Well, while we wait for Shelly to pry his foot out of his mouth,
a new concern has arisen for organic farmers.
News - January 6, 2009
Worried about Antibiotics in Your Beef? Vegetables May Be No Better
New studies show vegetables like lettuce and potatoes--even organic
ones--may carry antibiotics
By Matthew Cimitile
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
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
"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
"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.
Roach said "the clearest public health implication" from treating
livestock with antibiotics is the development of resistant bacteria that
reduces the effectiveness of human medicine. Past studies have shown
overuse of antibiotics reduces their ability to cure infections. Over
time, certain antibiotics are rendered ineffective.
Scientists believe antibiotics also may have contributed to the
explosive rise in asthma and allergies in children over the last 20
years. Researchers at Henry Ford Hospital in Detroit, following 448
children from birth for seven years, reported that children who received
antibiotics within their first six months had a higher risk of
developing allergies and asthma.
Such health concerns led the European Union in 2006 to ban antibiotic
use as feed additives for promoting livestock growth. But in the United
States, nearly 25 million pounds of antibiotics per year, up from 16
million in the mid 1980s, are given to healthy animals for agriculture
purposes, according to a 2000 report by the Union of Concerned
Livestock producers contend that the spread of resistant strains of
bacteria stems from the overuse of all medicines to treat infectious
diseases in both humans and animals. Removal of antibiotics, they say,
would only lead to increased disease in animals and reduction in food
Tainted manure can impact more than just the soil. Once applied to the
land, antibiotics can infiltrate water supplies as it seeps through the
soil into aquifers or spills into surface water due to runoff, explained
"The other thing to remember is that the field is not a sterile
environment. Mice, rabbit and foxes traverse farmland while other
animals graze, all with the potential to become vectors for the
resistant bacteria organisms and spread it throughout different animal
populations," said Pat Millner, a U.S. Department of Agriculture
microbiologist based in Maryland.
The presence of antibiotics within the food chain is likely to increase
as the U.S. Food and Drug Administration has permitted greater use of
controversial drugs on farm animals. For example, this past October, the
FDA dropped plans to halt use of cefquinome, a potent antibiotic, after
it said in July it would push against its use in animals.
Even if a product has the USDA organic label, it still can harbor traces
of antibiotics, Gupta said. While there are restrictions on use of raw
manure in U.S. organic farming because of concern over bacteria, no such
rules are in place regarding antibiotics or hormones. Not all organic
growers use manure with antibiotics, but many do, said Gupta.
High-temperature composting of manure, designed to kill pathogens, is
required for crops certified under the USDA label. That could eliminate
some antibiotics. But growers are not required to check for the drugs.
"We urgently need to find some way to put guidelines in place on organic
food regarding these chemicals," Gupta said.
Gupta said all growers should be told that composting can help.
Composting decays piles of food or manure as microbes decompose organic
matter using oxygen to survive, grow and reproduce. Heating up the
material creates conditions conducive for bacteria to break down
antibiotics and pathogens.
A pilot study by USDA scientists in Maryland added straw to a beef
cattle manure pile, heating up the dense material while allowing spaces
for air to penetrate. The higher temperatures sped up the decaying
process of harmful substances.
"The process happens very rapidly, in this study it took about 10 days,"
said Millner. "This is not too surprising since antibiotics are not a
thermally stable chemical compound."
In another study, the same researchers who discovered the uptake of
antibiotics by plants tested four of these drugs to determine how
effective composting would be in reducing harmful chemicals in turkey
manure. After 25 days using a combination of natural heat generated by
microbial activity, three of the four antibiotics broke down under the
high energy conditions created, said Dolliver.
Composting reduced concentrations of some antibiotics by up to 99
percent. "These findings suggest manure management can be an important
strategy for reducing the overall impact for these compounds making
their way into the environment," said Dolliver.
Many questions still remain. Currently, projects are underway to grow
crops for a full season in antibiotic laced manure, to grow them in
fields rather than greenhouses and to analyze the concentrations and
locations of the antibiotics within the plants. Researchers also want to
determine which antibiotics are more likely to be picked up, which
plants are more prone to uptake, what composting methods are most
effective in reducing harmful material in manure and what antibiotics
may be resistant to composting.
There are serious societal implications regarding the discoveries
already made and the questions yet to be answered, Gupta concluded. "We
are a chemical society and humans are the main user of pharmaceutical
products," said Gupta. "We need a better understanding of what takes
place when chemicals are applied to sources of food and must be more
vigilant about regulating what we use to grow food and what we put in
This article originally ran at Environmental Health News, a news source
published by Environmental Health Sciences, a nonprofit media company.
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