ANTIBIOTIC DOSE: Rampant use of antibiotics in livestock, combined with widespread use of manure as fertilizer, means some lettuce, corn, potatoes and other crops carry antibiotics.
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For half a century, meat producers have fed antibiotics to farm animals to increase their growth and stave off infections. Now scientists have discovered that those drugs are sprouting up in unexpected places: Vegetables such as corn, potatoes and lettuce absorb antibiotics when grown in soil fertilized with livestock manure, according to tests conducted at the University of Minnesota.
Today, close to 70 percent of all antibiotics and related drugs used in the United States are routinely fed to cattle, pigs and poultry, according to the Union of Concerned Scientists. Although this practice sustains a growing demand for meat, it also generates public health fears associated with the expanding presence of antibiotics in the food chain.
People have long been exposed to antibiotics in meat and milk. Now, the new research shows that they also may be
ingesting them from vegetables, perhaps even ones grown on organic farms.
The 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 two years later, 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 (U.S.) agricultural land."
Manure, widely used as a substitute for chemical fertilizer, adds nutrients that help plants grow. It is often used in organic farming.
The scientists found that although their crops were only propagated in greenhouses for six weeks--far less than a normal growing season--antibiotics were absorbed readily into their leaves. If grown for a full season, drugs most likely would find their way into parts of plants that humans eat, said Dolliver.
Less than 0.1 percent of antibiotics applied to soil were absorbed into the corn, lettuce and other plants. Though a tiny amount, health implications for people consuming such small, cumulative doses are largely unknown.
"The antibiotic accumulation in plants is just another negative consequence of our animal agriculture industry and not surprising given the quantity fed to livestock," said Steve Roach, public health program director for the non-profit Food Animal Concerns Trust.
For highly processed plants such as corn, the drugs would most likely be removed, added Dolliver. But many food crops such as spinach and lettuce are not processed, only washed, allowing antibiotics to remain.
"Nobody particularly eats corn or soybean directly," said Satish Gupta, a University of Minnesota professor of soil science and study leader. "But there are crops I am much more worried about, like cabbage and lettuce, because these are leaves we eat directly and consume raw."
One finding that particularly worries food scientists is the accumulation of antibiotics within potato tubers. Tubers are an enlarged, underground stem that uptake and store nutrients from the soil. In crops like potatoes, carrots and radishes, it is the part humans eat.
"Since these tubers and root crops are in direct contact with the soil they may show a greater propensity for [antibiotic] uptake," said Gupta.
Health officials fear that eating vegetables and meat laced with drugs meant to treat infections can promote resistant strains of bacteria in food and the environment.
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8 Comments
Add CommentHm, wouldn't composting produce more antibiotic-resistant bacteria, since it works through bacterial decomposition?
Reply | Report Abuse | Link to thisThe author of this article didn't do all his homework, and the result is an un-scientific publication that is obviously written from a one-sided point of view for the following reasons:
Reply | Report Abuse | Link to thisa) the statement, "People have long been exposed to antibiotics in meat and milk," is completely false. All animal products, including meat and milk, are withheld from the food chain for a period of time (usually 3 days up to a month depending on the substance), while animals are being treated with antibiotics. EVERY gallon of milk and animal carcass sold to consumers are individually tested clear of all traces of antibiotics before making it to the food shelf.
b) Yes, antibiotics may be excreted in manure and urine, however, the levels of antibiotics used in commercial agriculture are lower than the author and his vegan sources lead us to believe. Especially those used to treat ill animals. Given that this excrement is diluted by the excrement from hundreds of healthy animals, the actual amounts would be pretty small. Also, when we look at the amounts administered to animals in comparison to this 6-week greenhouse study, where researchers pumped high levels of antibiotics to green vegetables to see what plants are capable of picking up, the affects would not even be close to comparable.
Another reason why we need tighter regulations on the widespread use of antibiotics and such (fertilizers etc). Commercialisation and agriculture has increased crop production but has also brought certain negatives. There is no perfect answer, but growing a little in the home garden helps - to reduce environmental impact and improve the health of the individual. Besides, gardening can be an enjoyable activity... (getting off topic...) :)
Reply | Report Abuse | Link to thismellon, the manure is not composted. it is applied to the ground after being hauled out of an open feedlot or pumped out of a containment facility. anyway, your statement is not accurate. perhaps you meant to ask the question, "doesn't composting serve to decompose bacteria so that it's safe to apply on crops?" composting would not CREATE antibiotic resistant bacteria. only humans do that by using antibiotics when they are not needed. typically, they are used by large animal producers to prevent disease among animals that are too closely confined to one another to begin with. they are also over-prescribed by doctors, especially pediatricians, because the public demands them even when their usage is not warranted.
Reply | Report Abuse | Link to thisEurope's farmers get on very well without livestock raised on hormones and antibiotics. Yet the USA is refusing to import some European cheeses in retalliation for tough european laws banning chemically-treated animal meat.
Reply | Report Abuse | Link to thisThis is blackmail!
Eco-steve, your assertion that "Europe's farmers get on very well without livestock raised on hormones and antibiotics" isn't as simple as you state. We need to remember that the EU has heavily subsidized their agricultural enterprises to keep keep farm size small and limit the use of artificial substances. Therefore, both animal and crop productivity is extremely low in comparison to US farm systems. The truth is that US consumers demand cheap, convenient food, and that is what is produced, because our farms are forced to be efficient. That doesn't mean the use of these products are unsafe!
Reply | Report Abuse | Link to thisThe second part of your comment has more to do with food safety and acceptance of proven measures to ensure the safety of our food supply, than a blackmail tactic. I'm guessing you are referring to irradiated beef (which, by the way, is not a "chemical", but a processing technique used to kill bacteria). The cheeses that are not imported in the US are also, by and largely, ones that are deemed a food safety hazard. Some cheese may have heavy tariff, though, as our current market is flooded with lots of cheap dairy products at the moment, therefore it doesn't make sense to import someone else's products when we can't even use our own!
would like to see a citation of the studies discussed in this article. Can anyone point me in the right direction?
Reply | Report Abuse | Link to thisCrywulff77: As a scientist myself, I applaud you for wanting to read the source material of studies rather than taking for fact something written by biased journalists!
Reply | Report Abuse | Link to thisI am having a tough time finding the refereed article that the University of Minnesota study is found in. Perhaps it hasn't yet been published but could be in edit stages. You can find some information on University research at the web page for the Department of Soil, Water, and Climate. Also, feel free to contact Dr. Satish Gupta or another faculty member at the U of MN directly!