WASHINGTON – Federal food-safety regulators now will allow producers to irradiate spinach and iceberg lettuce to protect consumers from disease.

The Food and Drug Administration is set to give the green light Friday to a practice that officials have concluded is safe. The long-awaited decision comes in the wake of high-profile bacterial outbreaks involving tainted greens.

“FDA concludes that irradiation of iceberg lettuce and spinach conducted in accordance with good manufacturing practices will reduce or eliminate bacterial populations,” the agency says.

“I hope we will see a reduction in the number of food-borne illnesses,” Dr. Robert Brackett, chief scientist with the Grocery Manufacturers Association, said Thursday. “It gives the industry another tool to increase food safety.”

The FDA’s decision is spelled out in a 25-page document that will be published Friday in the Federal Register and that emphasizes the safety of food irradiation. “There is no reason to suspect a toxicological hazard due to consumption of an irradiated food,” the FDA says.

The decision adds leafy greens to the menu of foods that can be irradiated, including spices, dried vegetables and ground beef. In theory, the low doses of radiation will eradicate potentially devastating Escherichia coli bacteria as well as other nasties, including salmonella, shigella and listeria.

An estimated 70,000 U.S. residents fall ill annually because of the bacteria group commonly known as E. coli 0157, according to the Centers for Disease Control and Prevention. The severe stomach cramps, diarrhea and vomiting can prove particularly ruinous for young children and the elderly.

Two elderly women and a 2-year-old child died and more than 200 people in 26 states fell ill because of a late 2006 E. coli outbreak that ultimately was traced to packaged spinach grown on a central California farm. California growers subsequently formed the California Leafy Green Handler Marketing Board to oversee farm-safety standards.

The request to irradiate leafy greens, however, came from higher up in the food chain: the food processors, instead of the farmers.

The FDA’s decision comes nine years after what was then called the National Food Processors Association requested approval for the use of radiation. The trade organization’s 95-page petition filed in August 1999 asked for an “expedited” decision, covering multiple foods.

That didn’t happen, as the notion of bathing food with X-rays alarmed some consumer advocates. After the 2006 spinach episode, however, industry officials with what is now called the Grocery Manufacturers Association pressed for at least a quicker decision on leafy greens.

“The treatment of food with ionizing radiation can produce a wide variety of beneficial effects,” the trade association noted in its application. “However, it should be clear that irradiation is not a remedy for unsatisfactory production practices.”

One 1997 study that the trade association cited, for instance, found that irradiating fresh-cut, commercially prepared lettuce slashed the microbial population from 220,000 “colony forming units” per gram to barely 200 per gram. The colony-forming unit per gram is the standard measurement for microbial contamination.

Radiation also can whittle away at certain vitamins, including thiamine, vitamin E and vitamin A. The trade industry’s application nonetheless asserted that “it is unlikely that irradiation will have significant nutritional impact on a balanced diet of raw, canned and ready-to-eat fruits and vegetables.”

The FDA, in its decision statement to be published Friday, agreed that irradiation “will not have an adverse effect” on the nutritional makeup of spinach and iceberg lettuce.

“We don’t have much concern about the safety of irradiated foods,” said Caroline Smith DeWaal, the food safety director for the Center for Science in the Public Interest, a nutrition and food-safety advocacy group, “but there are simpler steps that can be taken.”

Smith DeWaal called irradiation a costly “end of the line technology” that should be accompanied by safer produce-handling measures at the farm level.

An estimated 680 million pounds of spinach were grown in the United States last year, with California accounting for about three-quarters of that. New Jersey and Arizona are the other two leading producers of spinach, which increasingly has been bagged and pre-packaged by companies such as Dole.