A field worker has unwashed hands. An animal squeezes through a small tear in a fence. Manure from a nearby hog farm trickles into an irrigation system.
Small mistakes like these are often difficult to identify as the sources of food-borne illnesses, a situation that has frustrated health authorities for years. The Food and Drug Administration and other agencies gather information about a contamination outbreak after people have already been sickened, and their investigations into what went wrong come well after the crucial evidence is gone.
Few rules are on the books that require preventive steps to make many foods — produce in particular — safer. The FDA now hopes to change that through sweeping rules designed to more closely track how growers, packers, shippers, distributors and retailers handle the produce Americans eat as it courses from the farm to consumer's tables.
Coupled with legislation that would give the FDA more enforcement power across the board, the changes could be some of the most significant improvements to the food safety system in decades.
"It's important to do this preventive work to keep people from getting sick, but also to maintain consumer confidence in the safety of fresh produce so people will make it a part of their diet," says Michael Taylor, the FDA's deputy commissioner for foods.
Taylor says the rules aren't written yet, but there are four areas upon which they will focus: water quality; employee hygiene; soil, including manure and compost; and wildlife intrusions on produce fields. Because potentially deadly bacteria like E. coli and salmonella come from human or animal feces, keeping excrement or traces of it away from growing foods is the primary objective.
The recent outbreak of E. coli in lettuce, which is thought to have sickened 30 people or more, is just one example of the difficulties in tracing a foodborne outbreak. The FDA still hasn't publicly identified what caused it.
Other outbreaks have been far worse. A 2006 outbreak of E. coli in fresh spinach killed three people and sickened 200. The FDA was not able to confirm the source of the outbreak but said it could have been wild pigs defecating in the area or contaminated water.
That outbreak cost spinach growers tens of millions of dollars and prompted industry to approach the FDA about stepping up federal guidelines on food safety.
"The impact (the spinach outbreak) had on industry was kind of a tipping point I think on a lot of levels," said Robert Guenther, a vice president of the United Fresh Produce Association, which represents the country's largest produce companies. He said the produce industry became frustrated with the FDA complaining that they weren't doing enough.
"I think there was a frustration level — 'OK, you tell us what you think the rules should be,'" he said. "We told them at that point to do it. Don't sit here and armchair quarterback."
Most produce growers and companies have strictly abided by voluntary and state guidelines for years, as safe food is good for business. But stricter federal guidelines could help catch less scrupulous growers and give the rest of the industry more consistent regulations to follow.
Taylor said the industry's support, increasing interest in Congress and the Obama administration's focus on food safety — a massive outbreak of salmonella in peanuts made headlines in Obama's first months in office — have all prompted the FDA to act. Another factor is the increase in known outbreaks over the last 20 years as detection has improved and consumption of fruits and vegetables has grown.
In an effort to allay some concerns farmers will inevitably have with the new rules, Taylor and his advisers have traveled around the country in recent months conducting listening sessions in 13 states. At a forum in Harrisburg, Pa., in early May, farmers agreed that something needed to be done but warned against punitive rules that could hurt business. Many of them said they were already taking extreme steps to make sure their food was safe.
Taylor says the agency will use feedback from the sessions in writing the rules, which will likely be broad guidelines focused on the riskiest foods. Those could be leafy greens, tomatoes, melons or other foods that have historically been the source of many outbreaks.
The new rules would be directed by legislation moving through Congress that would give the FDA stronger oversight of food safety, including new authority to order recalls and a system for better tracing the source of foodborne illnesses. The guidelines would also follow the recommendations of an Institute of Medicine report released this week that said the FDA needs to reorganize to better focus on the riskiest foods.
Food safety advocates say they hope the rules include more checks along the way as food travels from field to mouth.
"There needs to be a system that can both track that food and also give us some assurance that it is being properly processed and handled along that journey," said Erik Olson, director of food and consumer product safety at the Pew Health Group. "Any weak link in the chain can cause a problem."