Conflict on Common Herbicide's Effects on Frogs
By CAROL KAESUK YOON
the release of a flurry of new results in what is becoming an increasingly
intense debate, scientists still have not reached a consensus as
to whether the nation's most commonly used herbicide is harming
amphibians in the wild.
new studies raise questions about whether atrazine, used primarily
for killing weeds in cornfields, is acting as an endocrine disrupter
in amphibians, interfering with normal hormonal functions, and causing
males to become hermaphrodites, producing eggs in their testes.
Some 60 million to 70 million pounds of atrazine are applied each
year in the United States, and it has been found in rivers, ponds,
snowmelt and rainwater.
have taken a particular interest in the new studies because such
a widespread endocrine disrupter could help explain worldwide declines
studies could also affect continued use of atrazine. The Environmental
Protection Agency is reviewing the herbicide's environmental risks
as part of the periodic reregistration process required for continued
sale of such chemicals.
of the newest research was presented yesterday at the Society of
Environmental Toxicology and Chemistry in Salt Lake City.
controversy began in April when Dr. Tyrone Hayes, an endocrinologist
at the University of California at Berkeley, and colleagues published
results in The Proceedings of the National Academy of Sciences indicating
that very low concentrations of atrazine, similar to those seen
in the wild, could turn males of the African clawed frog into hermaphrodites
in the laboratory.
last month in Nature, Dr. Hayes and colleagues published studies
showing that males of the leopard frog, a native species, could
also be feminized by exposure to low levels of atrazine in the laboratory.
More worrisome, the researchers found that in the seven field sites
from Utah to Iowa where they could detect atrazine, they also found
hermaphroditic frogs. At the one site without detectable atrazine,
there were no hermaphrodites.
industry-sponsored studies, carried out by a team that has been
critical of Dr. Hayes's work, have failed to replicate the findings
with the clawed frog. The work was paid for by Syngenta, a maker
of atrazine. Yesterday the team also reported that it had examined
wild-caught males of the clawed frog where it is native in Africa
and where atrazine is widely used and found no hermaphrodites.
information should be replicable," said Dr. Ronald Kendall,
an environmental toxicologist at Texas Tech University and a leader
of the industry-sponsored team.
Hayes said he was surprised by the high levels of hermaphroditism
caused by sometimes minute levels of atrazine, with sometimes as
many as one-third of the males affected. The effects were less severe
at higher levels of the herbicide. But while that might seem counterintuitive,
Dr. Hayes said it was typical for chemicals affecting hormones to
have highly different, even opposite effects at increased levels.
Kendall said his team's work had been wrongly impugned as biased
because of its industry financing, and he pointed out that Dr. Hayes
also formerly received Syngenta financing. Dr. Hayes said his original
research showing that atrazine could create hermaphroditic frogs
was sponsored by Syngenta, which never published the work. The April
publication in which he replicated that research was sponsored by
the National Science Foundation; the Nature study was paid for by
the W. Alton Jones Foundation, which finances environmental work,
and the conservation group WWF.
note: what Kendall fails to acknowledge here is that Syngenta/EcoRisk
discouraged Hayes from taking his results public once it reached
the point that implications for atrazine were clear. This was a
time when EPA was in the midst of a large scale review of atrazine,
and results showing such extraordinary biological sensitivity to
the compound would have been very damaging.
resistance from Syngenta/EcoRisk, Hayes disassociated from them,
obtained independent funding, replicated the work, submitted it
to peer-review and then published it in Proceedings
of the National Academy of Sciences. Kendall and his team, in
contrast, continue to work with Syngenta defending atrazine and
have tried repeatedly to discredit Hayes, largely via "science
through press release," referring to their work via statements
to the press but not allowing independent scientists to analyze
remains unclear why the studies conflict.
Hayes, when interviewed, had seen only one of the Kendall team's
unpublished studies. Based on the methods, Dr. Hayes said he was
not surprised they had not replicated his results. He said that
the researchers had raised the frogs under unhealthy conditions
and that they did not properly control levels of atrazine in the
note: an extraordinary percentage of the Syngenta team's animals
failed to metamorphose and those that did were tiny compared to
normal animals, apparently having starved. The statistical analysis
of their work mysteriously changed between versions, moreover, in
ways that decreased the significance of the results. The attempt
to use these flawed lab experiment as legitimate science should
be regarded as a professional embarrassment to the individuals whose
names appear on the paper. Those names, at least in the version
submitted to the US EPA docket, are: James A. Carr, Angie Gentles,
Ernest E. Smith, Wanda L. Goleman, Lina J. Urquidi, Kerry Thuett,
Ronald J. Kendall, John P. Giesy, Tim S. Gross , Keith R. Solomon
, and GlenVan Der Kraak].
if their animals were healthy, you can't compare them to our study,"
Dr. Jim Carr, comparative endocrinologist at Texas Tech and a member
of Dr. Kendall's team, said that in another study team members had
mimicked Dr. Hayes's experimental conditions more closely but still
did not produce his results.
[This study has not become available for independent analysis;
this is most likely more science via press release.] Dr.
Carr and colleagues have also criticized Dr. Hayes's omission of
certain experiments considered standard.
are not a lot of details published in the Hayes work," said
Dr. Carr. "So it's hard to compare."
[EcoRisk/Syngenta approved Hayes' original laboratory protocols
and reviewed the basic results extensively. This is a disingenuous