The bacterium that has sickened people across the nation and forced growers to destroy spinach crops is so pervasive in the Salinas Valley that virtually every waterway there violates national standards.
“There are many sources of water coming into the watershed, and I guarantee you that they all have generic E. coli,” and many carry the deadly E. coli strain linked to food poisonings, said Christopher Rose, an environmental scientist at the state’s Central Coast Regional Water Quality Control Board, which tests the region’s waterways.
Federal officials said Wednesday they are focusing on nine fields in San Benito, Santa Clara and Monterey counties as possible sources of the bacteria-contaminated spinach that killed one woman and sickened at least 145 others in 23 states.
Investigators also announced that spinach found in the refrigerator of a New Mexico resident who became ill tested positive for E. coli 0157:H7, the dangerous bacteria strain responsible for the outbreak. The finding confirmed suspicions that the tainted spinach originated from California’s Central Coast, where it was packaged by Natural Selection Foods under the Dole label.
Monterey County’s Salinas Valley is one of the world’s most intensely farmed regions and a major supplier of lettuce and spinach to the nation. The current outbreak of food poisoning marks the 20th time since 1995 that the dangerous E. coli strain has been linked to lettuce or spinach.
The source of the pathogen has not yet been pinpointed, but tainted water is considered a likely culprit.
Many creeks and streams near the region’s spinach fields, including the Salinas River, Gabilan Creek, Towne Creek, Tembladero Slough and Old Salinas River Estuary, are known to be carriers of the E. coli strain implicated in the food poisonings. When consumed, people experience cramping, diarrhea and, in severe cases, kidney failure.
Although the growers do not draw water from creeks to irrigate their fields, their crops could be tainted by runoff from nearby livestock operations or Central Coast urban areas.
“What is troublesome with this particular watershed is that it has low-lying land in agricultural production, and flooding certainly occurs in the lower portions. If we have high levels of E. coli in surface waters and they are flooded onto fields, that is certainly a potential source of contamination,” Rose said.
Only one waterway in the lower Salinas River watershed does not violate federal E. coli standards, and it is in a state park, surrounded by natural land. Some waterways are so contaminated they contain 12,000 or more organisms per 100 milliliters of water -- 30 times the Environmental Protection Agency’s standard. Ingesting just a few organisms can make a person sick.
E. coli is ubiquitous in the environment because it is found in the intestines of every species of warm-blooded animal. Wherever there is feces, whether bird, human, cow, or dog, there is E. coli. “The presence of E. coli in water is a strong indication of recent sewage or animal waste contamination,” said Dale Kemery, spokesman for the EPA’s Office of Water.
Packagers take great care to destroy bacteria on greens, washing lettuce or spinach in baths of water, chlorine and citric acid before spinning it dry and sealing it in plastic bags.
The O157:H7 strain was first recognized as a cause of illness during a 1982 outbreak traced to fast food hamburgers. But its prevalence in most regions is unknown because there is no EPA requirement to test for it in waterways, wells or irrigation water, Kemery said.
After food poisoning outbreaks several years ago, regional water officials stepped up sampling and added analysis for the deadly strain in the Salinas watershed, finding the bacteria in several waterways next to areas where livestock graze.
E. coli is a national problem, but it is especially severe in livestock areas. A single cow can shed as much as 100 billion fecal bacteria per day. The food-poisoning outbreak could pit vegetable growers against livestock owners, both economic powerhouses in the state.
Monterey County’s spinach fields are downstream of the Gabilan Mountains, where beef cattle, dairy cows and horses graze. En route to the Salinas River, many tributaries flow through the livestock areas, picking up bacteria. The water then flows through the low-lying valley where vegetables are grown.
Cattle and other livestock graze near the banks of the creeks, and their manure can easily contaminate the water with millions of E. coli organisms. “In some areas, grazing has resulted in manure lining the banks of channels of tributaries to the Salinas River,” a June report by the Central Coast water board stated.
How much of the region’s water contamination comes from cattle is unknown. “What is certain is that livestock are a source of E. coli, including E. coli O157:H7,” in several creeks that flow into the Salinas River, the board’s report concluded. It also found that “the most frequent occurrence of E. coli O157:H7 occurs at sites flanking areas used for grazing purposes.”
Complicating matters, urban areas are sources as well. Runoff flowing from streets in Monterey County also carries E. coli, largely from dogs, cats and other domestic or wild animals. In Salinas, storm water, measured in June, contained 14,550 E. coli organisms per milliliter, 36 times the EPA standard.
Water used for drinking supplies and irrigation is not threatened by the bacteria because it is drawn from deep wells, more than 100 feet below the surface, and bacteria is readily filtered by the region’s clay soil.
Consequently, Rose said the groundwater that Salinas Valley growers use to irrigate fields is probably not to blame for the outbreak. Owners of irrigation wells and private wells do not have to test for bacteria or comply with the EPA’s drinking water standards, but large Salinas Valley growers test their wells anyway, at the request of grocery chains concerned about food safety, he said.
“These outbreaks make it appear that the produce was contaminated before harvest. It’s a strong suspicion by everyone. So some of the things the investigators will look for is whether certain fields flooded and the quality of the irrigation water used, the location of farms near where animals may be grazing, and whether any wildlife may frequent certain farms,” said Robert Mandrell, leader of the produce-safety and microbiology unit at the USDA’s Agricultural Research Service in Albany, Calif.
State agricultural leaders say that if livestock are contaminating leafy green crops, they will work together because their aim is the same: Ensuring the safety of food produced in California, which has been the nation’s leading supplier for over half a century.
Statewide, several hundred ranchers have already installed fencing to keep grazing cattle away from waterways in a program begun a decade ago, said Matt Byrne, executive vice president of the California Cattlemen’s Assn.
“Truly we all have the same incentive to preserve the land and the water that is so critical to us in providing a safe food supply to people around the world,” Byrne said.
Other than water, another likely source of the tainted spinach is wild animals, particularly birds. Experts say migrating birds, which digest the bacteria in manure and then fly over the spinach fields leaving droppings, could be responsible for poisoning hundreds of people.
Rose completed this year’s water testing on Wednesday and now U.S. Department of Agriculture microbiologists are analyzing the data for clues to the origin of the outbreak -- which will take weeks.
“From my experience working with pathogen-related issues, it is seldom the case where you can find ‘the source.’ The sources are multiple. There are so many carriers of O157:H7 as well as generic E. coli that it’s hard to pin down,” Rose said.
Tracking the origin of this specific pathogen is difficult for several reasons. Water tests can only detect the presence of the bacteria, not its concentration. In addition, it can easily move around and disappear. Ingesting just a few organisms can make a person sick.
“You may find it in a sample, and then 30 seconds later you may not find it in a second sample from the exact same site,” Mandrell said.
The Clean Water Act requires all U.S. waterways to comply with bacteria standards. In addition, California has a “zero discharge” rule for livestock operations -- no runoff is allowed.
Both mandates, however, are difficult to enforce.
The water board is now developing new limits, called Total Maximum Daily Loads, in an effort to bring the Salinas River watershed into compliance with the federal law. That could mean costly new controls on the livestock industry as well as cities responsible for cleaning up runoff.
“Given the fact that we have elevated concentrations in this area, and given the fact that we now have this outbreak, it seems apparent we need more regulation” to clean up the region’s waterways, Rose said.