ALEX CHADWICK, host:
This is DAY TO DAY. Nobody knows for sure how deadly bacteria got into Salinas Valley spinach last month. But FDA investigators say they have found the genetic match to that strain of E. coli in some cow manure a half mile away from the spinach fields. Officials are quick to note this is not the smoking cow, so to speak.
But as John Sepulvado of member station KAZU reports, it does raise a big question for Salinas Valley growers.
JOHN SEPULVADO: What to do about those cows? They're practically everywhere on the hillsides in the Salinas Valley - grazing, chewing, mooing, and yes, pooping. Down below in the Valley, leafy greens carpet acres of land. One of the few fields not boxed in by cow-covered hillsides is here, where company Ocean Mist grows spinach.
Vice President of Operations Joe Pezzini says the company hasn't had one case of foodborne illness.
Mr. JOE PEZZINI (Ocean Mist): Because of our diligence in food safety, producing a crop in a very sanitary way, those are the insurances that we have to give our customers.
SEPULVADO: Pezzini says his company conducts water tests, soil samples, all the right things to keep his products safe. But Pezzini - like many in the agricultural industry - doesn't immediately point the finger at the cows, or in this case the lack of them, as a factor in producing unsafe leafy greens.
Mr. BILL MARLER (Attorney): It's human nature to ignore problems until they become so overwhelming that you actually do something about them.
SEPULVADO: That's lawyer Bill Marler. He specializes in foodborne illness cases, and he's suing the companies involved in the recent E. coli outbreak linked to spinach. And while government investigators say the cow manure hasn't yet been proven as the cause of the outbreak, Marler says it's good enough for court.
Mr. MARLER: Scientists are looking for near 100 percent certainty. Lawyers look at it just a little bit more than 50 percent. So certainly from my perspective it is the smoking cow pie.
SEPULVADO: There is some science suggesting E. coli tainted run-off can produce major outbreaks like the recent one in spinach. Michigan State University graduate researcher Bill Underwood is pioneering new E. coli research and he says many studies suggest water, through irrigation or run-off down manure-saturated hillsides like some above Salinas Valley, is often the culprit for contamination.
Mr. BILL UNDERWOOD (Michigan State University): So that the E. coli really aren't just naturally sitting around on the surface of plant leaves, but they're accidentally introduced onto the crop.
SEPULVADO: But again, government officials investigating the outbreak stress the cause has not yet been found. Dr. Keith Reilly(ph) with the California Department of Health Services adds that not all of the farms still under investigation have cattle around their perimeter.
Dr. KEITH REILLY (California Department of Health Services): This particular first ranch we talked about does have that, but not all of them share that commonality.
SEPULVADO: After previous E. coli outbreaks, some agricultural companies here resisted calls for tougher voluntary clean water guidelines. But it's different now. After a week long nationwide ban on spinach, local offices searched by the FBI, the industry is still facing an ongoing Mexican ban on lettuce imports from California.
Back in the field, Joe Pezzini notes the bad publicity and the threat of lawsuits has gotten the attention of the industry.
Mr. PEZZINI: We have to ensure that we continue to persevere in food safety and in always looking for better ways to do things.
SEPULVADO: But it might not be that easy. Because if it is cattle that's caused this last outbreak, what will farmers do? The hills here have always been for grazing, the fields have always been for growing, and the rain only runs downhill. For NPR News, I'm John Sepulvado in Monterey.