For the ninth time since 1995, California’s Salinas Valley — the “nation’s salad bowl” — has been implicated in an E. coli scare involving salad greens.

Avoid E. coli, buy L. coli.

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As I write this, no definitive explanation has emerged for the latest outbreak, this one involving pre-washed, bagged spinach. But while the feds haven’t yet figured out how the spinach supply became tainted, they have pointed to a specific company: Natural Selection Foods, the nation’s largest pre-bagged spinach distributor, which runs a major processing plant in San Juan Bautista, near Salinas Valley. The company sells spinach under the Earthbound Farm label — a ubiquitous organic brand — as well as 33 others.

The role of organic spinach in the scare remains unclear. On Monday, Earthbound Farm posted a press release on its website claiming that “no organic products, including Earthbound Farm brand spinach or other products, have been linked to this outbreak at this time” (emphasis in original). However, it continued, “This does not mean that organic products have been cleared.” Natural Selection’s media telephone number was busy all day Wednesday, and a call to its PR firm, Murphy O’Brien Public Relations, ended in a brisk “no comment.”

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In a Wednesday afternoon press conference, a Food and Drug Administration official stressed that organic spinach had “neither been ruled in or ruled out” as a possible culprit. The official also revealed that the only bag of spinach that has so far been definitively linked to E. coli was one bought in New Mexico under the brand name Dole Baby Spinach — a conventionally grown product. Natural Selection packs and distributes spinach for Dole.

Still, predictably, flacks for the ag-chemical industry are gearing up to blame organic agriculture for the disaster.

Over on the Gristmill blog, professional organic skeptic Alex Avery has been busily impugning organic ag in the comments section. The culprit for the E. coli outbreak, he suggests, is “manure-based fertilizer,” an input widely embraced by organic growers.

Avery’s glee will likely prove unfounded. If some organic spinach is found to be tainted, it won’t specifically indict organic agriculture, because conventional spinach has already been shown to be infected. This implies that something besides standard organic practice caused the contamination.

The Producers

The organic question distracts from the real story behind the outbreak: consolidation of production. The San Francisco Chronicle reports that California produces three-quarters of the spinach consumed in the United States — and of that, fully three-quarters comes from Monterey County, which encompasses Salinas Valley.

Natural Selection Foods buys, processes, and packs salad greens for such giants as Dole, Trader Joe’s, and Sysco, among others. The company’s Earthbound Farm brand boasts on its website that it produces “[m]ore than 7 out of 10 organic salads sold in grocery stores” in the U.S.

In 1999, Salinas-based Tanimura & Antle, the largest U.S. fresh-vegetable grower and shipper, with 40,000 acres under cultivation in the United States and Mexico, bought a 33 percent stake in Natural Selection/Earthbound.

Given Natural Selection’s scale, it’s no surprise that an outbreak in a small region of California’s central coast could repeatedly wreak havoc nationwide.

One possible culprit is tainted water, either through irrigation or washing in the processing plant. In a letter last year, an FDA official sounded an alarm about this problem, writing that “creeks and rivers in the Salinas watershed are contaminated periodically with E. coli.” The rolling hills alongside the Salinas River support “extensive cattle ranches,” according to the Watershed Institute [PDF] at California State University. Might manure from these operations be leaching into the watershed?

Other sorts of agricultural runoff certainly have, including nitrogen-based fertilizer, which is used heavily on conventional farms. The Watershed Institute reports that 38 percent of wells in the Salinas Valley have nitrate levels higher than human consumption standards.

While at this point it’s impossible to know if bad water explains the valley’s E. coli problem — and the FDA has remained clueless even after nine outbreaks in a decade — it seems likely that the problem is related to scale. With so much land in a given area devoted to producing the same thing, problems reverberate through the system.

It’s Not Easy Eating Greens

I can see why pre-washed salad greens have grown into a $4 billion industry since 1986, when Earthbound Farm first sorted out the technology for keeping them fresh. It’s undeniably tempting to pluck a sealed bag of uniform greens from the supermarket counter and dump it right into the salad bowl, ready for a lashing of pre-made salad dressing.

But in doing so, you’re making huge demands on the environment. Even assuming organic production, consider that California salad greens consumed on the East Coast must be trucked across the continent and kept cool at a constant 36 degrees Fahrenheit. “At least given the fuel burned to get it to my table,” Michael Pollan writes in The Omnivore’s Dilemma, “there’s little reason to think my Earthbound salad mix is any more sustainable than a conventional salad.”

Also, as someone who grows salad greens commercially on a micro-scale, I can state bluntly that pre-bagged greens from mega-farms have zero flavor compared to the mixes small growers are producing for their local markets. One factor may be freshness. The California greens currently under recall include packages with sell-by dates of Oct. 1. Most small-scale greens growers I know distribute their product directly to customers within a day or two of picking.

Finally, given the industry’s (and the federal government’s) inability to stop deadly E. coli outbreaks from within the nation’s industrial-salad capital, our obsession with convenience bears a significant health risk.

The wisest strategy for consumers might be to buy greens in season from a nearby grower whose practices you trust — or, if possible, to grow your own.