[Pharmwaste] New Curse for an Old Foe (atrazine and amphibians)

[Tenace, Laurie]

http://sciencenow.sciencemag.org/cgi/content/full/2006/1208/2
New Curse for an Old Foe
By Amy Coombs
ScienceNOW Daily News
8 December 2006

Pesticides have wreaked havoc on global amphibian populations, and now new
evidence suggests that the problem may be even worse than thought. One of the
most common herbicides-atrazine-appears to have an added deadly effect: It
makes tiger salamanders more vulnerable to certain infections. Because
atrazine also has deleterious effects on humans and other mammals,
researchers fear this new effect on amphibians may be a harbinger of a larger
problem for other species.
Atrazine is the second most popular agricultural pesticide in the United
States, used primarily to control weeds on corn, sugar cane, and residential
lawns. The compound mimics the hormone estrogen, and over the past 10 years,
scientists have noticed that frogs and other amphibians exposed to the
herbicide develop deformed genitalia and smaller voice boxes, making mating
calls softer and reproduction impossible. Atrazine was introduced in 1958,
and scientists started noticing upticks in fungal and viral diseases in
exposed animals in the late 1990s. Studies confirmed that atrazine suppresses
the immune system, but whether this led to increased infection rates remained
a mystery. 

To solve the conundrum, biologists Diane Denise Forson and Andrew Storfer of
Washington State University in Pullman took a closer look at the tiger
salamander, a small amphibian commonly found in marshes and ponds around the
globe. Tiger salamanders tend to live in areas exposed to atrazine, and over
the past few years biologists have noted a rise in their susceptibility to
the Ambystoma tigrinum virus (ATV), which causes internal hemorrhaging and
death. In the lab, the researchers exposed 384 tiger salamander larvae to
levels of atrazine similar to those found in nature, and then introduced ATV
for 3 days at the 12-week larval stage. (Atrazine is commonly sprayed in the
spring, during this stage of development.)

Tiger salamanders exposed to atrazine were twice as likely to become infected
with ATV than were those not exposed to the herbicide, the team reports in
this month's issue of Ecological Applications. In addition, when combined
with sodium nitrate, a type of fertilizer, atrazine lowered the levels of
white blood cells that fight disease by nearly 20%. "Because amphibian skin
is permeable, toxins can be absorbed directly into the bloodstream," says
Storfer. "Their eggs are also permeable to environmental toxins, which makes
them indicators of environmental contamination," adds Forson.

"This is one of the few, rare examples of a toxin causing an indirect,
increased susceptibility to infection," says Andrew Blaustein, an ecologist
at Oregon State University in Corvallis. However, the specific mechanism by
which immunosuppression occurs still needs to be established, says Tyrone
Hayes, a biologist at the University of California, Berkeley. This is
especially important because atrazine has been associated with breast and
prostate cancer in humans, he says.

Laurie J. Tenace
Environmental Specialist
Florida Department of Environmental Protection
2600 Blair Stone Road, MS 4555
Tallahassee, Florida 32399-2400
PH: (850) 245-8759
FAX: (850) 245-8811
Laurie.Tenace at dep.state.fl.us  
 
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