Press relese from the Alliance Communications Group
March 14, 2005
Upswing in Lesser Used, but More Potent
Pesticides in California's Central Valley
In California alone, 360 metric tons of pyrethroid pesticides
are used annually. Researchers have found a trend toward
using newer pyrethroid compounds that can be more toxic
to aquatic life.
Newswise — 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
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
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
Environmental Toxicology and Chemistry is a monthly journal of
the Society of Environmental Toxicology and Chemistry (SETAC).
For more information, visit http://www.setac.org.