376 (SHA-1117-664582) Risk Assessment Approach to Evaluate Exposure and Risk from Agricultural and Urban Uses of Pyrethroids.
Start time: 1:50 PM
Shamim, M¹, Rexrode, M¹, Melendez, J¹, Parker, R¹, ¹ Environmental Protection Agency, Washington, DC, USA
The Environmental Protection Agency has completed its screening-level ecological risk assessments for a number of synthetic pyrethroids relative to their use on agricultural crops (e.g., cotton, corn, wheat) and urban settings (e.g., mosquito abatement use). These assessments show that pyrethroids pose a potential risk to aquatic species, including fish, invertebrates, and sediment-dwelling organisms. Furthermore, pyrethroid bioavailability is not expected to be completely mitigated through adsorption to sediments and particulate matter. Because of the toxicity, mode of action, high partition coefficients (K_ocs), and moderate to high persistence of this class of compounds, the Agency considered pyrethroid bound sediments as an important aquatic exposure component. In the absence of data, the Agency estimated sediment toxicity values by using the equilibrium partitioning method (EqP) for extrapolating sediment/pore water exposure values. This method is based on the assumption that partitioning of pyrethroids between sediment organic carbon and pore water is at equilibrium. The estimated toxicity values in conjunction with model generated sediment/pore water exposure values were used to calculate the Risk Quotients (RQs). In its assessment of this class of compounds, the Agency also used an innovative modeling approach involving the spray drift model AGDISP coupled with the surface water model PRZM/EXAMS to predict potential exposure and risk to aquatic ecosystems from pyrethroid mosquito abatement uses. The effect of spray drift and the use of buffer zones in reducing exposure to bodies of water adjacent to treated areas was also investigated. This abstract has been subjected to review by EPA's Office of Pesticide Programs and was approved for submission. Approval does not signify the contents reflect the views of EPA, nor does mention of trade names or commercial products constitute endorsement or recommendation for use.

377 (HOL-1117-835568) National Exposure Analysis of Pyrethroids (Part 1); Spatial Proximity of Agriculture to Surface Water.
Start time: 2:10 PM
Holmes, C¹, Matella, M¹, ¹ Waterborne Environmental, Inc., Leesburg, VA, USA
This three-part presentation describes a national exposure analysis that was undertaken to characterize watersheds in the conterminous US for relative risk to pyrethroid exposure. Part 1 relates to the quantification of spatial proximity of agriculture to surface water as an indicator of potential exposure from agricultural spray drift. Surface water from the National Hydrography Dataset (NHD) was separated into four classes and the area proximate to each class was generated in a GIS. The National Land Cover Dataset (NLCD) was used to determine the spatial location of agricultural land, and how much of this crop area was proximate to surface water. In addition, the 2002 Census of Agriculture was used to provide information on the specific crop types (e.g., corn, cotton) and the area grown within each county. These datasets were combined to estimate the amount of corn and cotton grown within close proximity to surface water (up to 480m). Finally, over 60,000 watersheds from the USGS Enhanced River Reach File dataset were combined with the crop proximity information to generate a distribution of potential exposure from corn and cotton to surface water within each watershed. The results represent a national distribution of potential spray drift exposure suitable for identifying areas for detailed analysis. In addition, they provide the ability to place detailed analysis results into the broader context of US agriculture and potential surface water exposure. The spatial results of this study could be used with additional crops, alternate land cover data, or alternate watersheds. Subsequent presentations will describe the potential exposure to surface water related to erosion risk, and also an examination of the relative sensitivities to pyrethroid exposure for both spray drift and erosion factors.

378 (WES-1117-831595) A tale of two creeks: An intensive study of pyrethroids and related toxicity in urban environments.
Start time: 2:30 PM
Weston, D¹, Holmes, R², English, T¹, ¹ University of California, Berkeley, CA, USA² Central Valley Regional Water Quality Control Board, Rancho Cordova, CA, USA
Pleasant Grove Creek and its tributaries drain an area of dense housing subdivisions in Roseville CA. The Kirker Creek watershed encompasses residential, commercial and industrial areas of Pittsburg, CA. Both systems were intensively studied with analysis of sediments for pesticides, sediment toxicity testing with Hyalella azteca, and in the case of Pleasant Grove Creek, sampling for resident H. azteca. Findings in both systems were very similar. From the point where the creeks enter developed areas, nearly all sediment samples contained pyrethroid insecticides at several times the acutely lethal level concentration for H. azteca. Total or near total mortality was observed in toxicity tests throughout both systems. Resident H. azteca were present in those portions of Pleasant Grove Creek with minimal development, but were absent from the most affected reaches. Toxicity Identification Evaluation procedures suggested pyrethroids were major contributors to the toxicity. Of the group, bifenthrin was the dominant contributor, though acutely toxic levels of cypermethrin, cyfluthrin and deltamethrin often occurred. Residential areas appeared to be the principal source for all these pyrethroids, and we were able to rule out significant inputs from agriculture or mosquito control. Use of outdoor pest control products by homeowners and structural pest control by professional applicators were the probable sources of pyrethroids to both creek systems.

379 (AMW-1117-745405) Pyrethroid pesticide distribution and toxicity in urban creeks.
Start time: 2:50 PM
Amweg, E¹, You, J², ¹ University of California, Berkeley, Berkeley, CA, USA² Southern Illinois University, Carbondale, IL, USA
Pyrethroid pesticides are replacing organophosphates for many urban applications, including structural pest control, landscape maintenance, and for residential home and garden use. Past monitoring of pesticides in urban-dominated creeks has focused on the water column because the relative water solubility of organophosphates. Pyrethroids are highly sediment-associated however, and sediment quality in urban creeks has received little attention. The present study intends to determine if pyrethroids are detectable in urban systems and if concentrations are high enough to cause associated aquatic toxicity. A total of 15 California creeks and 12 Tennessee creeks were tested for pesticide residues in the sediments, and aquatic toxicity was determined by acute toxicity tests using the amphipod, Hyalella azteca . In California, 13 of the 15 creeks tested were toxic on at least one sampling occasion, and sediment pyrethroid concentrations were sufficient to explain the observed toxicity in most cases. None of the Tennessee creeks were toxic, and pyrethroids were rarely detectable above 1 ng/g. Distributions of individual pyrethroids are presented and potential explanations for the regional differences are discussed.

(58882) break.
Start time: 3:10 PM

380 (LYD-1117-740135) Relative contributions of agricultural or urban pyrethroid usage to toxicity in California streams.
Start time: 3:50 PM
Lydy, M¹, Weston, D², You, J¹, ¹ Southern Illinois University, Carbondale, IL, USA² University of California-Berkeley, Berkeley, CA, USA
Due to the increasing regulatory restrictions on organophosphate pesticides, pyrethroid pesticides have replaced the organophosphates for many residential and agricultural uses. Urban use of pyrethroids, in particular, has increased significantly due to professional pest control and retail sales for home usage. This study was designed to compare and contrast agricultural and urban usage of pyrethroids and the resulting toxicity noted in these two landscapes. About 150 agricultural sediment samples and 50 urban samples were taken from water bodies throughout California. These sediments were analyzed for 28 pesticides including chlorpyrifos, 20 organochlorine insecticides, and the following pyrethroids: bifenthrin, lambda-cyhalothrin, deltamethrin, esfenvalerate, permethrin, cyfluthrin and cypermethrin. Acute toxicity tests (10-day) with Hyalella azetca were also conducted on all samples. Nearly 80% of the agricultural sediments contained measurable pyrethroid concentrations, while 100% of the urban samples contained pyrethroids. Of these samples, 70% of the urban sites were acutely toxic to H. azetca, and 20% of the agricultural sites were toxic. Using a toxic unit approach, it was found that pyrethroids were likely the sole or major contributor to much of the toxicity in both landscapes. In addition, all of the tested pyrethroids had higher median and maximum concentrations in urban versus agricultural sites. The relative composition of the pyrethroids differed, however, with esfenvalerate often detected in the agricultural setting, while bifenthrin and cyfluthrin dominated the urban samples. The data show that agricultural use of pyrethroids may be causing more widespread toxicity to aquatic invertebrates simply because of the greater amount of land devoted to agriculture in the study area, but the magnitude of pyrethroid concentrations and severity of toxicity is often greater in urban environments.

381 (DOB-1117-556378) The toxicity of synthetic pyrethroids to freshwater and estuarine sediment dwelling organisms.
Start time: 4:10 PM
Putt, A¹, Dix, M¹, Tavano, J¹, Dobbs, M², PWG, ³, ¹ Springborn Smithers Laboratories, Wareham, MA, USA² Bayer CropScience, Research Triangle Park, NC, USA³ Bayer Crop Science, Du Pont Crop Protection, FMC Corporation, Pytech Chemicals GmbH, Valent USA Corporation, Syngenta AG
Nine sediment toxicity tests were conducted with four synthetic pyrethroids, bifenthrin, cyfluthrin, cypermethrin, and esfenvalerate, under GLP following EPA standard methods. Separate 10-day sediment toxicity tests (EPA Test Method 100.2) were conducted with all four compounds in the same freshwater sediment to evaluate the impact on survival and growth of the freshwater midge larvae, Chironomus tentans. In addition, a life cycle test (EPA Test Method 100.5) was conducted with cypermethrin in the same freshwater sediment to evaluate the impact on survival, growth, emergence and reproduction of C. tentans. Separate 28-day sediment toxicity tests (EPA 600/R-01/020) were conducted with each pyrethroid in the same estuarine sediment to evaluate the impact on survival and growth on the estuarine amphipod, Leptocheirus plumulosus. LC50, EC50 and No-Observed Effect Concentrations were calculated based on measured sediment concentrations. In the 10-day midge studies, LC50 values ranged from 280 to >2500 g/kg, while EC50's ranged from 220 to 780 g/kg. Growth was the most sensitive parameter in the midge life-cycle study with clear effects seen in body weight at 100 g/kg. L. plumulosus, with a 28-d exposure, was in general more sensitive then C. tentans (10 days) with LC50 values in the range of 34 and 240 g/kg, and EC50's in the range of 36 to 150 g/kg. Trends regarding species and parameter sensitivity will be discussed as well as expression of results in a manner more reflective of the bioavailable fraction (e.g., sediment concentrations normalized for sediment organic carbon).

382 (HUN-1117-822276) Bioavailability of pyrethroids in sediment: Estimated with.
Start time: 4:30 PM
Hunter, W¹, Yang, W¹, Gan, J¹, ¹ University of California Riverside, Riverside, CA, USA
Synthetic pyrethroid insecticides (SPs) are being increasingly used in agriculture and urban environments as a replacement for the organophosphate insecticides. Recent studies show presence of SPs in sediments from various locations in California. Pyrethroids have high acute toxicity to a broad spectrum of aquatic organisms, and thus, it is imperative to understand the ecotoxicological implications of SPs in water-sediment environments. Because SPs have high affinity for sediment and DOM, their bioavailable concentrations in sediment environments are expected to be significantly lower than the total chemical concentration. Measurement of bioavailable concentrations of SPs will likely allow better prediction of toxicity from chemical concentrations, and improve our understanding of factors affecting sediment toxicity. In this study, the bioavailability of permethrin and cyfluthrin to Chironomus tentans larvae in water-sediment systems was investigated. During the bioassays, polydimethylsiloxane (PDMS) fibers were used as a "biomimetic" tool and simultaneously exposed to the same samples as the organisms. The freely dissolved concentration (C_w) in the sediment porewater was estimated from pesticide accumulation in the PDMS fiber. The C_w estimated by the PDMS fiber was only a small fraction of the total pore water concentration. Uptake of SPs by C. tentans generally followed the same trend as pesticide accumulation in the PDMS fiber, and both decreased with increasing organic matter content in the bulk sediment or in the porewater. Also, LC50 values increased with increasing OM content, and was conversely correlated with PDMS-measured concentrations. These results suggest that only the dissolved fraction of SPs in the sediment was bioavailable to C. tentans, and the bioavailability was likely dependent on sediment properties, especially the OM content.

383 (DEL-1117-565334) Toxicity of the pyrethroid insecticide permethrin to adult and larval grass shrimp (Palaemonetes pugio).
Start time: 4:50 PM
DeLorenzo, M^{1, 3}, Serrano, L^{2, 3}, Hoguet, J³, Chung, K³, Key, P³, ¹ University of South Carolina, Columbia, SC, USA³ NOAA, National Ocean Service, Charleston, SC, USA² College of Charleston, Grice Marine Biology Program, Charleston, SC, USA
The use of pyrethroid insecticides is increasing as these compounds are replacing organophosphates in agricultural and urban settings. Along the southeast coast of the U.S., pyrethroids are commonly used for mosquito control, agricultural crop protection, and home pest control; resulting in significant potential for contamination of the estuarine environment. Synthetic pyrethroids are neurotoxins, affecting both target and nontarget organisms. Toxicity of the pyrethroid insecticide permethrin was assessed using three life stages of the estuarine grass shrimp, Palaemonetes pugio. Adult and larval shrimp were tested using a 96-hour static renewal aqueous test without sediment, and a 24-hour static nonrenewal aqueous test with sediment. For the embryos a 96-hour static renewal aqueous test without sediment was conducted. Two cellular stress biomarkers, glutathione and lipid peroxidation, were also assessed using the adult and larval life stages. Larval shrimp were more sensitive than adults, with a 96h LC50 value of 0.05 g/L (95% confidence interval (CI) of 0.04-0.05 g/L), compared to 0.25 g/L (95% CI: 0.21-0.31) for adults. Grass shrimp embryos were least sensitive to permethrin, with a 96h LC50 value of 3.70g/L. Permethrin exposure increased the time to hatch in embryos, although a dose-response relationship with concentration was not observed. Changes in swimming behavior were observed at the highest concentration for newly hatched larvae in the embryo test (6.4 g/L), and for larvae in the aqueous larval toxicity test (0.2 g/L). Glutathione levels increased with permethrin exposure, while lipid peroxidation values decreased. The presence of sediment significantly decreased the toxicity of permethrin to both adult and larval grass shrimp. These results indicate that very low levels of permethrin may negatively affect individual grass shrimp health and survival. Permethrin use in the coastal zone should be carefully managed to avoid adverse impacts on non-target estuarine organisms.

384 (COA-1117-844827) Toxicology of synthetic pyrethroids to fish.
Start time: 5:10 PM
Coats, J¹, ¹ Iowa State Univ, Pesticide Toxioclogy Lab, Dept Entomology, Ames, Iowa, USA
Natural pyrethrins have considerable toxicity to fish, as well as aquatic arthropods. However their highly labile character results in very rapid dissipation in most natural waters. Modern synthetic, so-called photostable pyrethroids are also much more stable in aquatic or marine systems than the original natural pyrethrins; they are also more toxic to fish (and aquatic arthropods) than the natural pyrethrins. The synthetic pyrethroids, however, exhibit low levels of acute toxicity to birds and mammals. Our research focused on explaining the high toxicity to fish, compared to the low toxicity to birds and mammals, and it resulted in determining several contributing factors. Toxicokinetic factors were examined: uptake efficiency, distribution in the body, biotransformation, and elimination. Potential secondary mechanisms of action were investigated, especially the possible impact of hardness and salinity on osmoregulation. Uptake rate for a highly lipophilic halogenated synthetic pyrethroid was actually lower than for most other pesticides. Biotransformation deficiencies in several species of fish, especially in ester hydrolysis, accounted for some of the discrepancy between fish and higher vertebrates. Elimination also seemed to progress more slowly in fish. Stresses on osmoregulation are able to contribute as a secondary mechanism of action. Selective toxicity of diastereomers and determination of concentrations in brains at time of death (and exposure concentrations or doses causing death) revealed that other toxicodynamic differences also exist between fish and the higher vertebrates. Concentrations in bird and rat brains at death were significantly higher than concentrations in fish brains at death. In summary, multiple toxicokinetic and toxicodynamic factors contribute to the acute susceptibility of fish to synthetic pyrethroid insecticides.