To Joy Waite-Cusic, water’s role in produce safety is a two-edged sword.

While water’s ability to dilute chemicals is often viewed as a help in dealing with hazardous spills, it can also move freely and carry bacteria and other contaminants, making it a key contributor to many foodborne illnesses, the Oregon State University researcher said.

“We point to water as the spreader of all contaminants,” Waite-Cusic said. “When we think about microbial contamination, we really think about it as a distributor.”

Water can do that in part because “a lot of our foodborne pathogens can cause illnesses at very low cell density,” she said. Their “infectious dose” is low.

The field of study is relatively new.

“I would say we’re 20 years, maybe, into really recognizing fresh produce as a major contributor to foodborne illness and foodborne outbreaks,” Waite-Cusic said. Farms previously had not been regulated much beyond best-practice requirements.

Researchers still have much to learn about “how foodborne pathogens move in these open environments,” she said. “There are a lot of inputs and climatic changes. It’s a very dynamic situation.”

Partly because every season brings changes and challenges, researchers want to hear from producers frequently “so that our research remains relevant and accurate to industry practices,” Waite-Cusic said.

Romaine lettuce and onions each carry risk but challenge producers and researchers in different ways.

In lettuce, “we know water has been a pretty significant contributor in that system,” Waite-Cusic said. It’s a highly perishable crop with a short shelf life, little time between harvest and consumption, and scant opportunity to extend refrigerated storage or the time between final water application and harvest.

On the other hand, onions undergo field-curing, long periods of storage “and just limited water post harvest, so there is not a lot of opportunity for bacteria to spread,” she said.

In one experiment, Waite-Cusic and her colleagues introduced generic E. coli bacteria into water used to irrigate onions. Contamination occurred at a higher rate when overhead irrigation was used and at a lower rate when drip irrigation was used. But after the 28-day curing period following harvest, none was detected on bulbs. The team plans to investigate if the E. coli die-off is consistent in different seasons and locations.

A new study involves the risk of cross-contamination in post-harvest onion handling. It deals with the movement of salmonella or E. coli between two surfaces — such as from the onion to a surface such as wood, rubber or plastic — and the transfer of the bacteria to another onion. Researchers will also evaluate dry sanitizers.

Findings may provide evidence to support limiting future recalls instead of expanding them, she said.

A project funded by USDA looks at how well cleaning and sanitizing procedures work. Researchers tested bacterial levels and organic loads on food contact surfaces before and after they were sanitized. They surveyed fresh mixed vegetable, blueberry and onion facilities about their practices.

Current lab testing aims to show how sanitization procedures work on pathogens, particularly listeria and salmonella, Waite-Cusic said.

Title: Associate professor of food safety systems, Oregon State University, where she has worked for 10 years

Previous work: private laboratory work; commissioner’s fellow, U.S. Food and Drug Administration; post-doctoral researcher, The Ohio State University.

Education: B.S., food science, Oregon State, 2002; M.S., microbiology, Oregon State, 2004, Ph.D., food science, Ohio State, 2007.

Hometown: Florence, Ore.

Residence: Corvallis, Ore.

Family: Husband Joe Cusic, two sons

Hobbies: Gardening, home food preservation, making bacon

Affiliations: Oregon farm food safety team, International Association for Food Protection, Produce Safety Alliance lead trainer.