Unwanted antibiotics could be finding their way to you
by Don Gordon
It is no secret that overuse of antibiotics may foster a buildup of disease causing organisms that are resistant to the chemicals used to control them.
That’s why many doctors are reluctant to prescribe these chemicals except when absolutely necessary.
But exposure to antibiotics may come from other sources. For example, according to the Union of Concerned Scientists, nearly 70 percent of the antibiotics produced in the United States are fed to livestock. That means if you are a meat eater and/or drink milk, you may be getting an unwanted dose of these chemicals.
Now, here is the really bad news. Even if you are a vegetarian, there is no escaping these antibiotics because new research conducted at the University of Minnesota confirms that we may be getting unwanted antibiotics from plants. Matthew Cimitile, writing in Environmental Health News, reports researchers found that common vegetables absorbed antibiotics when grown in soil fertilized with livestock manure.
Chlortetracycline, an antibiotic widely used to treat livestock diseases, was found in corn, green onions and cabbage that were grown on manure-treated soils. Corn, lettuce and potatoes were found to contain the antibiotic sulfamethazine after they were grown in soil fertilized with liquid hog manure. The researchers also found that as the concentration of antibiotics increased in the manure, the amount absorbed by the plants also increased.
Scientists estimate that about 90 percent of the antibiotics fed to animals are excreted through urine or manure. Only a small amount of the antibiotics found in manure-laden soils is absorbed by plants, and the long term health effects for people consuming small doses is unknown. They estimate that in highly processed food, antibiotics are likely to be removed, but vegetables that are consumed raw such as lettuce and cabbage are of more concern. Plants with large underground edible storage organs such as the roots of carrots or the tubers of potatoes are also problematic.
If treating livestock with antibiotics leads to resistant bacteria, some scientists believe it is time to limit their use. For example, Cimitile reports that in 2006 the European Union banned antibiotic use as feed additives for promoting livestock growth. But in this country there seems to be no slowdown in their use.
The Union of Concerned Scientists reports that each year we give 25 million pounds of antibiotics to healthy animals. Demand for more antibiotic use has probably increased because of the way we now raise animals. Disease problems are now more likely to occur in confined quarters in contrast to the time when animals were raised on the open range.
Other than limiting the use of antibiotics, what are the alternatives for agriculture?
No one has suggested eliminating the use of manure because of its beneficial effects for soil. It is also an important fertilizer source for organic farmers.
Composting manure is a viable option for reducing antibiotic levels because antibiotics are not thermally stable compounds. In one study reported in Journal of Environmental Quality, composting reduced concentrations of three antibiotics by 54 percent to 99 percent, but one, sulfamethazine, was not affected.
In addition to antibiotics in meat, milk and plants, most of these drugs are highly soluble and they can end up in aquifers or surface waters. It is also important to realize that we aren’t the only species to suffer from overuse of antibiotics. Many animals may feel the effects of resistant bacteria, and they may become vectors for spreading diseases.
Don Gordon is professor emeritus of botany at Minnesota State University, Mankato.
It is no secret that overuse of antibiotics may foster a buildup of disease causing organisms that are resistant to the chemicals used to control them.
That’s why many doctors are reluctant to prescribe these chemicals except when absolutely necessary.
But exposure to antibiotics may come from other sources. For example, according to the Union of Concerned Scientists, nearly 70 percent of the antibiotics produced in the United States are fed to livestock. That means if you are a meat eater and/or drink milk, you may be getting an unwanted dose of these chemicals.
Now, here is the really bad news. Even if you are a vegetarian, there is no escaping these antibiotics because new research conducted at the University of Minnesota confirms that we may be getting unwanted antibiotics from plants. Matthew Cimitile, writing in Environmental Health News, reports researchers found that common vegetables absorbed antibiotics when grown in soil fertilized with livestock manure.
Chlortetracycline, an antibiotic widely used to treat livestock diseases, was found in corn, green onions and cabbage that were grown on manure-treated soils. Corn, lettuce and potatoes were found to contain the antibiotic sulfamethazine after they were grown in soil fertilized with liquid hog manure. The researchers also found that as the concentration of antibiotics increased in the manure, the amount absorbed by the plants also increased.
Scientists estimate that about 90 percent of the antibiotics fed to animals are excreted through urine or manure. Only a small amount of the antibiotics found in manure-laden soils is absorbed by plants, and the long term health effects for people consuming small doses is unknown. They estimate that in highly processed food, antibiotics are likely to be removed, but vegetables that are consumed raw such as lettuce and cabbage are of more concern. Plants with large underground edible storage organs such as the roots of carrots or the tubers of potatoes are also problematic.
If treating livestock with antibiotics leads to resistant bacteria, some scientists believe it is time to limit their use. For example, Cimitile reports that in 2006 the European Union banned antibiotic use as feed additives for promoting livestock growth. But in this country there seems to be no slowdown in their use.
The Union of Concerned Scientists reports that each year we give 25 million pounds of antibiotics to healthy animals. Demand for more antibiotic use has probably increased because of the way we now raise animals. Disease problems are now more likely to occur in confined quarters in contrast to the time when animals were raised on the open range.
Other than limiting the use of antibiotics, what are the alternatives for agriculture?
No one has suggested eliminating the use of manure because of its beneficial effects for soil. It is also an important fertilizer source for organic farmers.
Composting manure is a viable option for reducing antibiotic levels because antibiotics are not thermally stable compounds. In one study reported in Journal of Environmental Quality, composting reduced concentrations of three antibiotics by 54 percent to 99 percent, but one, sulfamethazine, was not affected.
In addition to antibiotics in meat, milk and plants, most of these drugs are highly soluble and they can end up in aquifers or surface waters. It is also important to realize that we aren’t the only species to suffer from overuse of antibiotics. Many animals may feel the effects of resistant bacteria, and they may become vectors for spreading diseases.
Don Gordon is professor emeritus of botany at Minnesota State University, Mankato.
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