" alfalfa sprouts and "spicy sprouts" sickened 140 people with salmonella in 26 states; 24(PERCENT) are hospitalized.

Mung bean sprouts have long been a component of Chinese cuisine, quickly stir fried as a vegetable. Alfalfa sprouts became popular in the 1970s in the United States as part of an overall trend towards fresh food and healthy eating. Broccoli sprouts became an overnight sensation in the 1990s when scientists at Johns Hopkins University found a cancer-fighting chemical in broccoli that was present in even higher concentrations in sprouts.

FDA and the Centers for Disease Control and Prevention advise that children, the elderly, pregnant women and people with weakened immune systems should avoid eating raw sprouts of all kinds, including alfalfa, clover, radish and mung bean sprouts. Sprouts can be "cooked thoroughly to reduce the risk of illness," the FDA says.