Environmentalists and health-conscious consumers are always voicing their worries about antibiotics in meat and milk. But now these folks have even more reason to be concerned: A new study shows that antibiotics can also show up in crops like corn, lettuce, potatoes and onions.

Unlike the European Union, which banned the use of antibiotics in animal feed in 2006, US farmers frequently feed their pigs, cattle, and chickens antibiotics in order to fend off infections and disease. When manure from these animals is used to fertilize plants, the crops themselves can absorb antibiotics excreted by livestock.

From Environmental Health News:

"Minnesota researchers planted corn, green onion, and cabbage in manure-treated soil in 2005 to evaluate the environmental impacts of feeding antibiotics to livestock. Six weeks later, the crops were analyzed and found to absorb chlortetracycline, a drug widely used to treat diseases in livestock. In another study in 2007, corn, lettuce and potato were planted in soil treated with liquid hog manure. They, too accumulated concentrations of an antibiotic, named Sulfamethazine, also commonly used in livestock.

As the amount of antibiotics in the soil increased, so too did the levels taken up by the corn, potatoes and other plants.

'Around 90 percent of these drugs that are administered to animals end up being excreted either as urine or manure,' said Holly Dolliver, a member of the Minnesota research team and now a professor of crop and soil sciences at the University of Wisconsin-River Falls. 'A vast majority of that manure is then used as an important input for 9.2 million hectares of (US) agricultural land.'"

Although the health implications from antibiotics in foods we eat haven’t been proven, officials worry that antibiotic-laced meats, veggies, and milk can create resistant strains of bacteria in food and the environment. Once resistant strains develop, it can reduce the effectiveness of human antibiotics. Some scientists also attribute antibiotics to the rise in rates of childhood allergies and asthma.

And if you think eating organic means you’ll avoid drug-laden foods, think again: Although antibiotics are banned from meat and milk that’s certified organic, manure isn’t regulated, so antibiotics could end up in organic crops, especially leafy greens and root vegetables.

This study highlights yet another flaw in the organic labeling system: It wasn’t until recently that the Department of Agriculture (USDA) closed a loophole in organic milk regulations and required farmers to put their cows out to pasture where they could eat fresh grass. Before that, many cows were indoors in large feedlots. And in November, the USDA cleared the way to label some farmed fish as organic, a move that angered environmentalists, who argued that the concept of farmed fish goes against the ideals of the organic movement.

These are all issues Tom Vilsack will face as he’s sworn in as head of the USDA. Whether or not Vilsack will beef up organic standards—and whether that’s even a part of his agenda—remains to be seen.

This article originally appeared in "Plenty" in January 2009.

Copyright Environ Press 2009