Back to Currently in Reevaluation


DPR placed certain pesticide products containing pyrethroids into reevaluation on August 31, 2006. The reevaluation is based on recent monitoring surveys and toxicity studies revealing the widespread presence of synthetic pyrethroid residues in the sediment of both agricultural and urban dominated California waterways at levels toxic to Hyalella azteca (H. azteca). Scientists conducted sediment bioassays using H. azteca, a resident species found in some Central Valley water bodies. Scientists commonly use H. azteca, an aquatic crustacean, as an indicator of environmental health and water quality in streams, lakes, and other bodies of water. Significant toxicity was observed at numerous sites. There was a high correlation between concentrations of pyrethroids and observed toxicity. Findings further indicate that the unique physical, chemical, and toxicological properties of the pyrethroid class of chemicals contribute to their propensity to accumulate in sediment at toxic levels. Pyrethroids are synthetic insecticides. Pyrethrins, which are natural insecticides, are found in Chrysanthemum cinerariaefolium, a perennial plant with a daisy-like appearance. DPR did not include pesticide products containing naturally occurring pyrethrins in this reevaluation because pyrethrins are known to break down rapidly in the environment.

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Denise Alder
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