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Alarm at weed-kill chemical
in water | Matthew Denholm - May 15, 2008
AUSTRALIAN regulators have allowed a widely used weed killer
to be present in drinking water at levels twice those now shown
to cause damaging genetic changes in human cells.
A new study by the University of California, San Francisco,
has found atrazine increases activity of human genes linked
to fetal growth retardation and infertility. Atrazine is used
to control weeds in forest plantations and crops such as canola,
sugarcane, maize, sorghum and lupins across Australia.
Holly Ingraham, study senior author and UCSF professor of cellular
and molecular pharmacology, told The Australian significant
effects on human placental cells were seen when exposed to as
little as 20 parts per billion of atrazine.
This is half the 40ppb atrazine health value limit under the
Australian Drinking Water Guidelines. The US has a drinking
water maximum of 3ppb for atrazine, while Europe has refused
to approve it for use.
Professor Ingraham said as a scientist she had "no agenda"
in terms of regulation, but she believed Australia's health
value of 40ppb was "worrying".
"If it were me drinking water, I would want it as low as
possible," she said.
The study also exposed zebrafish to the chemical, finding significant
effects at 2ppb and changes to sex ratios at 20ppb.
Earlier this month, the Australian Pesticides and Veterinary
Medicines Authority announced its review of atrazine had concluded
"no changes to the existing health standards" were
needed.
This was because while atrazine had been shown to disrupt the
nervous, hormone and reproductive systems of rats, it was "unlikely
that atrazine is an endocrine (hormonal) disruptor in humans".
However, the UCSF study drew the opposite conclusion. "Our
results strongly suggest that atrazine is an endocrine disruptor
- it is indirectly estrogenic, and it most certainly has the
potential to influence reproduction, as well as other endocrine
functions," Professor Ingraham said.
Endocrine disruptors affect the body's hormonal system, potentially
affecting growth, development and reproduction.
"Would a fetus or child be especially sensitive to this
herbicide? Probably. Our study shows that some of the genes
targeted by atrazine have already been linked to intrauterine
growth retardation and infertility."
APVMA public affairs manager Simon Cubit said the regulator's
decision not to toughen atrazine restrictions was based on "weight-of-evidence"
from many studies.
However, APVMA had sought expert advice from Australia's Office
of Chemical Safety and drawn its attention to Professor Ingraham's
study.
The Health and Medical Research Council said it would consider
"all the latest evidence" as part of its review of
drinking water guidelines.
Atrazine producer Syngenta did not comment but has insisted
the product poses no risk to human health.
Tasmanian GP Alison Bleaney, who believes atrazine may be linked
to high rates of cancer and auto-immune disease, demanded an
urgent regulatory rethink.
"One would hope that our regulators would be protecting
us and protection means occasionally that you have to take a
stand on the balance of probabilities," she said. "And
the balance of probabilities has shown for some years that atrazine
is not a safe chemical to have in our environment."
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