Spatial Analysis of Bifenthrin Sediment Concentrations in California Waterbodies from 2001 to 2010: Identification of Toxic and Non-Toxic Areas

The objective of this article is to summarize and map bifenthrin sediment measurements from California waterbodies from 2001 to 2010 to show sites where bifenthrin has been measured in sediment (including both detected and non-detected concentrations) and where corresponding toxicity or its lack has been reported or predicted. Bifenthrin measurements were available from depositional areas at 359 sites with concurrent total organic carbon (TOC) measurements in California waterbodies and values from approximately 37% of these sites were below the level of detection. Sediment toxicity data based on Hyalella azteca single species ambient toxicity tests were available for 268 sites with concurrent bifenthrin measurements and 62% of these sites showed no significant toxicity. Sixteen percent of the 140 California sites with non-detected bifenthrin concentrations had some significant sediment toxicity thus suggesting that toxicity at these sites is due to factors other than bifenthrin. One percent TOC normalized bifenthrin measurements reported from 268 sites showed no predicted significant toxicity at 83% of the sites based on a comparison with a Hyalella azteca acute value of 6.1ng/g while 99.3% of the sites showed no predicted significant toxicity based on a Chironomus tentans acute toxicity value of 177.5ng/g. The test species toxicity data (i.e., Hyalella or Chironomus) used to predict bifenthrin toxicity in the field is therefore critical as the use of Hyalella toxicity data (a highly sensitive species to bifenthrin) may be overprotective and this species is less representative of most California waterbodies when compared with Chironomids.