(Dec. 10, 6:20 p.m.) The California Leafy Green Products Handler Marketing Agreement — and a similar arrangement in Arizona — mandates a no-harvest zone within a 5-foot radius of animal manure discovered in vegetable fields.

Months of research in Arizona back the standard for keeping food products safe from bacterial contamination.

“Our research concludes the standard provides a safe parameter, as long as the growers don’t irrigate when it is windy,” said Jorge Fonseca, vegetable and postharvest specialist at the University of Arizona-Yuma. “Other than that, it is a very conservative metric.”

Fonseca and his colleagues at the center have conducted a series of tests, funded in part by the California Leafy Greens Research Board, Sacramento, Calif.

Researchers placed fresh fecal matter from cattle, dogs and birds in three acres of romaine planted at the center’s field, he said.

“We used a generic E. coli, and inoculated the fecal matter,” Fonseca said.

“We found that several factors would affect the spread of the pathogens: wind speed, wind direction, where the fecal matter was placed and the maturity of the plants.”

It was the overhead sprinkling that researchers found caused the bacteria to be dispersed, he said. Where the water puddled in the field, the splashing created when the sprinklers delivered the irrigation water spread the E. coli, he said.

When the wind speed is less than 13 miles per hour, the spread of the fecal particles by the splashing is limited to 18 inches or less, Fonseca said. The age of the romaine also varied the spread.

“More mature plants help to create a barrier against the spread of the pathogens,” he said. “The splash of the irrigation water naturally travels farther when the plants are younger and shorter.”

Irrigating shortly before harvest also can amplify the spread of the bacteria, Fonseca said, because workers walking through a moist field that is contaminated could carry the pathogen to previously unaffected areas.

The final stage of the testing will run through January, Fonseca said. The goal of the final stage is to confirm the findings already gathered.

“We could do it by calculation, but it’s better to confirm our findings in the field,” he said.

In the final stage, researchers are varying the distance between the two pipelines on which the sprinklers are mounted to determine whether the splashing can be minimized, Fonseca said.

One factor yet to be tested, Fonseca said, is whether the higher humidity found in California’s coastal growing regions would increase the spread of the bacteria.

“We discussed humidity, but wind is viewed as more important now,” he said. “It’s definitely something to take into consideration if the findings are applied to California vegetable crops.”

Because there are so many variables, it is difficult to specify the effects pathogen contaminated produce can have on consumers, Fonseca said.

“It depends on how the bacteria attach to the vegetables and how much it grows between the field and the kitchen,” he said. “If the cold chain is broken and the temperature climbs to 50 degrees, there could be substantial growth of the pathogen.”

Home washing of vegetables with water or sanitizers can help,but will not eradicate the bacteria.

“It’s very unlikely that the pathogen would be completely removed at the kitchen level,” Fonseca said. “It could have a significant reduction, but it is never going to be completely removed with water or sanitizers.”

What could be an equally serious kitchen problem — or even greater — is the potential for cross contamination from meat products to salad vegetables, Fonseca said.

“As an industry, we need to educate consumers, because I suspect there are many health problems due not to agricultural practices but that originate in the kitchen,” he said. “Some meats contain high levels of pathogens, so the possibility of contaminating our salads in the kitchen is really high.”

Consumer education is necessary, Fonseca said, because illnesses caused by tainted food prepared in the home are rarely publicized.

“It’s not like the coverage that happens when the outbreaks are linked to food at a restaurant,” he said.