Hormones: Here's The Beef Environmental Concerns Reemerge Over Steroids Given to Livestock
Science News Week of January 5, 2002
Vol. 161, No. 1
Each year, U.S. farmers raise some 36 million beef cattle.
Farmers fatten up two-thirds of these animals by using hormones.
Most cattle that go through feedlots receive steroids to
boost their growth rate and beefiness. T. Thrift, Univ. of Fla.
Many cattle are fed the same muscle-building
androgens—usually testosterone surrogates—that some athletes consume. Other
animals receive estrogens, the primary female sex hormones, or progestins,
semiandrogenic agents that shut down a female's estrus cycle. Progestins fuel
meat-building by freeing up resources that would have gone into the reproductive
cycle.
While federal law prohibits people from self-medicating with
most steroids, administering these drugs to U.S. cattle is not only permissible
but de rigueur.
So far, almost all concern about this practice has focused
on whether trace residues of these hormones in the meat have human-health
consequences. But there's another way that these powerful agents can find their
way into people and other animals. A substantial portion of the hormones
literally passes through the cattle into their feces and ends up in the
environment, where it can get into other food and drinking water.
Some scientists say that it's time to better manage
livestock's hormone-laced waste stream, which has flowed unabated in North
America for decades.
Cancer Threat
As much as anyone, John A. McLachlan knows what's been
happening. He first became interested in livestock hormones in the early 1970s,
when he learned that farmers were giving the synthetic hormone
diethylstilbestrol (DES) to chickens and cattle. This synthetic estrogen
chemically castrates male animals, enabling them to grow faster. At the time,
McLachlan's own studies at the National Institute of Environmental Health
Sciences (NIEHS) used animal models to investigate why DES fostered the
development of cancer in daughters of women treated to avoid miscarriages.
While McLachlan wasn't worried about any cancer threat that
DES might pose to animals destined for the slaughterhouse, he recalls being
very concerned that the animals' excretions were releasing "something like
13 tons of DES a year into the environment." He and others began fearing
that the hormones might pose chronic risks to wildlife and people.
Although the Food and Drug Administration (FDA) outlawed
veterinary use of DES by the mid-1970s, the provision of other hormones to
livestock continued to bother McLachlan. So, he convened a 1980 symposium to
explore this and related issues.
For the meeting, he coauthored a paper with the late David
P. Rall, then director of NIEHS. "We were prescient," McLachlan now
says. He and Rall reasoned that with all the steroid hormones being prescribed
not only to livestock but also to people—such as to women for birth control or
postmenopausal therapy—excretions of these drugs must be substantial. The
economic incentive for farmers to use the hormones—it can amount to a 40-fold
return on their investment—is compelling (see “The Financial Lure of
Hormones,”below) and will probably fuel the practice for some time.
"We said we wouldn't be surprised if significant
amounts of pharmaceutical [including veterinary] estrogens end up in
water," remembers McLachlan, now director of the Center for
Bioenvironmental Research, which is administered jointly by Tulane and Xavier
Universities, both in New Orleans. Recent data have confirmed that human
hormonal drugs do taint rivers and streams—sometimes in amounts that adversely
affect fish (SN: 6/17/00, p. 388: http://www.sciencenews.org/20000617/fob1.asp
).
Soon after the 1980 meeting, interest in the environmental
fate of livestock hormones faded as researchers got caught up in the discovery
that pesticides and other industrial chemicals could mimic and disrupt normal
hormone and endocrine action in people and other animals (SN: 7/3/93, p. 10).
Indeed, although he is a biologist specializing in
reproduction and hormonelike substances, Bernard Jegou notes that until 3 years
ago, he had never heard people discuss excreted livestock hormones.
"Considering that the weakest of these [steroid] growth
promoters is probably 100 to 1,000 times stronger in biological activity than
the most potent of the [industrial] endocrine disrupters gaining interest, I
figured these drugs could pose a real environmental threat," says Jegou,
who's the director of research at INSERM (the French Institute of Health and
Medical Research) in Rennes.
Shared Concerns
At a May 2000 meeting in Copenhagen, Jegou finally
encountered other researchers who shared his concerns. A host of speakers at
the meeting described steroid data that they were beginning to acquire as part
of studies in the United States and Europe funded under a new European Union
(EU) research program.
Since 1988, concerns about the potential health risks of
drug residues has led the EU to ban importation of the meat of hormone-treated
animals. The United States and Canada, which produce such meat, have vigorously
fought the ban through both punitive tariffs on various imports from Europe and
appeals to the World Trade Organization. The EU has expressed hope that new
research will provide scientific grounds to rebut these challenges to its
ban.
In one of the EU-funded studies, research teams led by Louis
J. Guillette Jr. of the University of Florida and Ana M. Soto of Tufts
University School of Medicine in Boston collaboratively investigated the
environmental fate of hormones running off feedlots in Nebraska.
Soto compared the hormonal activity of water sites
downstream of feedlots with that of water collected upstream. In her tests, she
added water samples to cells that react in various ways to steroids. In one
assay, estrogen turns on cell growth; in another, androgens inhibit cell
growth.
At the Copenhagen meeting, Soto reported finding that
concentrations of estrogenic pollutants at two of the downstream sites were
sometimes almost double those at the upstream site. And water from all three
downstream sites was significantly more androgenic than the samples collected
upstream. One downstream sample exhibited nearly four times the androgenicity
of the upstream water.
Bumps on the head (above) mark a reproductively active male
fathead minnow. Female (middle) sports no such bumps—unless it has been exposed
to an androgenic pollutant such as trenbolone (bottom). Photos: Ankley et al.
2001
Toxicologist L. Earl Gray Jr. with the Environmental
Protection Agency in Research Triangle Park, N.C., has also analyzed water from
those Nebraska sites. He uses a different assay for androgenicity, but like
Soto, he finds evidence of masculinizing steroids.
The steroids may not be just sitting benignly in the water.
In a report that he has just sent to the EU, Guillette reports adverse hormonal
changes in fathead minnows.
Males just downstream of the feedlots "had a
significantly reduced testis size"—which, he says, appears to explain why
they also produced less testosterone than males upstream. He also found that
the heads of these fathead minnows weren't all that fat—which also makes sense,
he notes, since testosterone helps determine skull size.
What appears to be happening, he says, is that the
waterborne androgens provide some signal that tells the males' bodies to
produce less testosterone. In females, the researchers observed a significant
increase in the ratio of androgenic to estrogenic hormone concentrations in
blood. The biological significance remains unknown.
These observations indicate that wild fish "are being
nailed by polluting hormones," Guillette told Science News—with males
becoming somewhat feminized and females somewhat masculinized.
He says that he'd wanted to compare feedlots that use
hormones and those that don't, but he couldn't find any operations that don't
take advantage of the drugs. Moreover, because Soto has not yet identified the
particular steroids in down-stream waters, Guillette notes, "we can't rule
out that these effects are due to natural androgens and estrogens in
manure." Even untreated cattle, horses, and chickens excrete natural
estrogens, testosterone, and other steroids (SN: 11/3/01, p. 285: http://www.sciencenews.org/20011103/note15.asp
).
However, Guillette adds, when one considers new German data
on how long steroidal growth-promoting drugs can persist in the environment,
"it's highly likely that what we're seeing in these wild fish is a
pharmaceutical effect" derived from the farm use of these agents.
Hormonal Holsteins
Much of the German data to which Guillette refers appears in
the November 2001 Environmental Health Perspectives. It comes from EU-funded
studies at the Technical University of Munich in Freising-Weihenstephan.
Scientists there experimentally treated Holsteins with two
growth-promoting steroids commonly used at U.S. feedlots. Andreas Daxenberger
and his colleagues inserted implants of trenbolone acetate—an androgen—into the
ears of 41 males and females and gave feed laced with melengestrol acetate, a
progestin, to another 12 females that had never been pregnant. Then, the
researchers had the dirty work of collecting and analyzing all of the manure
that these animals produced—some 100 tons—over the next 2 months.
Their trenbolone data showed that by the end of the study,
10 percent of the androgen had passed right through the animals into feces,
Daxenberger says. The animals shed similar amounts of the progestin feed
additive.
The Munich scientists then looked at how well the steroids
survived in manure. During storage of the manure, both drugs resisted bacterial
breakdown, each showing a half-life of some 260 days. Once spread on fields,
however, the hormones' degradation rate skyrocketed.
For instance, once liquefied manure was applied to fields,
the trenbolone disappeared within a little more than a week. The androgen in
dried-dung fertilizer disappeared in about 2 months. However, Daxenberger
notes, what share of the drugs' disappearance might be the result of
runoff—versus microbial breakdown—remains an open question.
Scientists at two Environmental Protection Agency
laboratories have just begun investigating what trenbolone-laced runoff might
do.
In castrated male rats, Gray finds, trenbolone stimulates
the growth of androgen-dependent tissues. However, he says, "it didn't
behave exactly like testosterone," the primary natural androgen. For
instance, while trenbolone stimulated muscle development, it had relatively
little impact on prostate growth.
He says the unexpected differences "mean that we can't
predict exactly what the drug would do in [wildlife]—especially during their
development." Gray reported his findings in November 2001 at the annual
meeting in Baltimore of the Society of Environmental Toxicology and
Chemistry.
At that meeting, Gerald T. Ankley of EPA's lab in Duluth,
Minn., described preliminary data on fish exposed to trenbolone for 21 days in
the lab. The most visible change, he noted, was the development of head bumps,
known as tubercles, on female fathead minnows. These bumps ordinarily show up
only on breeding males. The exposed females also produced fewer eggs than
unexposed females do. His lab is now looking for more subtle changes.
Even the excretion of natural steroids by livestock that are
raised without artificial hormones can have negative impacts on aquatic
animals, observes Eva Oberdîrster of Southern Methodist University in Dallas.
For example, while at Clemson (S.C.) University, she and her colleagues
analyzed field runoff of estrogen-laced manure from a small herd of pregnant
and lactating cows that had not received any hormones. Samples of the runoff
boosted blood concentrations of the egg-yolk protein vitellogenin in female turtles
at nearby ponds.
Inducing these turtles to become "superfemales"
could prove harmful, she worries, if they divert unhealthy amounts of energy
into egg production.
One of Oberdîrster's students, Lisa K. Irwin, found that the
ponds' enrichment with bovine estrogen also prompted juvenile sunfish to make
egg-yolk protein—even though these males and females were all well below an age
when even females normally do so.
Useful Studies
With a European ban on the use of steroid drugs in
livestock, why does the EU fund studies on environmental impacts of such use?
One answer comes from data amassed by Rainer Stephany of the National Institute
of Public Health and the Environment in Bilthoven, the Netherlands.
Though Europe's beef industry maintains that no steroids are
used, Stephany says that his lab and others have demonstrated by analyzing meat
samples that the continent hosts an "illegal—black market—use of growth
promoters."
A "defensible overall estimate for the use of these
compounds in the European Union, based on results from annual regulatory
residue-testing programs, could be in the range of 5 to 15 percent" of
beef cattle, he reported in the proceedings of the Copenhagen conference,
published last summer as a special, 571-page issue of APMIS (formerly Acta
Pathologica, Microbiologica et Immunologica Scandinavica).
Moreover, he notes, because all such drug treatment in
Europe is illegal, illicit users tend to employ whatever is available and
affordable. Residues of at least 35 such drugs have been found in meat samples.
This complicates screening, Stephany observes, since an investigator never
knows quite what to look for and each assay can cost as much as a cow's entire
carcass is worth. This situation contrasts sharply with that in the United
States, where drug residues in meat invariably consist of one or more of only
six FDA-approved growth promoters, he says.
Though the EU is clearly concerned about the impacts of
livestock steroids, what about U.S. regulators? At the Copenhagen meeting,
Stephen F. Sundlof, director of FDA's Center for Veterinary Medicine in
Rockville, Md., noted that although "it is my role to regulate these
substances . . . I was only made aware at this workshop that we may be having
some environmental issues to consider."
That was nearly 2 years ago. In the interim, Soto and
Guillette have briefed Sundlof on their studies. Sundlof has also learned of
the German findings. From these, he now concludes that the environmental fate
of livestock-steroid use "is something that we [at FDA] are definitely
concerned about."
"My sense," he told Science News, "is that
right now [FDA is] going to be looking into the whole issue of pharmaceuticals
getting into water—and that's not just steroids, but it's also antibiotics and
some other potent chemicals."
If soon-to-be-published analyses of stream-sampling data by
the U.S. Geological Survey confirm that livestock drugs are getting into the
environment, Sundlof says, new regulations may be called for. He doesn't
envision a phase-out of livestock steroids, but he says that farmers might be
asked to assume greater diligence in managing the animals' wastes.
For now, he cautions, plenty of unanswered questions remain
about whether and how much livestock wastes contribute to pharmaceutical
pollution in U.S. waters ( SN: 4/1/00, p. 213: http://www.sciencenews.org/20000401/fob1.asp
).
Indeed, notes Rigshospitalet endocrinologist Niels
Skakkabæk, an organizer of the Copenhagen meeting, when it comes to the
environmental fate of livestock steroids, "the most frightening thing is
that we still know so little."
The Financial Lure of Hormones Cow receives a
controlled-release hormone implant (above and below). Photos: B. Sand and T.
Thrift, Univ. of Fla.
Each year, U.S. farmers send 30 million head of cattle to
feedlots. This is where animals get beefed up on high-protein chow. To enhance
the animals' production of muscle—that is, meat—livestock producers treat 80
percent of all feedlot cattle with steroid hormones.
Some cows get steroids in their feed. Others receive one or
more hormones via a controlled-release implant in their ears. Economically,
these hormones offer a bonanza.
It costs farmers about $1 to $3 per head to treat their
livestock with either procedure, notes animal scientist Michael J. Fields of
the University of Florida in Gainesville. Treatment increases animals' growth
by 20 percent, so each cow in a feedlot typically gains 3 pounds per day, he
says. Moreover, for each pound that it gains, it consumes 15 percent less feed
than an untreated animal does.
Farmers use an injection gun to insert steroid pellets into
an ear. Because some 30 percent of the drug may remain in the ear at slaughter,
this tissue might well be discarded as hazardous waste.
"This feed efficiency works out to a cost savings of
about $40 per head—so you get more protein at a cheaper cost," Fields
says.
The Center for Veterinary Medicine at the Food and Drug
Administration has approved the use of these hormones because they tend to
leave only small concentrations—ones believed to be harmless—in meat. However,
the regulators haven't considered what effects the hormones might have after
being excreted into the environment.—J.R.
References:
Grayl, L., et al. 2001. In vivo and in vitro androgenic
effects of beta trenbolone, a potential feed-lot effluent contaminant. Society
of Environmental Toxicology and Chemistry annual meeting. Nov. 11-15.
Baltimore.
Irwin, L.K., S. Gray, and E. Oberdörster. 2001. Vitellogenin
induction in painted turtle, Chrysemys picta, as a biomarker of exposure to
environmental levels of estradiol. Aquatic Toxicology 55(Nov. 1):49.
Schiffer, B., A. Daxenberger, et al. 2001. The fate of
trenbolone acetate and melengestrol acetate after application as growth
promoters in cattle: Environmental studies. Environmental Health Perspectives
109(November):1145.
Skakkebæk, N.E. 2001. Hormone and endocrine disrupters in
food and water: Possible impact on human health. Reprints of APMIS, Supplement
No. 13, Vol. 109. Munksgaard-Copenhagen.
Stephany, R.W. 2001. Hormones in meat: Different approaches
in the EU and in the USA. APMIS 109:S357. See http://www.blackwellmunksgaard.com/apmis.
Further Readings:
McLachlan, J.A. 2001. Environmental signaling: What embryos
and evolution teach us about endocrine disrupting chemicals. Endocrine Reviews
22(June):319.
Opinion of the Scientific Committee on Veterinary Measures
Relating to Public Health. 1999. Assessment of potential risks to human health
from hormone residues in bovine meat and meat products (April 30). Available at
http://www.europa.eu.int/comm/food/fs/him/him_index_en.html.
Raloff, J. 2001. Composting cuts manure's toxic legacy.
Science News 160(Nov. 3):285. Available at http://www.sciencenews.org/20011103/note15.asp
.
2000. Excreted drugs: Something looks fishy. Science News
157(June 17):388. Available at http://www.sciencenews.org/20000617/fob1.asp
.
1995. Beyond estrogens. Science News 148(July 15):44.
1993. EcoCancers. Science News 144(July 3):10.
Sources:
Gerald T. Ankley USEPA Environmental Effects Research
Laboratory Mid-Continent Ecology Division/ORD 6201 Congdon Boulevard Duluth, MN
55804
Andreas Daxenberger Leiter Produktprufung Westendstrasse 199
80686 Munchen Germany
Michael J. Fields University of Florida Department of Animal
Sciences 459 Shealy Drive Gainesville, FL 32611
L. Earl Gray Mail Code 72 USEPA Mailroom Research Triangle
Park, NC 27711
Louis J. Guillette Jr. University of Florida 223 Bartram
Hall P.O. Box 118525 Gainesville, FL 32611
Lisa K. Irwin U.S. Fish and Wildlife Service Arkansas Field
Office 1500 Museum Road Conway, AR 72032
Bernard Jegou French Institute of Health and Medical
Research Campus de Beaulieu Avenue du general Leclerc Universite de Rennes I
35042 Rennes cedex Brittany, France
John A. McLachlan Center for Bioenvironmental Research
Tulane University 1430 Tulane Avenue New Orleans, LA 70112
Delegation of the European Commission 2300 M Street, N.W.
Washington, DC 20037
Ana Soto Tufts University School of Medicine Department of
Anatomy and Cellular Biology 136 Harrison Avenue Boston, MA 02111
Rainer W. Stephany Laboratory for Residue Analysis EU
Communities Reference Laboratory (CRL) RIVM-National Institute of Public Health
and the Environment P.O. Box 1 NL-3720 BA Bilthoven Netherlands From Science
News, Vol. 161, No. 1, Jan. 5, 2002, p. 10.
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