http://www.truthout.org/issues_06/printer_100907EB.shtml
New
Study Shows Genetically Engineered Corn Could Pollute Aquatic
Ecosystems
Environmental News Network
Monday 08 October 2007
Bloomington, Indiana - A study by an Indiana University environmental science
professor and several colleagues suggests a widely planted variety of
genetically engineered corn has the potential to harm aquatic ecosystems. The
study is being published this week by the journal Proceedings of the National
Academies of Sciences.
Researchers, including Todd V.
Royer, an assistant professor in the IU School of Public and Environmental
Affairs, established that pollen and other plant parts containing toxins from
genetically engineered Bt corn are washing into streams near cornfields.
They also conducted laboratory trials that found
consumption of Bt corn byproducts produced increased mortality and reduced
growth in caddisflies, aquatic insects that are related to the pests targeted by
the toxin in Bt corn.
Caddisflies, Royer said, "are a
food resource for higher organisms like fish and amphibians. And, if our goal is
to have healthy, functioning ecosystems, we need to protect all the parts. Water
resources are something we depend on greatly."
Other
principal investigators for the study, titled "Toxins in transgenic crop
byproducts may affect headwater stream ecosystems," were Emma Rosi-Marshall of
Loyola University Chicago, Jennifer Tank of the University of Notre Dame and
Matt Whiles of Southern Illinois University. It was funded by the National
Science Foundation.
Bt corn is engineered to include
a gene from the micro-organism Bacillus thuringiensis, which produces a toxin
that protects the crop from pests, in particular the European corn borer. It was
licensed for use in 1996 and quickly gained popularity. In 2006, around 35
percent of corn acreage planted in the U.S. was
genetically modified, the study says, citing U.S. Department of Agriculture
data.
Before licensing Bt corn, the U.S.
Environmental Protection Agency conducted trials to test its impact on water
biota. But it used Daphnia, a crustacean commonly used for toxicity tests, and
not insects that are more closely related to the target pests, Royer said.
Royer emphasized that, if there are unintended
consequences of planting genetically engineered crops, farmers shouldn't be held
responsible. In a competitive agricultural economy, producers have to use the
best technologies they can get.
"Every new technology
comes with some benefits and some risks," he said. "I think probably the risks
associated with widespread planting of Bt corn were not fully assessed."
There was a public flap over the growing use of Bt
corn in 1999, when a report indicated it might harm monarch butterflies. But
studies coordinated by the government's Agriculture Research Service and
published in PNAS concluded there was not a significant threat to monarchs.
Around that time, Royer said, he and his colleagues wondered whether the toxin
from Bt corn was getting into streams near cornfields; and, if so, whether it
could have an impact on aquatic insects.
Their
research, conducted in 2005 and 2006 in an intensely farmed region of northern
Indiana,
measured inputs of Bt corn pollen and corn byproducts (e.g., leaves and cobs) in
12 headwater streams, using litter traps to collect the materials. They also
found corn pollen in the guts of certain caddisflies, showing they were feeding
on corn pollen.
In laboratory trials, the researchers
found caddisflies that were fed leaves from Bt corn had growth rates that were
less than half those of caddisflies fed non-Bt corn litter. They also found that
a different type of caddisfly had significantly increased mortality rates when
exposed to Bt corn pollen at concentrations between two and three times the
maximum found in the test sites.
Royer said there was
considerable variation in the amount of corn pollen and byproducts found at
study locations. And there is likely also to be significant geographical
variation; farmers in Iowa and Illinois, for example, are planting more Bt corn than
those in Indiana. The level of Bt corn pollen
associated with increased mortality in caddisflies, he said, "could potentially
represent conditions in streams of the western Corn
Belt."
University of Illinois at
Urbana-Champaign August 22, 2007
Team Tracks Antibiotic Resistance From
Swine Farms To Groundwater
Science Daily — The routine
use of antibiotics in swine production can have unintended consequences, with
antibiotic resistance genes sometimes leaking from waste lagoons into
groundwater.
A research team tracked
the movement of tetracycline resistance genes from wastewater lagoons to
groundwater at two Illinois hog farms. Red circles mark the
locations of groundwater testing wells on Site A, the more impacted facility.
The lagoon is unlined. (Credit: Photo couttesy R.I. Mackie)
In
a new study, researchers at the University of Illinois report that some genes found in
hog waste lagoons are transferred – "like batons" – from one bacterial species
to another. The researchers found that this migration across species and into
new environments sometimes dilutes – and sometimes amplifies – genes conferring
antibiotic resistance.
The new report, in the August issue of Applied and
Environmental Microbiology, tracks the passage of tetracycline resistance genes
from hog waste lagoons into groundwater wells at two Illinois swine
facilities.
This is the first study to take a broad sample of
tetracycline resistance genes in a landscape dominated by hog farming, said
principal investigator R.I. Mackie. And it is one of the first to survey the
genes directly rather than focusing on the organisms that host them. Mackie is a
professor in the department of animal sciences and an affiliate of the Institute
for Genomic Biology.
"At this stage, we're not really concerned about
who's got these genes," Mackie said. "If the genes are there, potentially they
can get into the right organism at the right time and confer resistance to an
antibiotic that's being used to treat disease."
Tetracycline is widely
used in swine production. It is injected into the animals to treat or prevent
disease, and is often used as an additive in hog feed to boost the animals'
growth. Its near-continuous use in some hog farms promotes the evolution of
tetracycline-resistant strains in the animals' digestive tracts and manure.
The migration of antibiotic resistance from animal feeding operations
into groundwater has broad implications for human and ecological health. There
are roughly 238,000 animal feeding operations in the U.S., which
collectively generate about 500 million tons of manure per year. Groundwater
comprises about 40 percent of the public water supply, and more than 97 percent
of the drinking water used in rural areas.
Federal law mandates that
animal facilities develop nutrient management plans to protect surface water and
groundwater from fecal contamination. Most swine facilities hold the effluent in
large, water-filled lagoons until it can be injected into the ground as
fertilizer. Thanks to a change in the law in the late 1990s, new lagoons must be
built with liners to prevent seepage. Swine facilities in operation prior to the
new regulations are allowed to continue using unlined lagoons, however.
Some of these lagoons leak.
The researchers extracted bacterial
DNA from lagoons and groundwater wells at two study sites over a period of three
years. They screened these samples for seven different tetracycline resistance
genes.
They found fluctuating levels of every one of the seven genes for
which they screened in the lagoons. They also found that these genes were
migrating from the lagoons to some of the groundwater wells.
It should
be noted that many genes that confer antibiotic resistance occur naturally in
the environment. Tetracycline is itself a bacterial product, employed by
Streptomyces bacteria long before humans discovered its usefulness.
In
order to determine the origin of the tetracycline resistance genes found in the
groundwater, the researchers conducted a genetic analysis of one gene family,
tet(W), in samples from the lagoons and from groundwater wells below
(downgradient of) and above (upgradient to) the lagoons. They found that the
variants of tet(W) genes in the upgradient, environmental control wells were
distinct from those of the lagoons, while the wells downgradient of the lagoons
contained genes consistent with both the background levels and those in the
lagoons.
"There's a human impact on these sites that is superimposed on
a natural signal," said postdoctoral research assistant Anthony Yannarell, an
author on the study.
One of the two hog farms, "Site A," was more
impacted by resistance genes from the lagoon, due to its hydrogeology. The site
included two layers of sand – at about two meters and eight meters below the
surface – through which groundwater flowed.
"Every time we looked in the
lagoon, we saw all of the genes we were looking for," Yannarell said. "At Site
A, all the wells that were closest to the lagoon almost always had every gene.
As you got further from the lagoon you started to see genes dropping
out."
The resistance genes were present at much higher levels – "an order
of magnitude higher," said the authors – in the lagoon than in the contaminated
wells. Most were diluted as they moved away from the lagoons in the groundwater.
There was one notable exception. A gene known as tet(C) was found at
higher levels in some of the groundwater wells at Site A than in the lagoon. Its
heightened presence was not consistent with background levels, indicating that
something in the environment was amplifying this one gene, which had originated
in the lagoon.
Perhaps the gene had migrated to a new organism,
Yannarell said, to find a host that was more suited to conditions in the
groundwater.
"What we are seeing is that the genes can travel a lot
further than the bacteria," Mackie said. "It's a matter of getting the DNA into
the right organism. It's a relay race."
Other authors on the study are
postdoctoral research assistant S. Koike; Illinois State Geological Survey
geochemist I.G. Krapac; research assistant H.D. Oliver; USDA Agricultural
Research Service scientist and professor of crop sciences J.C. Chee-Sanford; and
visiting professor of animal sciences R.I. Aminov.
Note: This story has been adapted from a news release
issued by University of Illinois at Urbana-Champaign.