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Media Resources :: Newsroom
Upswing in Lesser Used, But
More Potent Pesticides in California's Central Valley
14 March 2005
In California alone, 360 metric tons of pyrethroid
pesticides are used annually. University of California-Berkeley
researchers have conducted a study to determine the
harmful effects of this class of pesticides on aquatic
organisms through sediment residues. What they have
found is a trend toward using newer compounds that can
be more toxic to aquatic life. The study appears in
the April issue of Environmental
Toxicology and Chemistry.
Increased monitoring of organophosphates resulted in
a call for decreased use of these once popular pesticides.
This may have only allowed for them to be replaced with
pyrethroids. Peaking in 1993, pyrethroid use in the
state's agricultural system declined in the 1990s but
has shown a 25% increase in the past few years. Of the
five pyrethroids used in 1993, permethrin accounted
for 60%. In 2002, the number of pyrethroid compounds
in use doubled to 10, but permethrin declined to 45%
of the total. Newer compounds were found to be 20 times
more toxic than permethrin.
The team of researchers studied six pyrethroids in
three sediments taken from California's Central Valley,
where two-thirds of the state's cropland is found. Study
results showed acute toxicity and growth impairment
in the amphipod Hyalella azteca, a sensitive test species.
Animal biomass was roughly 38% below that of the control
group when exposed to pyrethroid levels that were one-third
to one-half of the lethal concentration. Except for
permethrin, most pyrethroids would be acutely toxic
to H. azteca at concentrations only slightly above detection
limits. The six compounds tested in order of decreasing
toxicity were bifenthrin, lambda-cyhalothrin, deltamethrin,
esfenvalerate, cyfluthrin and permethrin.
Little research exists on the use and toxicity of pyrethroids
and their prevalence in sediments despite the finding
that sediments are likely the primary reservoir for
environmental residues-not the dissolved phase as in
previous studies. With increasing use of pyrethroids
in agriculture, residences and commercial pest control,
further study of sediment-associated residues is necessary
to determine their ecological impact.
The study's authors are Erin L. Amweg, Donald P. Weston
and Nicole M. Ureda of the Department of Integrative
Biology at the University of California-Berkeley.
To read the entire study, click here: http://www.allenpress.com/pdf/entc_24_414_966_972.pdf
Environmental Toxicology
and Chemistry is a monthly journal of the Society
of Environmental Toxicology and Chemistry (SETAC). For
more information about the Society, visit www.setac.org.
For more information about Environmental
Toxicology and Chemistry, visit http://setac.allenpress.com.
[Use and Toxicity of Pyrethroid
Pesticides in the Central Valley, California, USA, Environmental
Toxicology and Chemistry] 2005; Vol. 24 (4);966-972
Contact:
April M. Phillips
T 850 469 1500 x 28
aprilp@setac.org
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