19 June 2003
Pesticide Faulted for Frogs' Sexual Abnormalities
By JENNIFER 8. LEE
June 18 — Scientists from the Environmental Protection Agency
say there is "sufficient evidence" to conclude that the
country's most widely used pesticide, atrazine, causes sexual abnormality
are recommending that the agency conduct more research to understand
atrazine's mechanisms and its broader impact on frog populations.
scientists noted that there had been six studies involving three
species of frogs that show a variety of defects, including frogs
with both multiple testes and multiple ovaries, when exposed to
the chemical. The scientists cautioned that the results from studies
of atrazine had not been consistent and that it was not clear at
what levels of exposure those effects occurred or how different
frog species were affected.
several studies and environmental conditions and species, atrazine
exposure did appear to be having some impact on gonadal effects,"
Tom Steeger, a scientist with the environmental agency's pesticide
office, said on Tuesday in a presentation to an independent scientific
panel convened here to assess atrazine's impact on amphibians.
hired by Syngenta, a major manufacturer of atrazine, said they drew
different conclusions from available research.
see no correlation in the adverse gonadal effects and the introduction
and use of atrazine," Glen Van der Kraak, a professor at the
University of Guelph in Winnipeg, Manitoba, said in a presentation
to the panel.
E.P.A. scientists said many of the industry-sponsored studies had
a variety of problems, including testing conditions that led to
high mortality in their frogs. The four-day hearing by the panel,
which ends on Friday, is an extension of the E.P.A.'s nine-year
review of whether atrazine poses unacceptable risks to the environment
and to public health. Later this year, the panel will make recommendations
to the agency on how to proceed.
and its byproducts are widely found at low levels in United States
waters, especially after the planting season, when rains wash the
chemical out of fields. It is popular with farmers because it is
effective and relatively cheap. Atrazine has been banned in seven
laboratory studies have linked atrazine to cancer in rats, and some
epidemiological studies show a correlation between exposure and
cancer in humans.
E.P.A. review had been moving toward renewing the agency's approval
to use atrazine. But last year, a scientist at the University of
California published two papers suggesting that low levels of exposure
to atrazine, as low as one part per 10 billion in the water, could
cause tadpoles to develop into frogs with both male and female sexual
studies, led by Tyrone B. Hayes, were published in April 2002 in
the Proceedings of the National Academy of Science and in October
2002 in Nature magazine. Dr. Hayes had originally been hired by
a consulting concern, Ecorisk, to conduct studies on atrazine on
behalf of a company that is now Syngenta. The studies ignited a
scientific and political debate, and led the environmental agency
to convene the panel to examine atrazine and its effects on amphibians.
Syngenta said it had been unable to replicate the results of Dr.
Hayes's work in company-sponsored studies. But since then, one of
the company studies was published in a journal, Environmental Toxicology
and Chemistry, and its primary author, Dr. James Carr of Texas Tech
University, said the study did result in some hermaphrodite frogs,
though at higher exposure levels than in Dr. Hayes's studies.
Hayes and other Berkeley faculty members present at meetings about
his work say that when Dr. Hayes presented his findings to a panel
of university scientists formed by Ecorisk, some of the panel members
tried to delay him from publicizing his initial findings. Other
scientists on the Ecorisk panel say any delay was intended to test
the validity of the data.
Hayes left the panel in protest in November 2000, stating in his
resignation letter that otherwise "it will appear to my colleagues
that I have been part of a plan to bury important data."
has submitted Dr. Hayes's initial work in an interim report to the
E.P.A. The company has not submitted a final report on his research
to the agency.
two papers Dr. Hayes and his co-authors published in 2002 were based
on research done without industry financing.
Pastoor, who is in charge of global risk assessment for Syngenta,
said, "There were absolutely no constraints on any of the panel
members on anything they have found."
the minutes from a January 2001 Ecorisk panel show Tim Gross, University
of Florida professor,
[ed. note... actually USGS] who is also part of the Ecorisk panel,
telling Dr. Hayes that the "results from the contracts are
jointly owned" by the company and the scientist. "Therefore,
publication is upon mutual consent," Dr. Gross said in a letter
submitted at the meeting.
said Dr. Hayes "should be reminded of this, as well as the
confidentiality of these results."
minutes were submitted to the environmental agency and obtained
by the Natural Resources News Service through a Freedom of Information
today, Dr. Hayes spent several hours presenting his research to
atrazine discussion is a high-profile inquiry into the relatively
new scientific area of endocrine disruptors, chemicals that at minute
traces can significantly affect health by interfering with the hormones
that regulate biological activity. Several studies from the last
decade linked the trace pollutants to declining sperm counts, infertility
and various forms of cancer in humans, as well as genital malformation