Use and Toxicity of Pyrethroid Pesticides in the Central Valley, California
Erin L. Amweg; Donald P. Weston; Nicole M. Ureda
Abstract
The use of pyrethroid pesticides is increasing in agriculture, commercial pest control, and in insecticides for residential consumers. In addition, there is a trend towards the use of newer and more
potent compounds. Little is known about the toxicity of sediment-associated pyrethroid residues to aquatic organisms, yet recent work has shown they are commonly found in aquatic sediments in the heavily
agricultural Central Valley of California, USA. Minimal data exist on the sensitivity of standard sediment toxicity testing species, despite two or more decades of agricultural use of these compounds.
Sediment concentrations causing acute toxicity and growth impairment to the amphipod Hyalella azteca were determined for six pyrethroids in three sediments, ranging from 1.1-6.5% organic carbon
(OC). In order of decreasing toxicity of sediment-associated residues, the compounds tested were lambda-cyhalothrin (0.45 µg/g OC), bifenthrin (average 10-d LC50=0.52 µg/g OC), deltamethrin (0.79 µg/g
OC), cyfluthrin (1.08 µg/g OC), esfenvalerate (1.54 µg/g OC), and permethrin (10.83 µg/g OC). In a sediment containing about 1% OC, most pyrethroids, except permethrin, would be acutely toxic to H. azteca
at concentrations of 4-10 ng/g dry weight, a concentration only slightly above current analytical detection limits. Growth was typically inhibited at concentrations below the LC50; animal biomass was
on average 38% below controls when exposed to pyrethroid concentrations roughly one-third to one-half the LC50. Survival data are consistent with, though do not necessarily prove, exposure of H. azteca
to pyrethroids entirely via the interstitial water rather than the particulate phase. A reanalysis of previously reported field data using these toxicity data confirms that the compounds are exceeding
concentrations acutely toxic to sensitive species in many agriculture-dominated water bodies.
Full article appeared in:
Environmental Toxicology and Chemistry (2005) 24:966-972.
Erratum in 24:1300-1301.
