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Would you like drugs with that?

(article, Rebecca Kessler)

Hogs, cattle, and other farm animals get regular doses of antibiotics, most of which pass through the creatures undiminished in their germ-killing power. Antibiotic-laden manure is later spread on agricultural lands to fertilize crops, both organic and conventional. Then what happens to the drugs? Crop plants can take up antibiotics from the manure, according to a new study — and small quantities can make their way into edible leaves and tubers. 

Satish Gupta, a professor of soil science at the University of Minnesota in St. Paul, his graduate student Holly Dolliver, and a colleague conducted a small greenhouse study in which they dosed hog manure with sulfamethazine, a commonly used veterinary antibiotic, before adding it to soil in which they planted corn and lettuce seeds and potato seed tubers. Sure enough, after growing in the soil for a month and a half, the scientists found that the plant leaves contained low doses of sulfamethazine, as did a potato seed tuber. 

The amount of antibiotic in the plants was far too low to cause ill effects in healthy adults, but the scientists worry about the effects of long-term exposure in children and people with antibiotic allergies or compromised immune systems. 

Even more troubling is the possibility that a population getting a steady low dose of antibiotics in its veggies might be contributing to the development of antibiotic-resistant strains of bacteria and other nasties. And spreading antibiotics freely in the environment could be changing the balance of soil ecosystems and promoting resistance in soil bacteria that make their way up the food chain. 

Cooking your food might incapacitate certain antibiotics, but some — and there are more than a dozen veterinary antibiotics in regular use — are more stable than others. The method of cooking makes a difference too.  

The study, published in the Journal of Environmental Quality, adds to a handful of earlier studies that found similar results for other antibiotics and vegetable crops. The next step, say Gupta and Dolliver, is to do bigger experiments on fields of crops to see whether their results carry outside the greenhouse, and whether composting manure before spreading it on crops makes a difference. 

Concerns about antibiotics making their way into the food supply have so far focused on meat, milk, and other animal products. Veggies may now have to be added to the list.

Also on Culinate: An article on bovine antibiotics.