Tainted spinach raises big question of manure on food crops

Published 7:55 pm Tuesday, October 10, 2006


Ten years after one of the country’s top food safety experts warned of danger from putting manure on food crops, Americans are still being devastated by manure-born pathogens. It doesn’t have to be.

Contaminated raw spinach has just killed at least one person, brought devastating kidney failure to 23, hospitalized more than 75, and sickened more than 150 people across America. The deadly spinach has been traced back to Natural Selections Foods, the largest grower of organic lettuce and spinach in the United States.

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Organic rules bar the use of manufactured fertilizer on their crops, so organics use composted manure and other animal wastes on their fields. Animal manure is the ultimate source of the virulent E. coli O157:H7, which contaminated the spinach.

In 1995, the Journal of the American Medical Association quoted Dr. Robert Tauxe, head of foodborne illnesses for the U.S. Centers for Disease Control, telling a medical conference that “‘Organic’ means a food is grown in animal manure. . . . We got rid of human waste in our food and water, and I think we’re going to have better control in the future of manure in our food and water.”

The Organic Trade Association responded that organic food was safe because farmers compost their manure. Dr. Tauxe responded that “Unfortunately, knowledge of the critical times and temperatures needed to make composted animal manures microbiologically safe is incomplete.”

Today, USDA organic rules allow manure to be applied after just 3 days of composting — right up to harvest time! Raw manure can be applied until 90 to120 days prior to harvest, under most state-level rules for all farms. But a recent University of Minnesota study found that produce grown with manure aged 6 to 12 months was still 19 times more likely to be contaminated with E. coli than foods grown with manure aged more than a year.

Virtually no farmers age their manure for a year as too much of the vital nitrogen gasses off into the air during that time. Instead, most conventional farmers put their manure only on feed crops such as corn or on pasture. That may be why the Minnesota researchers found organic produce three times more likely to be contaminated with E. coli (7% of samples) than conventional (2%).

Organic activists love to claim that the deadly O157:H7 strain of E. coli is caused by “factory farming.” Not so. The USDA says it has found O157:H7 in every cattle herd it’s tested for it. A Swiss study last year found “no significant differences” in O157:H7 prevalence between organic and conventional dairy farms. Claims that “grain feeding” of cattle causes O157:H7 to flourish are also unsupported; various studies have found the opposite.

Washing the food can’t fully protect consumers either. Rutgers University has shown that lettuce (and likely spinach) can take up O157:H7 via its roots and harbor the pathogens inside the leaves! In short, there is no practical way to ensure full safety in the food crops fertilized with manure, composted or not.

Is it time to get the manure out of human food crops?

States could require that manure either be used on non-food crops or composted for at least a year. Annual questionnaires could identify the relatively few farms that compost with regular government inspections made.

This will raise howls of protest from the organic movement, which also protested the current weak manure rules. However, it’s now clear that using manure on food crops involves a serious public risk—especially with leafy produce like lettuce and spinach. The organic movement should want to ensure its customers health as urgently as do public health officials.

Eating no longer needs to be a deadly game of Russian roulette.

Dennis T. and Alex A. Avery,

Hudson Institute

(Dennis Avery is Director of Hudson’s Center for Global Food Issues, where Alex Avery is director of research and education. Alex’s new book, The Truth About Organic Foods, is due in October from Henderson Communications. Readers may write them at Center for Global Food Issues (www.cgfi.org), PO Box 202, Churchville, VA 24421)