News Release

U.S. Department of the Interior
U.S. Geological Survey

        Address:
Office of Communication
119 National Center
Reston, VA 20192
Release
May 30, 2007
Contact         Phone
Gary Fellers    415-464-5185
Donald Sparling         618-559-5461
Catherine Puckett       352-264-3532

Research Finds That Breakdown Products of Widely Used Pesticides are
Acutely Lethal to Amphibians

The breakdown products (oxons) of the three most commonly used
organophosphorus pesticides in California's agricultural Central
Valley -- chlorpyrifos, malathion and diazinon -- are 10 - 100 times
more toxic to amphibians than their parent compounds, which are
already highly toxic to amphibians, according to experiments conducted
by scientists of Southern Illinois University, Carbondale, and the
U.S. Geological Survey (USGS) Western Ecological Research Center.

The results of the laboratory experiments on the toxicity of three
breakdown products were just published in the journal Environmental
Pollution.

"Since some of the parent pesticide compounds are already at
concentrations sufficient to cause significant amphibian mortality in
the Sierra Nevada, the higher toxicity of the breakdown products poses
a serious problem," said Dr. Gary Fellers, coauthor of the study.

Dr. Donald Sparling, a research biologist and contaminants specialist
at Southern Illinois University, and Fellers, a research biologist and
amphibian specialist at the USGS Western Ecological Research Center in
California, conducted laboratory tests to determine the acute toxicity
-- the lethal dosage causing death in 96 hours or less -- of
chlorpyrifos, malathion and diazinon, and their oxon derivatives on
tadpoles of the foothill yellow-legged frog (Rana boylii).

Organophosphorus pesticides have been implicated in the declines of
several amphibian species in the California Central Valley and in
downwind montane areas, including the Cascades frog, California red-
legged frog, mountain yellow-legged frog and the foothill yellow-
legged frog, which inhabit foothill or montane regions east of the
Central Valley.

More than 6 1/2 million pounds of active ingredient organophosphorus
pesticides were used in California during 2004, the most recent year
for which data are available. Researchers estimate that this accounts
for about 25 percent of organophosphorus pesticide use nationwide.

Organophosphorus pesticides suppress an enzyme called
acetylcholinesterase, which is essential for the proper functioning of
the nervous system. Reduced levels of acetylcholinesterase cause
neurological synapses to fire repeatedly and uncontrollably, leading
to death, usually by asphyxiation as the animal loses respiratory
control. Most pesticides of this group reach their greatest potencies
when metabolized internally and converted to an oxon form in the
liver. However, oxons can also be found in the environment, formed by
bacterial decay of the parent pesticide.

For the laboratory experiments, tadpoles were raised from eggs
collected from a stream in the California Coast Range, upwind of
agricultural activities in the Central Valley and away from areas
where significant quantities of pesticides are used. Test results
indicated that chloroxon killed all tadpoles and was at least 100
times more toxic than the lowest concentration of the parent compound
chlorpyrifos, which resulted in no mortality. Maloxon was nearly 100
times more toxic than malathion, and diazoxon was about 10 times more
toxic than diazinon.

"Other data published in 2001 and new unpublished data show that these
pesticides are widespread, even in pristine areas of the Sierra Nevada
Mountains," Sparling said. "The combination of field and laboratory
studies is revealing that organophosphorus pesticides are posing
serious hazards to the welfare and survival of native amphibians in
California."

The authors noted that amphibians inhabiting ponds in the Central
Valley of California could be simultaneously exposed to two or all
three of these pesticides and their oxons. "Because of this," said
Sparling, "the potential for interactive effects of these chemicals
needs to be explored."

Organophosphorus pesticides form the largest group of chemicals used
in the control of pests, including invertebrates, vertebrates and, to
a lesser extent, plants. Some 200 organophosphorus pesticides
available in this class have been formulated into thousands of
different products for use in agriculture, forests, gardens, homes and
industrial sites.

The title of the article in Environmental Pollution is "Comparative
toxicity of chlorpyrifos, diazinon, malathion and their oxon
derivatives to larval Rana boylii."

USGS provides science for a changing world. For more information,
visit www.usgs.gov.

Subscribe to USGS News Releases via our electronic mailing list or RSS
feed.

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Links and contacts within this release are valid at the time of
publication.

http://www.usgs.gov/newsroom/article_pf.asp?ID=1684

 ==============================

_________________________________________________________________________________

RESTON, VA.
May 30, 2007 10:08am
http://www.centralvalleybusinesstimes.com/stories/001/?ID=5272

. Commonly used in Central Valley
. 'Posing serious hazards to native amphibians'

The breakdown products of the three most commonly used organophosphorus pesticides in the Central Valley are 10 to 100 times more toxic to amphibians than their parent compounds, which are already highly toxic to amphibians, says a report Wednesday from the U.S. Geological Survey.

"Since some of the parent pesticide compounds are already at concentrations sufficient to cause significant amphibian mortality in the Sierra Nevada, the higher toxicity of the breakdown products poses a serious problem," says Gary Fellers, coauthor of the study published in the journal Environmental Pollution.

Donald Sparling, a research biologist and contaminants specialist at Southern Illinois University, and Mr. Fellers, a research biologist and amphibian specialist at the USGS Western Ecological Research Center in Sacramento, conducted laboratory tests to determine the acute toxicity -- the lethal dosage causing death in 96 hours or less -- of chlorpyrifos, malathion and diazinon, and their breakdown, or "oxon" derivatives on tadpoles of the foothill yellow-legged frog.

Organophosphorus pesticides have been implicated in the declines of several amphibian species in the Central Valley and in downwind areas, including the Cascades frog, California red-legged frog, mountain yellow-legged frog and the foothill yellow-legged frog, which inhabit foothill regions east of the Central Valley, the scientists say.

More than 6.5 million pounds of organophosphorus pesticides were used in California during 2004, the most recent year for which data are available. Researchers estimate that this accounts for about 25 percent of such pesticide use nationwide.

Organophosphorus pesticides suppress an enzyme called acetylcholinesterase, which is essential for the proper functioning of the nervous system. Reduced levels of acetylcholinesterase cause neurological synapses to fire repeatedly and uncontrollably, leading to death, usually by asphyxiation as the animal loses respiratory control, the USGS says.

Most pesticides of this group reach their greatest potencies when metabolized internally and converted to an oxon form in the liver. However, oxons can also be found in the environment, formed by bacterial decay of the parent pesticide.

For the laboratory experiments, tadpoles were raised from eggs collected from a stream in the California Coast Range, upwind of agricultural activities in the Central Valley and away from areas where significant quantities of pesticides are used. Test results indicated that chloroxon killed all tadpoles and was at least 100 times more toxic than the lowest concentration of the parent compound chlorpyrifos, which resulted in no mortality, the USGS report says.

Maloxon was nearly 100 times more toxic than malathion, and diazoxon was about 10 times more toxic than diazinon.

"Other data published in 2001 and new unpublished data show that these pesticides are widespread, even in pristine areas of the Sierra Nevada mountains," says Mr. Sparling. "The combination of field and laboratory studies is revealing that organophosphorus pesticides are posing serious hazards to the welfare and survival of native amphibians in California."

The authors note that amphibians inhabiting ponds in the Central Valley could be simultaneously exposed to two or all three of these pesticides and their oxons. "Because of this," says Mr. Sparling, "the potential for interactive effects of these chemicals needs to be explored."

Organophosphorus pesticides form the largest group of chemicals used in  the control of pests, including invertebrates, vertebrates and, to a lesser extent, plants. Some 200 organophosphorus pesticides available in this class have been formulated into thousands of different products for use in agriculture, forests, gardens, homes and industrial sites.

Copyright Central Valley Business Times © 2007